On the attribution of flood peaks

by Judith Curry

The hypothesized link between a warming climate and increased frequency and magnitude of floods goes something like this:  a warmer climate is associated with more water vapor in the atmosphere, which means more rainfall and more floods.  Is there any observational support for this link?

A series of papers on this subject have been published by Gabriele Villarini at Princeton University.  Two of the papers related to the U.S. are highlighted here.

Flood peak distributions for the eastern United States

Gabriele Villarini and James Smith

Abstract.  Annual maximum peak discharge time series from 572 stations with a record of at least 75 years in the eastern United States are used to examine flood peak distributions from a regional perspective. The central issues of this study are (1) “mixtures” of flood peak distributions, (2) upper tail properties of flood peaks, (3) scaling properties of flood peaks, (4) spatial heterogeneities of flood peak distributions, and (5) temporal nonstationarities of annual flood peaks. Landfalling tropical cyclones are an important element of flood peak distributions throughout the eastern United States, but their relative importance in the “mixture” of annual flood peaks varies widely, and abruptly, in space over the region. Winter-spring extratropical systems and warm season thunderstorm systems also introduce distinct flood peak populations, with spatially varying control of flood frequency distributions over the eastern United States. We examine abrupt changes in the mean and variance of flood peak distributions through change point analyses and temporal trends in the flood peak records through nonparametric tests. Abrupt changes, rather than slowly varying trends, are typically responsible for nonstationarities in annual flood peak records in the eastern United States, and detected change points are often linked to regulation of river basins. Trend analyses for the 572 eastern United States gaging stations provide little evidence at this point (2009) for increasing flood peak distributions associated with human-induced climate change. Estimates of the location, scale, and shape parameters of the generalized extreme value (GEV) distribution provide a framework for examining scaling properties of flood peaks and upper tail properties of flood distributions. It is shown that anomalously large values of the GEV shape parameter estimates are linked to the role of tropical cyclones in controlling the upper tail of flood distributions. Scaling analyses of flood peaks highlight the heterogeneities in flood magnitudes over the region with maxima in scaled flood magnitudes in the high-elevation Appalachian Mountains and minima in the low-gradient Coastal Plain.

(2010),  Water Resour. Res., 46, W06504, doi:10.1029/2009WR008395.  [Link]  to abstract  (paper not available online)

Pielke Jr. cites the following from the paper’s conclusions:

Only a small fraction of stations exhibited significant linear trends. For those stations with trends, there was a split between increasing and decreasing trends. No spatial structure was found for stations exhibiting trends. There is little indication that human‐induced climate change has resulted in increasing flood magnitudes for the eastern United States.

Examining Flood Frequency Distributions in the Midwest U.S.

Gabriele Villarini, James Smith, Mary Lynn Baeck, Wiltoid Krajewski

Abstract.  Annual maximum peak discharge time series from 196 stream gage stations with a record of at least 75 years from the Midwest United States is examined to study flood peak distributions from a regional point of view. The focus of this study is to evaluate: (1) “mixtures” of flood peak distributions, (2) upper tail and scaling properties of the flood peak distributions, and (3) presence of temporal nonstationarities in the flood peak records. Warm season convective systems are responsible for some of the largest floods in the area, in particular in Nebraska, Kansas, and Iowa. Spring events associated with snowmelt and rain-on-snow are common in the northern part of the study domain. Nonparametric tests are used to investigate the presence of abrupt and slowly varying changes. Change-points rather than monotonic trends are responsible for most violations of the stationarity assumption. The abrupt changes in flood peaks can be associated with anthropogenic changes, such as changes in land use/land cover, agricultural practice, and construction of dams. The trend analyses do not suggest an increase in the flood peak distribution due to anthropogenic climate change. Examination of the upper tail and scaling properties of the flood peak distributions are examined by means of the location, scale, and shape parameters of the Generalized Extreme Value distribution.

Paper No. JAWRA-10-0046-P of the Journal of the American Water Resources Association(JAWRA).  [Link]  to abstract  (paper not available online)

CO2Science provides the following summary of the paper:

What was learned
The four U.S. researchers report that in the vast majority of cases where streamflow changes were observed, they were “associated with change-points (both in mean and variance) rather than monotonic trends,” and they indicate that “these non-stationarities are often associated with anthropogenic effects.” But rather than increases in anthropogenic CO2 emissions, they cite such things as “changes in land use/land cover, changes in agricultural practice, and construction of dams and reservoirs.”

What it means
Based on their findings, and, as they note, “in agreement with previous studies” they conclude that “there is little indication that anthropogenic climate change has significantly affected the flood frequency distribution for the Midwest U.S.” And as they make doubly clear in the abstract of their paper, they say that “trend analyses do not suggest an increase in the flood peak distribution due to anthropogenic climate change.”

On the stationarity of flood peaks in the continental U.S. and Central Europe

While the journal articles disappointingly are not available online, i spotted an extensive pdf presentation by Villarini [link].  Some text excerpts:

Problem Statement and Objectives

  • There is a large spatial variability in flood hazards over the continental United States and central Europe
  • Profound anthropogenic changes (e.g., changes in land use / land cover, construction of dams, river engineering)
  • Projected increasing frequency of extreme rain and flood with human induced climate change
  • Rapidly changing flood hazards with urbanization

Central Issues:

  • temporal non-stationarities of annual flood peaks
  • changes in frequency of extreme flooding due to climate change
  • flood hazard assessment in urban environment
  • “Mixtures” of flood peaks and impact of tropical cyclones on flood peak distributions

Conclusions

  • Change-points rather than monotonic trends are responsible for the violation of the stationarity assumption.
  • Analyses of historical discharge records do not point at changes in the flood peak distribution due climate change.
  • Non-stationary modeling of flood peaks in urban environment
  • Under nonstationary conditions, alternative definitions of return period have to be sought.
  • Spatial heterogeneity in “mixtures” of flood peaks.
  • Tropical cyclones control extreme flooding in much of the eastern US. Analyses of tropical storm frequency in a warmer climate do not suggest a significant increase in tropical storms in the North Atlantic basin over the 21st century.

Trenberth on the impact of global warming on flooding                         .
From the Yale360 Forum discussed previously on this thread:                                         .
Kevin Trenberth, senior scientist at the U.S. National Center for Atmospheric Research’s Climate Analysis Section .                                                                                            .
Yes, undoubtedly. The environment in which all storms form has changed owing to human activities. Global warming has increased temperatures and directly related to that is an increase in the water-holding of the atmosphere. Over the ocean, where there are no water limitations, observations confirm that the amount of water vapor in the atmosphere has increased by about 4 percent, consistent with a 1 degree F warming of sea surface temperatures since about the 1970s. The human component does not change much from year to year and affects all storms.
.
However, the most spectacular events over the past year have been extreme heavy rains: flooding in India, China, and Pakistan in July and August, and then Queensland, Australia in December 2010 and January 2011. Further, very heavy rains in the U.S. in April 2011, along with snow melt, have also led to extensive flooding. In all these cases, very high sea surface temperatures have undoubtedly contributed to extra moisture flowing into the storms that produced the heavy rains and likely contributed to the strength of the storms through added energy. While perhaps a major part of these high sea surface temperatures was related to natural variability such as ENSO [El Nino Southern Oscillation], a component is related to global warming. It is when global warming and natural variability come together that records are broken.                                                   .
.JC comments:  Villarini’s analysis and interpretation seems pretty compelling to me, I like the methodology.  So what is wrong with the picture that Kevin Trenberth (and others) have been painting (besides the fact that they don’t seem to have looked at actual flood data)?  An increase in atmospheric water vapor associated with warmer temperatures doesn’t necessarily increase rainfall nor is it necessary that an increase in rainfall is distributed spatiotemporally to produce increased floods. It seems that whatever signal that might be found for an increase in floods from global warming is swamped by changes in land use and river engineering.                                                                                                      .                                                                                                                                                                      Moderation note:  this is a technical thread with comments moderated for relevance.
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211 responses to “On the attribution of flood peaks

  1. There appears to be no trend in precipitation over land. The data series for precipitation over oceans seems too short to be meaningful but also shows no trend. There are clear trend in specific humidity both over land and ocean. The logical conclusion to draw is that there remains more humidity in the air after it rains in warmer air and that the amount of water released during a precipitation event remians roughly equivalent regardless of the specific humidity. Also, I find it odd that climatologists would be arguing weather events. Isn’t that what they ridicule skeptics for all the time?

    http://www1.ncdc.noaa.gov/pub/data/cmb/bams-sotc/2010/bams-sotc-2010-chapter2-global-climate-lo-rez.pdf

    • Dear Steven,

      There are no sufficient precipitation gauges or data over ocean to make an educated conclusion about the total precipitation trend. Over much of the land, however, precipitation has been definitely decreasing. Moisture content in the lower Troposphere has been increasing with temperature, but at the same time, moisture content has been decreasing in the upper Troposphere. The net moisture change in the atmosphere has not changed. In fact and based on mathematics, it cannot change.

      • It would be helpful if you referenced the precipitation over land decreasing since this would appear to disagree with the reference I linked which, if there is a trend at all, would have to be very marginal. Also a reference to the net moisture content would be helpful since while I am aware of a decrease in the relative humidity, I am unaware of a decrease in the specific humidity. Thanks in advance.

      • Dear Steve,
        There is a large number of papers on this subject. Just make sure that the authors or institutions behind the publications are not “contaminated” with the politics of climate science. Here is a partial list from around the world:
        1) Calabria daily rainfall from 1970 to 2006, S. Federico et al, Natural Hazard and Earth Sciences;
        2) Compatibility analysis of precipitation and runoff trends over the large Siberian Watersheds, Svetlana Berezovskaya et al, Geophysical Research Letter vol 31, L21502
        3) A tree-Ring reconstruction of past precipitation for Baja, California sur, Mexico, Sara C. Diaz, et al, International Journal of Climatology
        4) Study of the rain intensity in Athens and Thessaloniki, Greece, C.M. Philandras et al, Advances in Geosciences.

        If you search the web, they are available for free. If you cannot find them, please contact me through my website and I will e-mail them to you. Sorry I was unable to copy their links.

        Finally, moisture content and specific humidity are the same thing. They do not change for the whole atmosphere with surface warming.

    • “There appears to be no trend in precipitation over land. The data series for precipitation over oceans seems too short to be meaningful but also shows no trend.”

      Lack of experimental evidence is no obstacle to those who accept government research funds and spout official dogma.

      For four decades public research funds flowed only to those who align their “scientific” conclusions with official dogma of NAS, PNAS, UK’s Royal Society, RS Proceedings, the UN’s IPCC, Nature, Science, BBC, PBS, Time magazine, Newsweek, the Norwegian Nobel Prize Committee, etc.

      ACC (anthropologic climate change), AGW (anthropologic global warming), SSM-HFS (standard solar model of H-fusion stars), OSN (oscillating solar neutrinos), BBU (big bang universe) are a few examples of politically-correct, consensus science dogma that violate experimental data and observations.

      By a strange coincidence the response of world leaders and scientific organizations to Climategate exposed the plan adopted in secrecy by international agreement between East and West on 21-28 Feb 1972 to save the world from the danger of annihilation in nuclear warfare by compromising the integrity of government funded science.

      http://dl.dropbox.com/u/10640850/20110722_Climategate_Roots.doc

      http://dl.dropbox.com/u/10640850/20110722_Climategate_Roots.pdf

      Now, four decades later, we have physically survived in an increasingly totalitarian world government with tightly controlled information.

      Thanks to Climategate and the brave souls who challenged fraudulent science, our civil rights and the integrity of science may yet be restored.

      • Dear Oliver,

        I respectfully have to disagree with you. Precipitation over much of the land has been decreasing. There is a large number of publications available on the web that confirms the reduction. Please ensure that the authors or institution behind the publications are not “contaminated” by the politics of climate science.

      • Nabil– Can you reference a link that supports your conclusion? I am not writing that you are wrong, but I am not aware of any definitive data to support your conclusion.

      • Dear Rob,
        There is a large number of papers on this subject. Just make sure that the authors or institutions behind the publications are not ‘contaminated” with the politics of climate science. Here is a partial list from around the world:
        1) Calabria daily rainfall from 1970 to 2006, S. Federico et al, Natural Hazard and Earth Sciences;
        2) Compatibility analysis of precipitation and runoff trends over the large Siberian Watersheds, Svetlana Berezovskaya et al, Geophysical Research Letter vol 31, L21502
        3) A tree-Ring reconstruction of past precipitation for Baja, California sur, Mexico, Sara C. Diaz, et al, International Journal of Climatology
        4) Study of the rain intensity in Athens and Thessaloniki, Greece, C.M. Philandras et al, Advances in Geosciences.

        If you search the web, they are available for free. If you cannot find them, please contact me through my website and I will e-mail them to you. Sorry I was unable to copy their links.

      • Nabil

        I am sorry, but what you are writing does not make sense as a conclusion. A review of the change in rainfall in a specific area is without meaning individually. It does not show a trend overall. To write that it is raining less is location “A” certainly does not mean or prove that it is raining more or less overall.

      • Dear Rob,

        I am not writing, others are. We go by the available observations and they show a reduction in precipitation. When observations agree with theory and mathematics, then it becomes an undisputed fact.

        The fact is that, where river watersheds accumulate snow or permafrost, there is positive river runoffs in spite of the fact that precipitation is decreasing, contrary to the conventional wisdom, but in agreement with mathematics. The observed positive river runoffs is correlated to the rise in carbon dioxide emissions-its supported by observations and mathematics.

      • Nabil

        Because you believe something or write something does NOT make it correct. Writing that “some areas” are dryer or “many areas” are getting less rainfall is without meaning statistically. (which I am reasonably sure you know). The overall data I am familar with does not agree with what you have written. Do you have some study that can confirm what you have written?

      • Dear Rob,
        I am responding here because your last comment for some reason did not have the reply button. Please take a look at Article-7, global warming in the Siberian Watersheds posted on my website: http://www.global-heat.net. If you wish to read more, please read Article-12, Earth’s Magic and book pdf. When you are done, please let me know what you think.

      • Dear Rob,
        I operated a weather station and the present reduction of about 0.8 mm annually can be measured easily, if attention is paid. In the last 50 years, average precipitation reduction has been about 0.5 mm annually, which can be measured as well. It is easy to spot precipitation trend in area where precipitation is small say 250 mm annually or less. It will be harder to spot a trend in precipitation say in India, Philippines, Louisiana, or Illinois, where annual rainfall is in meters.

      • Nabil
        When I read that you are an engineer, I had hopes that what you wrote would logically make sense, unfortunately I was greatly disappointed. There was nothing in what you wrote that even reasonably supported the conclusion that higher levels of humidity will lead or has lead to lower rainfall.
        You also wrote conclusions such as “Climate change are warming and cooling cycles caused by variations in Mesopause temperature over extended periods of time.” Which are not necessarily correct.

        Sorry, but I am left wanting after reading your work, but perhaps other will disagree.

      • Dear Rob,

        You are absolutely right! The earth system does not go by conventional wisdom or the known logic. And all of the practical engineering applications and experiments that we have are for quick and practical processes, not for a rise of 0.0000002 degrees centigrade per hour. Therefore, we expect a different logic when dealing with the Earth system.

        Our knowledge with the earth system is so poor to the point that we do not know how summer and winter occur, for no one has ever calculated the seasons, let alone the climate. The reason is that we have not considered Menopause temperature in our climate science yet.

      • Nabil

        I agree with some of what you have written.

        I agree that we lack a great deal of knowledge regarding the impacts of the many of the earth’s climate system variables. At this stage, I am not highly confident that we even know all the variablies, much less the weightings of each in relation to one another.

        That is one of the reasons why I suggest that it would be better understand the data before jumping to conclusions. Some people’s solutions are very harmful

      • Dear Mondo,

        As discussed earlier with Rob, we use mathematics to feel things when our other senses cannot reach far or deep enough. Mathematics suggests that the value of Mesopause temperature sets the rate of precipitation. There is a lot of mathematics to prove it, which is is presented on my website http://www.global-heat.net. When Mesopause temperature decreases such as in summer or when carbon dioxide emissions increases, precipitation decreases. When Mesopause temperature increase such as in winter or following a major volcanic events, precipitation rate increases. These observations are well documented and available on the web for free.

        Of course, variables such as volcanic eruptions and ENSO change precipitation rate, but these are cycles whose effects cancel out within seven to ten years. And precipitation rate maintains around an average value. This average has a trend (or climate trend) whose value has been decreasing due to carbon dioxide emissions. The reason is that Carbon dioxide has a molecular weight that is larger than that of air and Mesopause temperature decreases with the rise in the concentration of carbon dioxide.

        Similarly, dust and other equal variables impact weather conditions, but they have no impact on climates. Antarctic ice core data show clearly that only carbon dioxide affected past climates. This was true then and must be true now. Therefore, only carbon dioxide can impact the long-term trend in precipitation.

      • Dear Rob,

        Exactly! There is so much we do not know about the Earth and there is still research missing in order to fully understand how the atmosphere works. However, when our senses could not reach far or deep enough, we always resorted to mathematics, and it helped in the past. That is why I am using mathematics, and I am hoping that I’m barking on the right tree. Opinions like yours matter to me. Thank you for exchange.

      • Nabil,

        What confuses me about your statements is that you seem to be arguing that local or regional changes in precipitation are due to “climate change” caused by anthropogenic CO2 emissions.

        But there is a lot of information that local and regional changes in precipitation can reflect land-use changes such as deforestation, interference with natural hydrological processes, construction of dams which change river flow dynamics, irrigation practices and numerous other anthropogenic factors. In some parts of the world there is strong documented evidence for land-use changes causing desertification (US Dust Bowl of the 1930s for example).

        How do we figure out if observed changes in precipitation reflect natural cycles (El Nino, La Nina for example), anthropogenic land-use impacts, anthropogenic CO2 emissions or other factors known and unknown?

      • Dear Mondo,
        I’m copying my reply from above, sorry for that.

        As discussed earlier with Rob, we use mathematics to feel things when our other senses cannot reach far or deep enough. Mathematics suggests that the value of Mesopause temperature sets the rate of precipitation. There is a lot of mathematics to prove it, which is is presented on my website http://www.global-heat.net. When Mesopause temperature decreases such as in summer or when carbon dioxide emissions increases, precipitation decreases. When Mesopause temperature increase such as in winter or following a major volcanic events, precipitation rate increases. These observations are well documented and available on the web for free.

        Of course, variables such as volcanic eruptions and ENSO change precipitation rate, but these are cycles whose effects cancel out within seven to ten years. And precipitation rate maintains around an average value. This average has a trend (or climate trend) whose value has been decreasing due to carbon dioxide emissions. The reason is that Carbon dioxide has a molecular weight that is larger than that of air and Mesopause temperature decreases with the rise in the concentration of carbon dioxide.

        Similarly, dust and other equal variables impact weather conditions, but they have no impact on climates. Antarctic ice core data show clearly that only carbon dioxide affected past climates. This was true then and must be true now. Therefore, only carbon dioxide can impact the long-term trend in precipitation.

      • Dear Mondo,

        This is a follow-up: The record shows that earth surface went through cycles of green and arid coverage, yet climate cycles went on anyway. Similarly, ice coverage retreated and expanded, but the cycles repeated anyway, and there was no such a thing as energy balance runoffs. In short, past experience suggests that earth’s albedo played minimal role, if any, in climate change. Only carbon dioxide changed climates.

    • Alternate hypothesis: warmer air holds more water, and is reluctant to let it go unless in contact with a substantial cold air mass. So the latter is the “forcing driver”.

      Incompatible data point: the air isn’t warmer.

  2. Flood peaks should not be confused with damage, or otherwise human deaths.

    This is one of Al Gore’s arguments regarding Rio de Janeiro, in his Climate Reality Project. It should not be confused with precipitation data, which has been much bigger in the past, as METSUL has evidenced.

    Please see the data regarding Rio here:

    http://ecotretas.blogspot.com/2011/07/two-hours-later-in-rio.html

  3. Judith,

    Climate at best is regional events that are trying to generate an overall picture of the whole planet.
    But much of science is missing to complete the overall picture.

    Just moving around the ocean heat to a colder region does change the evaporation dynamics which again is regional events and do not effect the whole planet since the circumference of the equator is the largest distance of area. The planetary tilting makes the study more complex by changing where the angle of solar heat hits regionally.

  4. This is the usual dilemma. Trenberth and others are conjecturing from simplified first principles. The evidence does not support them but it is poor. So the science is inconclusive.

  5. Rain expresses the inability of air to keep an overflow of water vapor. As this concept relates to the temperature. the rain will stop so with relative humidity (temperatures) the same. In fact, the increased temperature means increased storage of water vapor not more rain.
    If temperatures decreases then, there is more rain.

  6. a warmer climate is associated with more water vapor in the atmosphere, which means more rainfall and more clouds

    This is the bit I’m really having trouble with. How can more clouds not affect the albedo, thereby acting as a negative feedback?

    • The surface albedo and feedbacks that increase temperature aren’t all that relevant to this argument. If you assume that the climate is warming (for whatever reason), how does the warming translate (or not) into increased flooding frequency and intensity?

      • If you look at Greenland Ice Core data, the Snow accumulation rate is much higher during warm times than during cold times. The same is true if you look at Antarctic Ice Core data. Snow accumulation rate is higher during warm times. We can disagree about why it happens, but the data shows that it does happen. Extreme Snows and Rains occur during years with Low Arctic Sea Ice Extents, as did this past winter. These Extreme Snows and Rains will continue until it snows enough to increase Albedo of earth to the point it cools and the Arctic Water again freezes. The past ten thousand years had many warm times as warm as now and some warmer than now. Ever warm time was followed by a cooler time. This warm time will be followed by a cooler time.

      • The trend for the past ten thousand years is toward more snow accumulation. I believe that is because the ice is compressed over time. That is even more seen in the Antarctic data because it is much older.

      • Dear Dr. Curry:

        It is simple if we think of of snow melt and permafrost thaw occur as result of water vapor condensation, for the observed positive river runoffs can only occur as a result of water vapor latent heat of condensation, not surface temperature rise. Surface temperature rise is in the order of 0.0000002 degrees centigrade per hour, and all heat transfer equations available to us will show that snow cannot melt due to surface or air temperature rise.

        River runoffs are positive in Siberian watersheds where there are no changes in urbanization, land use/cover, or dam construction. Please refer to Article-7, global warming in the Siberian watersheds posted on my website http://www.global-heat.net. You will find that, the mathematical link between river runoffs and the rise in the concentration of carbon dioxide in the atmosphere is undisputed. This is true for all rivers that experience snow or permafrost accumulation in their watersheds.

      • Judith,

        If you assume that the climate is warming (for whatever reason)

        Disregarding the reason for warming, I would expect to see, after accounting for other factors, a commensurate increase in precipitation at the warmest times of the year and/or the warmest places on the planet.

  7. This is simply another in the list of AGW predictions that has failed to materialize. Since the predictions were based on assertions of understanding the role of CO2 in the atmosphere, it is correct to question other predictions about the role of CO2 in the atmosphere.
    The scientists claiming to study the climate should focus on where the data leads, instead of trying to squeeze the data until the desired conclusion supported.

  8. But Gabi Hegerl (oops, remember her from the recent Nic Lewis IPCC error thread?) has a recent paper in Nature (oops, remember their recent skeptic-bashing editorial?) using computer models (oops…) that shows increased flooding because of global warming, so it must be true.

  9. Judith
    Re: “So what is wrong with the picture that Kevin Trenberth (and others) have been painting (besides the fact that they don’t seem to have looked at actual flood data)? ”

    From a quick search on Villarini‘s presentation, I found no reference to either
    “Solar” or “Hale” or “Hurst” or “Kolgomorov”.

    May I suggest two missing issues are the lack of any analysis relating to 1) the Hale solar cycle or to 2) persistence and Hurst-Kolmogorov statistics. See extensive evidence from Southern Africa by WJR Alexander et al. showing statistical correlation between runoff and the (~21 year) Hale solar cycle. Alexander et al. (2007) Linkages between solar activity, climate predictability and water resource development. (Alexander is providing his exhaustive runoff collection on CD to researchers including a “474-page technical report entitled Climate change and its consequences – an African perspective (Alexander 2006) with 51 tables, 33 figures and 218 references.”)
    See also numerous studies on Hurst-Kolmogorov statistics..
    See especially extensive work by D. Koutsoyiannis at ITIA. e.g. Orbital climate theory and Hurst-Kolmogorov dynamics

    • David,
      I am confused. Villarini etal say that they are NOT SEEING any AGW signals in precipitation ( if i read them correctly, ” in both avarages and extreme events”). What has that got to do with solar cycles? what has that got to with any LTP? they have not seen any signal in 75 years, in an area of about 1-1.5 million sq miles. May be it can be seen when you look at more wider, varied area. may be it will show up in the next 75 years.

      The point is Villarini etal are not seeing any signal in precipitation, TILL NOW. Trenberth and other CAGW folks are claiming all kinds of things based on some irrelevent ( eg. flooding ) facts. That, I believe, is the point of Judith’s post

      • jothi85– I agree, but will add that Trenberth also uses his fear of the potential higher rainfall as justification to reduce CO2 emissions……which I am not sure I see the link to. If CO2 emissions were reduced it would impact rainfall when and where exactly?

      • jothi85
        Thanks for your query. I am not saying there are/not AGW signals in precipitation. What I was trying to point out was that WJR Alexander found significant (95%) correlation with runoff in Southern Africa with the 21 year Hale Cycle. Thus part of the variability in precipitation in other regions may be found to also be linked with the Hale cycle. Consequently some portion of attributions to AGW (if there is any) may on further analysis actually be found to link to the Hale cycle. Pielke Sr. has a 2010 guest post by WJR Alexander http://pielkeclimatesci.wordpress.com/2010/05/20/climate-change-the-west-vs-the-rest-by-will-alexander/>Climate Change: The West vs The Rest by Will Alexander Note especially:

        “Table 10. Comparison of sudden changes in the annual flows in the Vaal River with corresponding sudden changes in sunspot numbers”
        Three-year totals of flows in Vaal River (% of record mean)
        “Three previous years Three subsequent years”
        Average 180 vs 478
        Compare:
        “Three-year totals associated with the corresponding sunspot minimum”
        “Three lowest years Three subsequent years”
        Average 52 vs 300

        I’m not a statistician, but that looks significant to me!

        See also Loehle & Scafetta (2011) modeling global temperatures as long term rising trend, a 20 year cycle, a 60 year cycle plus trend from anthropogenic portion.
        i.e., the 21 year Hale cycle that WJR Alexander finds in runoff, may prove to be the same as the 20 year cycle of Loehle & Scafetta (2011) in temperature. That would be a great project for those groups or others to test.
        See also Ed Fix’s solar cycle model linked to planetary oscillations around the barycenter. This may account for variations in cycle length around the Hale cycle average.

        So I am trying to point to other known or modeled factors that may improve understanding of the runoff and the portions of natural vs AGW – rather than just raising a Chicken Little alarm of catastrophic AGW.

        Furthermore, agriculture is constrained both by CO2 and by H2O availavbility. Increasing both CO2 and H2O has been increasing agricultural yields. The (default) Null Hypothesis suggests further increases in yields with rising CO2 and H2O. Developing countries are critically dependent on increasing agricultural yields to support growing populations. They should thus be strongly supportive of rising CO2 and H2O to benefit their farmers – despite the AGW alarms.
        See: CO2Science.org; under Agriculture e.g., Feeding The World etc.
        See also review Climate Change Reconsidered, especially Appendix 2 Table 7.1.1 – Plant Dry Weight (Biomass) Responses to Atmospheric CO2 Enrichment

    • Note that WJR Alexander et al. find the 21 year Hale solar cycle in precipitation and runoff, but NOT in open surface evaporation. e.g. see data: So Africa trends in evaporation

  10. Trenberth does not do data analysis. Here are the results of my trend analysis for the Atlantic, Pacific and Indian oceans 1948-2010:

    Source: ESRL-NOAA.

    Indian: PW (precipitable water): y = -0.0197x + 42.022
    R² = 0.1804
    Annual Mean Temperature = 0.0172x + 25.318
    R² = 0.6379

    Atlantic PW: y = -0.0331x + 31.164
    R² = 0.2974
    Annual Mean Temperature: = 0.017x + 23.371
    R² = 0.6852

    Pacific
    PW:
    y = -0.0338x + 42.645
    R² = 0.3553
    Annual Mean temperature:
    y = 0.0095x + 25.951
    R² = 0.4265

    Evidently there is no support whatsoever in the above for the claim by the AGW fraternity (Trenberth 2011 passim) that rising temperatures increase the atmospheric concentration of water vapour and thereby the “enhanced” feedback on the greenhouse effect.

    Who needs data when you have faith?

  11. Kevin Trenberth states “The environment in which all storms form has changed owing to human activities. Global warming has increased temperatures and directly related to that is an increase in the water-holding of the atmosphere.”

    When Trenberth starts off with a wrong assumption, that CAGW is real and is happening, then anything he concludes from this ought to be regarded with deep suspicion.

    So when Judith Curry states ” So what is wrong with the picture that Kevin Trenberth (and others) have been painting (besides the fact that they don’t seem to have looked at actual flood data)? “, it is not surprising that she mistrusts what Kevin is saying.

    But there is much more to these two simple statements. Trenberth basically claims he is right for two reasons. First, that the output of the non-validated models proves conclusively that the science is settled and CAGW is real. Second, that there is a consensus among all scientists who know what they are talking about that this is true. This includes the Royal Society, etc.etc. Anyone who dares to commit heresy by producing ideas, data, etc that tend to show that CAGW is wrong, are charlatans, or worse.

    You, Judith, will go so far as to support the idea that Trenberth might just be wrong. What I am waiting for is you to be absolutely outraged at his attitude.

    • Your post is very on point.

      “What I am waiting for is you to be absolutely outraged at his attitude.”

      I’ve watched the blog and board for some time. I suspect there is outrage inside the consensus tribe but being in the tribe trumps behavior you might expect if you were detatched from direct roles inside the consensus as most of the skeptics and board participant are.

      So I can’t explain this pattern either other than ask what would happen if Dr. declared that uncertainty was conclusive and the IPCC and consensus claim (carefully crafted implications regarding co2) that is the core of the agenda is false and based on years of observation politically motivated? If the Christmas card list is much smaller than before 2006 it woiuld likely be even smaller. Her subscription to the New York Times would be forcibly cancelled and so on. Her role in the luke warm function of “communicator” would end, she would be a holocaust denier like many of us are labeled. Given her high profile she would get death threats and all the rest.

      I’m not saying this is why she postures as she does. Dr. Curry does have a knack for many keen skeptics observations only to add paradoxical conclusions to a topic or statement summary. Then again, how did someone stay on the inside of the consensus until 2006 without defending skeptics? There is nothing new about this academic bloodbath and while ar4 was a peak of sorts, regardless of how strongly she might has supported the consensus science view then or now, how did she rationalize the attacks on science dissent prior to coming out and comunicating?

      There is a left-wing overwrite to the eco-green culture and agw consensus, the IPCC and its goals were clearly part of it. Likely she has sympathy for the movement but it would be progress if she admitted this. When we get to this level of honesty the discussion would improve. It can’t be easy I realize.

      • cwon14 writes “When we get to this level of honesty the discussion would improve. It can’t be easy I realize.”

        You and I are obviously in agreement. What I hope someone like Dr. Curry will realize, is that CAGW is simply just plain wrong. That being said, anyone who strongly supports CAGW will have to agree to this eventually. The person who breaks ranks first will be taking an enormous risk, and will be demonized by the remaining members of the “tribe”. But the benefits of being the first to jump should bring enormous kudos and benefits in the long run.

      • What I should have finished up with is the famous quote from Benjamin Franklin “We must all hang together, or assuredly we shall all hang separately.”

      • Jim, you can’t do the right thing for a selfish reward of “benefit”. She has already been demonized inside the hard fringe but those are the minions large in number as they may be.

        The science of climate will always be vague given the tools and knowledge likely in out lifetime. I don’t even doubt c02 might be a measurable climate a input but common sense regarding the scale of others inputs like clouds, oceans the sun and so on just outweigh the carbon cycle or human contributions that less than 5% of the total co2. If you go to another basic flaw that the co2 sink isn’t understood all that well and that none of this could have advanced instead to two key warmist fallacies are accepted;

        A. co2 by humans is compounded while natural co2 removed from discussion. It isn’t just flawed science thinking it was a contrived requirement and I don’t know how this is seldom debated. As if we might be breathing co2 from a coal plant in the 1930′s? If the sink wasn’t expandable it would have taken only one surge in natural co2 to realize the very horror alarmists feared millions of years ago. Of many contortions of logic this one is classic.

        B. Climate equalibrium, another sad joke that is must have in co2 fear. When you accept that the climate is always changing and that inputs change in importance now you a chaos situation on predictions. The sun, oceans and “if we must” co2 might all score different values of climate on different day. That would never do when you’re trying prove something like agw so the fallacy of climate equalibrium was invented and smart people all over the world went along with it. A “good German” scenario is there ever was one.

        Both are jump the shark in scale and these are just the greatest hits for me. This kind of thing goes on all the time on micro topics as well. But enough of the techincal details.

        Has Dr. Curry ever commented on the relative weighting of the political consensus of those at the core of the agw science class and the IPCC? Even the Washington Press core gets polled and disclosed. It might embarrassing but are we suppose to pretend that this science enclave inparticular or eco-science in general isn’t attractive to particular political segment? We’re talking about honest discussion? Perhap Dr. Curry can tell us the University of Colorado in Boulder is a hot bed of conservative academic life? Would that make any sense? It must hurt but given the stakes people should disclose their politcal center of gravity and be honest about their peers. This hasn’t happened even though the informed and media allies understand
        it completely. Kerry Emanual would be appauled to think his objectivity was impacted by his global outlook. Most people in climate are objective and moderate the story goes, the NY Times op ed board would make the same claim. It’s a joke but Dr. Curry plays the same game. Scientists shouldn’t have to be treated like a partisan Washington Press core, they are qualified to a point where you can’t ask. The same defense goes on all through Ivy League campuses and academia in general. All this while they are producing research to steer an entire society at times. AGW consensus is too evolved to play this game of the honest broker.

        http://www.denverpost.com/news/ci_9244192?source=pkg

        It’s a scream of course; one of my favorite lines;

        “Mr. Peterson said it’s not imperative that the new professor of conservative thought be an actual conservative. ”

        Maybe the IPCC can appoint its own “Chair of Skeptic Thought”? No requirement that they be a skeptic of course.

      • well the reason you are wrong is that you are overlooking that CO2 is the largest known climate forcing, by a short mile. Business as usual means applying a 5wm-2+ forcing to the climate from human greenhouse gases emissions.

        You say “common sense regarding the scale of others inputs like clouds, oceans the sun and so on just outweigh the carbon cycle or human contributions that less than 5% of the total co2″

        But they don’t. In order to dwarf the greenhouse 5wm-2 forcing you would need something much bigger, like a 10wm-2 forcing right? Well where you gonna get that from? It’s infeasible. None of the things you mention will cut it and lets be fair you have to speculate not only on the magnitude but also on the sign of the forcing.

      • lolwot writes “Business as usual means applying a 5wm-2+ forcing to the climate from human greenhouse gases emissions.”

        Maybe so, maybe not. However, the problem is that no-one has any idea how much difference a change of X wm-2 makes to global surface temperatures; whatever the value of X is. I am not sure where you get your 5 from. I thought doubling CO2 gave a change in radiative forcing of 3.7 wm-2. And we have not doubled CO2 yet.

        The problem with only looking at radiation terms, is that the bulk of the energy is transferred through the atmosphere by conduction, convection, and the latent heat of water. So I disregard any estimations that ONLY look at radiation terms.

      • I expect we will end up more than doubling CO2. Plus other greenhouse gases. So 5wm-2 is probably an underestimate of what will unfold.

        Why do I think humans will be the dominant climate driver over coming generations? Because unless something provides a higher forcing than that, human greenhouse gases will be the dominant forcing.

        Nothing known other than human greenhouse gas emissions comes close to causing anything as high as a 5wm-2 forcing. And speculation about could-bes is hardly a good justification for assuming human emissions don’t drive climate.

        As for why a 5wm-2 would be enough to drive the climate, well if the climate doesn’t react to a whopping big forcing like 5wm-2, you have to wonder how the climate ever managed to change in the past.

      • lolwot –
        well the reason you are wrong is that you are overlooking that CO2 is the largest known climate forcing, by a short mile.

        That’s an unproven assumption.

        You say “common sense regarding the scale of others inputs like clouds, oceans the sun and so on just outweigh the carbon cycle or human contributions that less than 5% of the total co2″

        But they don’t.

        That’s also an unproven assumption.

        Which makes the rest of your argument ….. unproven.

        Since roughly 50% of the Earth is cloud-covered at any given time, clouds are a bigger factor than you seem willing to believe. But then your belief is irrelevant to reality.

      • Science doesn’t work on proofs. It works on the best explanation to fit the available evidence.

      • Chief Hydrologist

        Science has 3 phases – hypothesis, analysis and synthesis. Analysis can falsify a hypothesis or become a ‘fact’. Synthesis builds disparate ‘facts’ into a coherent theory. But there is no unified theor of climate that a simple solution to emerge.

        Aledo can change the radiative balance by 85 W/m^2 between snowball Earth and the blue-green planet.

        ‘As more experiments are carried out and longer and improved dataseries on cloud cover, cosmic rays, atmospheric water vapour, the amount of atmospheric aerosols, etc. are established, knowledge on cloud cover formation will improve. Until all processes controlling cloud formation are thoroughly understood, any attempt of modelling future climate change may well prove in vain.’ Proffessor Ole Humlum – http://www.climate4you.com/

        Cloud radiative forcing varies considerable over decades – which is all we know of – http://isccp.giss.nasa.gov/zFD/an2020_SWup_toa.gif

      • Then, scientifically speaking, Global Warming is a hoax. No proof necessary.

        Andrew

      • I’m not sure where CH gets his “hypothesis, analysis and synthesis” from. It sounds vaguely Hegelian.

        If anyone is interested in what it is they’d be better reading up on it here:

        http://en.wikipedia.org/wiki/Scientific_method

        Experimental science usually fits neatly into what can be defined as a definitive scientific method, but not all science is strictly experimental in the usual sense. Examples of the latter would include astronomy, palaeontology, geology, etc.

        Its not unusual for Climate change deniers to argue that Climate science isn’t experimental either, apart from one huge unintended experiment, therefore there are no reproducible results, therefore it’s not a proper science etc etc

        If you want to set the bar so high that no-one can possibly get anywhere near it, that’s the line of argument to use.

      • tt –
        Getting your information on anything scientific (or many other subjects) doesn’t tend to give you a lot of credibility. Nor, obviouly, does it give you understanding of what you’re quoting.

      • tt-
        Try again -
        Getting your information on anything scientific (or many other subjects) from Wikipedia doesn’t tend to give you a lot of credibility.

      • Chief Hydrologist

        ‘Scientific researchers propose hypotheses as explanations of phenomena (hypothesis), and design experimental studies (analysis) to test these hypotheses via predictions which can be derived from them. These steps must be repeatable, to guard against mistake or confusion in any particular experimenter. Theories that encompass wider domains of inquiry may bind many independently derived hypotheses together in a coherent, supportive structure (synthesis).’

        The words in brackets are mine – the rest wikipedia. Computer models are not ‘experiments’ in any sense of the term. Climate science consists for the most part in ‘synthesis’ of fragmentary and uncertain analysis using the achaic conceptual model of linear systems.

        All science is experimental as it relies on observation and measurement of the real world – if it doesn’t it is not science.

      • Jim Owen,

        Wikipedia isn’t perfect but if you don’t like it then you can edit it or add to it. I’ve done this myself several times. If you provide proper references then your contribution should stand.

        CH,

        Not all science is experimental. Astronomy, for example, isn’t – its observational, and there is a significant difference between observation and experimentation.

        So any ‘definition’ of what the scientific method should be shouldn’t necessarily include experimentation. Yes it is desirable. It would be quite nice to have a ‘spare Earth’ and time machine with which to experiment. We could double the CO2 concentration and go forward in time in decadal steps and plot out just how much warming there was.

        But sometimes you just have to do the best you can with what you’ve got. The undeniable fact that everything is just not possible does have to be incorporated into the scientific method. Otherwise we end up saying that Climate science isn’t real science – but I’m sure no-one is really saying that are they? :-)

      • “In order to dwarf the greenhouse 5wm-2 forcing you would need something much bigger, like a 10wm-2 forcing right? Well where you gonna get that from? It’s infeasible.”

        Easily done by clouds alone. The Greenhouse (d)Effect is exact 0Wm².

        http://principia-scientific.org/pso/publications/The_Model_Atmosphere.pdf

      • Hank Zentgraf

        I have lived in Boulder for 40 years and know many professors current and retired. All nice people but mostly far left liberals. When Ward Churchill, an extreme liberal at the University of Colorado, came under investigation for research fraud and plagiarism, 399 professors took out a full page add in the Boulder Daily Camera in support of Professor Churchill despite the overwhelming evidence. I knew many of the signers. The city liberal politics are greatly influenced by university faculty and scientists from NOAA, NCAR, and NIST . However I have great admiration for Roger Pielkie Sr and Roger Pielkie Jr. They seem to rise above politics.

      • Professor Curry taught there. She is vilified at Think Progress and by many in the left. She talks tribes but what tribe is she culturally more associated? She contributed to Obama, did she know the climate policy stakes at the time? or Was Climate Policy just a secondary position (that would be ironic) to her? (Peggy Noonan voted for Obama as well).

        How can you talk about being “open minded”, IPCC reform, tribes and not explain that she voted for the same tribes that now denounce her in 2008??
        She doesn’t have to explain but it does seem a paradox.

        Hank I put the Boulder story up because I too have been there, it isn’t hard to grasp the culture. It’s pretty common knowledge even if you haven’t been there and I don’t think most on the left would “deny” the macro stereotype of the self-identity community. Try getting the MSM or the “Consensus” to own up to the general culture (political slant) of the IPCC/Consensus and so on? Because the enclave was small and academic the talking point of it “being all about science” was closely guarded for a very longtime even if many knew this was false even 25 years ago. As it esculated toward policy the wheels have come off the public cover for many but the core of the IPCC members and their center of political gravity remain obfuscated (to enhance their overall impact in the agw movement). So I’d like her comments because she is a contradiction but also getting to honesty would help stop a terrible abuse that is co2 mitigation that would and has done great harm to the world and science.

        Can we pick and choose what we will be honest about and still be considered honest? The political culture of the group around both the IPCC and the Consensus advocaters was and is very important. She doesn’t have to name names but to pretend this is an abstract academic debate like Cope and Marsh in the “Bone Wars” of the 19th century is pathetic. The tactic has been to label “deniers” right-wing while the consensus apolitical and increasingly victims. Again a pathetic portrayal and one she could easily help balance since she was there. Talking about tribes just isn’t enough, tell the narrative about who is about what.

      • cwon14,
        The most extreme of either end of the spectrum is convinced their side is right by rights.
        The lefties, who dominate American public space at this time, have many who are convinced that not only are they right, but those who disagree are either evil or inferior. No room for just wrong, and little tolerance for tolerance.

      • How is it that real science could break down on party lines?

        From JC 9/2010;

        “These labels are terms that reflect a postnormal environment, they don’t have anything to do with science. I’ve used the labels myself in discourse, trying to understand and explain the dynamic of what is going on, and I keep changing labels as I struggle to make sense of the dynamic and not offend (pretty much everyone is offended by their label except for the lukewarmers). In the past I’ve even self-labeled myself at various times as “warmist” or “lukewarmer”, when it seemed that some sort of label was necessary for the dialogue. But no longer. I am through with these labels, and I hope to convince you to be finished with them also. Not only do these labels have nothing to do with science, but the labels are polarizing and are used to denigrate opposing “tribes” that have emerged in this postnormal environment.”

        If labels have nothing to do with science how can you explain the tendency of the debate to be broken down on party lines? If you look at the split “scientifically” how can this input be ignored? Dr. Curry should support probity and the political outlook of any enclave and participant that claims objectivity should be open transparent. The Rubicon was crossed long ago, skeptics are labeled as anti-science while the consensus has purged skeptical dissent from its ranks. Do you really think it was only positive self-identification at CU Boulder that made it liberal enclave? People outside the tribe were rubbed out professionally over decades. The same thing happened at the IPCC and they started from a slanted base from the beginning. Who tends to be attracted to green related fields when we consider a political filter? Who is attracted to the U.N. and global regulatory rationalization?

        I understand the desire for open doors but it’s obfuscation or worse not discuss your general political outlook and worse if you don’t know (or wish to tell is the truth) what a groups culture might be associated with. The crony culture of climate science is plain for some to see but those who have been on the inside like Dr. Curry should come clean. Climate science and the consensus are “post normal”, she has it backwards.

    • You might have a long wait.

      Judith couldn’t be “absolutely outraged at [KT]‘s attitude” without being “absolutely outraged at [her own]‘ attitude”.

      What KT, and others, are reporting about flood intensity and frequency isn’t too much different, in principle, to what Judith herself has reported on hurricane intensities and frequencies.

      http://curry.eas.gatech.edu/climate/pdf/testimony-curry.pdf

      • tempterrain writes “You might have a long wait. ”

        Maybe not. The reference you gave from Dr. Curry’s writing is dated 2006, many years before Climate Etc started. I am hoping that Judith will, in fact, be outraged with some of the things she wrote many years ago. We all of us learn from our experiences with life, and I am sure Dr. Curry is no exception.

      • “Are you taking a career risk?
        A couple of people think so, but I’m senior enough and well-established enough that it doesn’t matter. I also live in Georgia, which is a hotbed of skeptics. The things I’m saying play well in Georgia. They don’t play very well with a lot of my colleagues in the climate field.”

        http://discovermagazine.com/2010/apr/10-it.s-gettin-hot-in-here-big-battle-over-climate-science/article_view?b_start:int=1&-C=

        Jim,

        I’ve watched some of the clips, read other writings. The middle thing is pretty cold and consider the ratrionalizing here. If you’re not “pretty senior” you had better keep your mouth shut as far as your career might go. It’s honest but clearly she looks right at it all the time, figures out many things that effect skeptics are upset about but her identity is from inside the group as a rule.

        “Is it fair to say that the kind of open inquiry you are calling for isn’t being done because scientists have been trying to convey a focused message to the public?”

        That’s part of it. You heard that in the [hacked] e-mails: Let’s simplify the story for the IPCC. But that’s just not how science is. The scientists have gotten caught in these wars with the media and the skeptics. They spend so much energy trying to put them down, energy that isn’t going into uncertainty analysis and considering competing views. I don’t think the scientists have personal political agendas. I think it’s more hubris and professional ego.”

        Jim, do you think hubris and ego (they certainly exist in this or any field) are the core?

        Don’t think scientists have personal political agendas??!!!

        I’ll ask the aliens that are holding me hostage to return me to earth at this point. How far in a bubble can a comment like this come from? tempterrain might be right for all the wrong reasons of course. Dr. Curry is nuanced, perhaps torn but is still a card holder of the establishment. Of course the tv interviews on the site are from Canada with a left-wing media filter and all warmists of different types splitting hairs from the same general outlook.

        This isn’t a person on the road to Damascus. She isn’t leaving the consensus even she annoys them. It’s complicated but she isn’t owning up for many things and in a very calculated way.

  12. Dr. Curry, it seems to me that Trenberth is confounding his assumptions. One of the assumptions is that of psuedo equilibrium in the formulation of the starting of GCM’s. Another assumption is that as temperature increases the air carries more water. Rain can be veiwed as a transient accumulation phenomena, such that due to relative humidity changes from water vapor or temperature changes precipitation changes in response. It would seem that Trenberth in pointing out the assumption that over oceans that water is not an issue, and IIRC, that it is expected that over land temperatures in response to increased energy not expressed as enthalpy from water vapor, that the temperature increases, for Trenberth to be correct he needs to more explain in more detail why. If we increase temperature and increase water, then one of the possible solutions is that the amount of rain or even storms stays a constant. The results to date indicate as such. Considering the state of data, I would agree that perhaps we do not have enough enthalpy data throughout the atmosphere to anser the question, but that makes Trenberth speculative versus Villarina and Smith’s results.

  13. Scientist uses online forum to talk anecdotes without looking at actual data. What could possibly be wrong with that?

    ps you call this a technical thread? Sounds more like parody to me

  14. It’s been 20 years since I took college chemistry. But I do remember the concept of vapor pressure.

    There is a significant problem that the climate science clique faces with the general public – if increased temperatures mean more rain, why isn’t the Mojave desert a lake in the summer? Why does Fresno have a temperature of 106 and a dew point of 34?

    The general population deals with this stuff every day. We all know that warmer air CAN hold more moisture. We also know that “CAN hold more moisture” is entirely different from “IS holding more moisture.” People can look at the hot and parched Mojave desert summer air and compare it with the very cold and moisture laden Buffalo, NY winter air when the winds are blowing off Lake Erie. How does a person believe the explanations when our experiences show that it just doesn’t make sense? I have ZERO doubt that Trenberth and the others know of vapor pressure gradients. So why aren’t they discussing the variables like vapor pressure gradients, temperature gradients, etc, that actually cause more moisture in the air?

    The only answer I can think of is that Trenberth and his ilk have too much to lose.

  15. So what is wrong with the picture that Kevin Trenberth (and others) have been painting (besides the fact that they don’t seem to have looked at actual flood data)?

    Quite simply, argument rises from theory rather than directly from relevant data. The theory very well may be evidence-based and have validity, but is a step removed from the question at hand. As such it allows for unrecognized (ignored?) assumptions that reduce its ability to predict accurately. At best, postulating that warm moist air increases flooding might support the data rather than lead it. Going even farther in claiming that human activity is mostly responsible for creating the warm moist air pushes the argument farther out on the limb of uncertainty. The picture is wrong because it was painted from memory in a studio rather than photographed on site.

  16. A couple of points:
    Trenberth makes several definitive statements that do not seem fully supportable
    1. He states that sea surface temperatures have risen by 1C since 1970 which I do not believe to be an accurate statement
    2. He states that humidity over the oceans has risen by 4% which I also question how he determined accurately

    His comments that humans have changed the environment are undoubtedly true, but meaningless without a qualifying statement of how much.

    Overall on the point of the potential for increased flooding…..the situation calls for countries around the world to protect their citizens by construction of proper infrastructure to protect people from both flooding and potential drought conditions. The United States should look after itself in this regard as should all other nations. If some nations are to short sighted, or to corrupt to build infrastructure that is their own problem and not the problem of the American taxpayer.

  17. Tomas Milanovic

    Interesting papers.
    Humidity is one point and precipitation another.
    And averages are all but misleading.
    If the “average” humidity went from 25% to 28% at a specific location (f.ex because of a local temperature augmentation) , there would be absolutely no reason why the precipitation at that same place should increase.
    The only constraint on precipitation is that total precipitation ~ total evaporation with the difference being the change of atmospheric water content. Of course the latter being unknown, there is a huge space for transitories (on a year scale) which can and do translate in local spatial anomalies of evaporation and/or precipitation.

    Now as this paper rightly shows the leading role for extremal phenomena (floods/droughts) is played by spatial features of the region considered and not by some quantities averaged over decadal time scales (aka climate).
    There is à priori no compelling physical reason why an increase of temperature should translate in an increase of precipitation and even less in an increase of “extreme precipitation”.

    It’s like the question of spatio-temporal oceanic oscillations and cloudiness.
    Of course all questions about which causes which are vain because they are both just 2 different interacting degrees of freedom within the spatio-temporal chaotic system.
    So all combinations may exist – one increases the other decreases , one increases the other increases etc.
    The problem of precipitation, along with the one of cloudiness are the most complex because to the relatively understood problem of the time lag adds a largely non understood problem of the space lag.
    E.g when 2 things happen not only at different times bu also at different places, it gives a very complex dynamics.

    That’s why I am convinced that only local considerations (like these papers) or full spatio-temporal dynamics for the whole system can have a chance to lead to real progress.
    It has been for years that I don’t read anymore papers using just this 19th century paradigme about “equilibriums” (which are not) and “global averagings” (which are meaningless).

    It should be about time that people realize that the only thing that can be predicted for a spatio-temporally chaotic system are probabilities that depend on the spatial coordinates and even that is a pious hope that the system be so kind and behave ergodically.

  18. Dr. Trenbeth has often maintained that there has been a documented increase of ~4% water vapor, but I haven’t heard of him providing a citation for said evidence. When I looked at the specific humidity data from NCEP’s CAR reanalysis (up to 2007), I came up with an increase of approximately 2%. Above TRC Curtin provides ocean specific trends that also don’t support Trenbeth’s contention. Dr. Curry (or anyone else), do you know what data supports Trenbeth’s contention that water vapor has increased by 4%? As noted above by Jerry, just because warmer air can hold more water doesn’t mean that it necessarily does hold more water.

    Villarini’s analysis seems compelling for the regions studied and seems to be a much more realistic approach than some of the other approaches that use satillette data to estimate precipitation and runoff.

  19. As you point out Judith, the hypothesized link between warming and increased flooding stems from the reasoning, based on the Clausius-Clapeyron equation, that warming will lead to an enhancement or acceleration of the hydrological cycle. Notably, Trenberth, Karl, Groisman, and others have also argued that the observed increases in precipitation over the past century, which have been documented as occurring disproportionately in the upper tail of the distribution (i.e., “heavy and extreme” precipitation) must, therefore, be manifesting itself in increases in peak streamflow. Over the past decade, a number of hydrologists at the USGS, the agency responsible for gauging the nation’s streams, have analyzed trends in daily streamflow across the country. They have uniformly used records from stations minimally affected by such confounding human activities as regulation and diversions, so as to reflect primarily a climate signal, and have also investigated changes in the entire distribution of flows from the annual minimum to the annual maximum. So they have been able to assess where in the distribution of streamflows trends have been occurring.

    Their results, and those of other hydrologists outside USGS, have been consistent and very telling. All have found increases in flow over the past century, in agreement with increases in precipitation. However, those increases have been occurring in the low to moderate range of flows, from the annual minimum through the annual median. More significantly, very few stations have experienced trends in annual maximum flow and, among those that have, there have been as many decreasing trends as increasing. Thus, it appears that the observed increases in what has been termed heavy and extreme precipitation, i.e., defined by Karl et al. in their 1995 Nature paper as >50mm day, has been sufficient to increase low to average streamflow, but not sufficient to increase peak streamflow.

    To understand this association better, USGS also evaluated the seasonality of the trends. Most studies of precipitation trends have indicated that the increases are occurring primarily in autumn and early winter. Across the U.S., early autumn is the season when streamflows are at their annual minimum, with moderate flows typically occurring in late autumn to early winter. So the observed increase in precipitation, even in the heavy and extreme category, is occurring at the time of annual minimum streamflow. Thus, at least to date, the nation has benefited from having more water coursing through its rivers and streams, and has not had to pay a flood penalty for it.

    In all likelihood, the apparent conundrum between increasing “extreme” precipitation and the lack of increasing floods can be traced to the commonly used definition of “extreme” precipitation. A 50mm per day event is not a flood generator unless a basin is already at saturation. Most significant flooding in the U.S. occurs in response to multiday rainfall episodes or after weeks or months of persistent rainfall. Perhaps a 50mm per day rainfall threshold has some significance in terms of meteorological extremes but, in terms of flood hydrometeorology and hydroclimatology, it is does not.

    For more details on this issue see: Lins and Slack, GRL, 1999; Lins and Slack, Phys. Geog., 2005; McCabe and Wolock, GRL, 2002; Small et al., GRL, 2006.

    • HFL, thanks very much for this analysis

    • An increase in river flow does not have to indicate increased precipitation. Groundwater mining must be taken into account.

      • That’s true, but the data used in nearly all of the U.S streamflow trend studies come from stations in the USGS Hydro-Climatic Data Network (HCDN). The criteria for stations to be designated as HCDN included:
        1. Long records; i.e. >20 years and preferably >50 years;
        2. Data with an accuracy rating of at least “Good”;
        3. Minimal anthropogenic effects in basin, including minimal regulation
        of the stream discharge, or reduction of base flow due to extreme
        ground-water pumping.
        So the results of studies using data from the HCDN should be primarily reflective of prevailing climatic conditions.

      • Perhaps it indicates precipitation but then it must be reconciled with other data that shows no increase in precipitation such as the one I linked at the top and this study which states no increase in precipitation but an increase in severe precipitation

        “There is no discernible trend in average precipitation since 1951, in contrast to trends observed in
        extreme precipitation events (CCSP, 2008).”

        http://downloads.climatescience.gov/sap/sap1-3/sap1-3-final-ch3.pdf

        So it seems opinions on this are as varied as the weather.

      • Except for the thousands of lost long record streamgages.

      • HFL – Thanks for the info on the HCDN. The USGS tends to pretty good work so their findings are certainly interesting and relevent. However, while they certainly screened the gaging stations to minimize the effects of land use changes, development, etc as well as flow regulation that doesn’t mean there arent’ any non-climatic anthropogenic or regulatory effects on many of the locations. I took a quick look at many of the locations in the mid-Atlantic and northeastern states that are in the HCDN and for all but the smallest basins, there certainly would be non-climatic anthropogenic influences that effect trends in streamflow. In larger basins in these states, it would be almost impossible to not have such effects. For example, I am extremely familiar with the Delaware River Basin from doing a number of environmental studies in the area. One of the HCDN gaging stations is the Trenton gaging station on the main stem of the Delaware near tidewater. Compared to other major river basins in the northeast, the Delaware and its tributaries have few dams and minimal flow regulation. It does show a slight (~4%) , and probably statistically significant, increase in average daily flow over the past century. However, there has been an enormous amount of land use change in the basin as well as some regulatory increases of minimal allowable flow. It would take a great deal of effort and it may not even be possible to determine if this slight increase in flow is due to climatic changes or non-climatic anthropogenic changes.

        I think you make a very valid point in bringing this information up, but depending on the region of the US, it may or may not be as reflective of climatic changes as suggested above.

      • Dear Steven,

        Indeed, river runoffs are positive in spite of the fact that precipitation is decreasing over much of the land, contrary to the conventional wisdom. This due to the rise in the concentration of carbon dioxide in the atmosphere. For more, please see the supporting mathematics in Article-7, global warming in the Siberian watersheds posted on my website: http://www.global-heat.net.

    • Interesting USGS document.

      The dying of the thermometers has a dying of the streamgage counterpart. 1000s shutdown in the last 30 years.

      “Looking at the Pacific Northwest for example.
      At the end of 1979 we had 317 streamgages operating which started in 1930 or before.
      Today, we have 220 of those still operating. A loss of 97 (31%).”

      “San Pedro River at Charleston, AZ 1913-2002, trends in streamflow
      Primary driver is ground-water drawdown”

      “Flow timing shifts in areas where snow has been significant”

      More snow = more flow? I thought snow was a thing of the past!

      http://www.epa.gov/nrmrl/wswrd/wq/wrap/pdf/workshop/A3_Hirsch.pdf

    • Dear HFL,
      With all due respect, your analysis cannot be right for precipitation has been decreasing over much of the land. There is a large number of papers on this subject. Just make sure that the authors or institutions behind the publications are not ‘contaminated” by the politics of climate science. Here is a partial list from around the world:

      1) Calabria daily rainfall from 1970 to 2006, S. Federico et al, Natural Hazard and Earth Sciences;

      2) Compatibility analysis of precipitation and runoff trends over the large Siberian Watersheds, Svetlana Berezovskaya et al, Geophysical Research Letter vol 31, L21502

      3) A tree-Ring reconstruction of past precipitation for Baja, California sur, Mexico, Sara C. Diaz, et al, International Journal of Climatology

      4) Study of the rain intensity in Athens and Thessaloniki, Greece, C.M. Philandras et al, Advances in Geosciences.

      If you search the web, they are available for free. If you cannot find them, please contact me through my website and I will e-mail them to you. Sorry I was unable to copy their links.

      • Again the same statement “over much of the land” is written. Sorry but your analysis is useless without better data.

      • Dear Bob,
        Over much of the land, because we do not have data that covers all of the land. For the ocean, we have virtually nothing at this time.

      • Nabil

        Over the land, how were the sites where measurements were taken selected? What was the measure method? Who did the study? How many total sites were selected and how many showed lesser vs greater rainfall? etc etc etc

      • Dear Rob,
        I’m sorry that I have to copy most of the reply to this comment fro a previous one.

        I operated a weather station and the present reduction of about 0.8 mm annually can be measured easily, if attention is paid. In the last 50 years, average precipitation reduction has been about 0.5 mm annually, which can be measured as well. It is easy to spot precipitation trend in area where precipitation is small say 250 mm annually or less. It will be harder to spot a trend in precipitation say in India, Philippines, Louisiana, England, or Illinois, where annual rainfall is in meters.

        If you refer to the authors of the papers, I see no reason why you should question their ability to to analyze precipitation. I think graduated from universities in Italy, Greece, Mexico, or other parts of the world are qualified to analyze precipitation trend. They are not a coincidental one or two publications, but a large number of them that show a reduction in precipitation with time, and we should pay attention to their findings.

      • I’d find this more persuasive if I didn’t know that Illinois and England do not, on average, receive precipitation “measured in meters”. Annual rainfall at Chicago in about 96 cm. Annual rainfall in London is only about 65 cm

        A general average rainfall reduction of 5cm over the 20th century? I’m sorry, that simply doesn’t seem very credible. Even our friends the climate scientists would surely have noticed that. Here’s an example of their take on the situation http://www.giss.nasa.gov/research/briefs/delgenio_02/ AR4 asserts an average increase of 1.1 cm over the century http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch9s9-5-4-2.html

        Let me also draw your attention to the graph of rainfall at Sacramento in icecap.us/images/uploads/Persistence.pdf I picked Sacramento more or less at random because it has long records, a fairly arid climate, and doesn’t have a whole lot of thunderstorms. I don’t think you can really get cm accuracy trends from data like that, much less mm accuracy. I’d note that the trends or the “century” 1850 to 1950 would be quite different for the “century” from 1900 to 2000.

      • UK average is 1125mm for rainfall.

        Slightly above the 1971-2000 average — maybe 25mm.

        Maybe 50mm above 1910. 5%.

        Sunshine Hours are up from 1340 to 1420 from 1929 as well. 6%.

        http://www.metoffice.gov.uk/climate/uk/actualmonthly/

      • Unfortunately AR4 does not talk about sunshine hours. They seem to have completely forgotten sunshine hours can vary …

        How forgetful of them.

      • Dear Don,

        Let us straighten the math. The calculated and observed present reduction in precipitation is about 0.8 millimeters annually. The observed average precipitation reduction in the last 50 years is about 0.5 millimeters annually. The cumulative reduction (or reduction in water reservoirs) is about five centimeters in the last fifty years. Seems small, but it is a lot for arid countries. The notion of steady drought will have psychological effects and will trigger migration.

      • Dear Done K,

        I operated a weather station and you can spot precipitation reduction of 0.5 mm annually with certainity, particularly in arid areas.

  20. Steve Fitzpatrick

    The contrast between Trenberth and Villarini, in both methodology and conclusions, sheds some light on why climate science generates so very much exasperation and resistance from skeptics. Villarini does careful studies using the available data and concludes that there is no observable trend in flooding which can be rationally assigned to warming. Trenberth appears to discount these (and other) data based results and conclude that increased flooding is inevitable, based on his understanding of how Earth’s climate behaves.

    Trenberth’s take on this (and it seems he shares this take with many well known climate scientists) reveals that his faith in his understanding (which is, not coincidentally, also the dominant paradigm in the field) is so great that he will simply discount or ignore any data which conflict with his understanding.

    As Thomas Kuhn noted, this is characteristic of a science that is facing a paradigm shift; defenders of the existing paradigm discount all conflicting data and analyses in order to preserve the integrity of the dominant paradigm. But at some point the contrary evidence is simply too strong to discount, and a shift to a new paradigm takes place. Sadly, it is leading scientists, those who dominate a field, who most strongly defend the current paradigm. Because they are influential, the shift to a new paradigm is delayed; it must often wait for them to either die or retire from active research, so that younger scientists (not so wedded to the dominant paradigm) can adopt a more rational view. History shows that leading scientists almost never accept a new paradigm, even long after it has fully displaced the old one, and so they become largely irrelevant. (Einstein refusing to ever accept quantum mechanics is a good example.)

    Those of us who are young enough can watch the process unfold in climate science over the next decade or two..

    • ian (not the ash)

      Alas Steve, if Chris Colose’s comments are indicative of the ‘understanding’ of the current crop of near graduates I suspect the paradigm shift may be delayed somewhat.

      • Ian – I generally don’t get involved in these discussions about individual participants, but since I happen to know Chris (as a Web colleague, not personally), I thought I’d say something. Chris is very knowledgeable about climate science and climate change, and I have rarely observed him to make an inaccurate statement (although as with everyone else, there are exceptions). Chris is also somewhat hot-headed at times, with an impulse toward exasperation, and that has antagonized some participants, but it doesn’t detract from his understanding of the subject matter. Even those bothered by his commentary could benefit from paying attention to the substantive comments he makes on the science itself.

      • Steve Fitzpatrick

        Fred,
        I don’t mind cutting Chris some slack; he is after all quite a bit younger than my older son, who finished is PhD in molecular biology some time back, and who shows a whole lot more perspective on most all subjects than Chris. Still, someone like Chris would do well to think a bit more before he responds, and to understand that anyone who disagrees with him is not automatically wrong/idiotic/delusional/evil etc. The exuberance of youth is usually tempered by experience; I sure hope, for his sake, that happens with Chris.

      • “I have rarely observed him to make an inaccurate statement”

        Translated: He shares my beliefs.

        Andrew

    • Steve, unfortunately you description of Kuhn’s model of science is not quite correct. First, contrary evidence is ignored at all times, not just when a new paradigm is nigh. Second, the new paradigm only arises once it has actually been formulated. The strength of the evidence against the old paradigm is not sufficient by itself. It is not clear that we have a new paradigm at this point, just a lot of looking.

      Another complication is that Kuhn’s model does not contemplate the present case with AGW, where ideological and political forces far outweigh the scientific debate.

      • Steve Fitzpatrick

        David,
        Yes, the mixing of ideological and political forces with climate science complicates things. If anything, I would say that those factors tend to exaggerate the resistance to a change in paradigm. Now maybe interpretations have changed since I studied Kuhn (in 1972!), but I am pretty sure that an incidence of contrary information, which is resolutely discounted or ignored by the defenders of the dominant paradigm, is indeed an indication of a coming paradigm shift. I could be wrong about this, but I wouldn’t bet on it. As for the new paradigm, I think it has already been formulated: climate sensitivity to radiative forcing is much lower than the IPCC view of ~3C per doubling of CO2; it is probably more like about half that.

      • Steve, by coincidence I too studied Kuhn in 1972! As part of my doctoral dissertation. The basic point is that anomalies are present and ignored from the beginning, not merely on the eve of a new paradigm. Nor is there a new paradigm, alternative to AGW, on hand. Rather we have the interesting case of a relatively well developed hypothesis in AGW versus the concept of natural variability, for which there is a lot of evidence but no specific alternative mechanism.

      • Perhaps we should include The Dancing Wu LI Masters,Zukav, as well; and realize that asking questions not considered is an expression of science as much as gathering data and torturing it to confess.

  21. John Vetterling

    Maybe it is because I am also a civil engineer, but I see this a little differently.

    To me what is significant is that another scientific discipline, civil engineering, has taken the AGW hypothesis at face value, e.g. warming -> greater flooding. We then have tested that hypothesis using the available data and found the hypothesis unsupported.

    If AGW is ever found to be lacking this is how it will happen. Other scientific discipines will examine the hypothesis within their own domains, either finding support or lack of support. Gradually the greater scientific community will reach a true consensus.

    • John,
      This would be the case of the AGW movement had not made for a dysfunctional dialog on climate science.
      The AGW believers are interfering in the review of the hypothesis and pressuring people to either ignore contra-results or to confabulate/fabricate supporting data and results.
      This has pushed out the time frame for rationalizing the review of coliamte science and the AGW view of it.

    • John, by coincidence I am a CE, who worked my way through grad school in Phil Sci as a river regulation engineer. The problem here is that the flow data is so dominated by regulation that failure to confirm AGW does not disconfirm it. Thus the hypothesis is not truly unsupported, because the data is just not natural. Every river in the eastern US is controlled to some degree, most heavily.

  22. Wouldn’t the average amount of rainfall over the world be more related to ocean surface temperatures than air temperatures? The rate of rainfall would have to match the rate of evaporation, which would have more to do with ocean SST, I would think.

  23. The maximum capacity for water vapour equilibrium between water (liquid phase) and vapour (gas phase) is a function of temperature. When temperature increases molecules in both liquid and gas phases have more kinetic energy which makes condensation more difficult and evaporation easier leading to a new equilibrium with a greater proportion of gas phase molecules and therefore a greater water vapour capacity.

    1. Is there empirical evidence which quantifies the additional water vapour evaporated to the atmosphere as a result of an increase in temperature?

    2. Does that increase exceed the increased capacity of water to remain in the gas phase as a result of that same temperature increase?

  24. Vaughan Pratt

    From the conclusions of the first paper (by Villarini and J.A. Smith):

    The abrupt changes in flood peaks can be associated with anthropogenic changes, such as changes in land use/land cover, agricultural practice, and construction of dams. The trend analyses do not suggest an increase in the flood peak distribution due to anthropogenic climate change.

    I don’t understand this statement at all. We have three variables F for flood peaks, A for anthropogenic changes in agricultural practice and construction of dams, and C for anthropogenic changes in climate. To these I’ll add a fourth, D for doubling of world population in the last 40 years. V&S don’t seem to be denying that C is associated with D. Furthermore they assert that F is associated with A, which presumably is also associated with D. Yet they claim no association between F and C.

    On the face of it this would seem a very difficult claim to prove, so it is instructive to examine their reasoning. They consider “abrupt changes in the mean and variance of flood peak distributions through change point analyses and temporal trends in the flood peak records through nonparametric tests”, which they model by the location, scale, and shape parameters of what they call the generalized extreme value (GEV) distribution, and find that “abrupt changes, rather than slowly varying trends, are typically responsible for nonstationarities in annual flood peak records in the eastern United States.” They then argue as follows.

    (i) There is no association between F and C because F and its storms change abruptly whereas C is a slowly varying trend.

    (ii) There is instead an association between F and A.

    A nice argument, yes?

    But A is also a slowly varying trend. (Without D, A would not have the impact it’s been having lately — the population has been doubling every four decades or so over the past century, an exponential rate of growth, but slower than the sudden changes causing storms and floods.)

    If you associate flood peaks with something that is varying slowly, and then turn around and deny any association with something else on the ground that it is varying slowly, that’s not a logical argument.

    At the risk of distracting attention from my main point, I don’t find it terribly surprising to see Pielke quoting from this paper given that Villarini is a recent student of Krajewski who has two coauthored papers with Pielke and several with Villarini including the second of the two papers under discussion here. The majority of the contributors to this blog will find the papers of Pielke, Krajewski, and Villarini very supportive of their position that CO2 is not having a significant impact on the planet. Perhaps it isn’t, and perhaps there are logically sound arguments to show that it isn’t, but the above argument based on rates of change isn’t one of them.

    • Villarini sent me an email saying that he read the post, and also sent me copies of the papers. If anyone wants to take a serious look at this and doesn’t have copies of the papers, send me an email.

      • Vaughan Pratt

        The first paper (the one I was commenting on) is freely available at

        http://www.colorado.edu/geography/geomorph/geog_5241_f10/villarini_10.pdf

        The second is behind a paywall at

        http://onlinelibrary.wiley.com/doi/10.1111/j.1752-1688.2011.00540.x/pdf

        (Stanford has a subscription and I presume Georgia Tech does too.)

        The only relevant difference I could see is that the first is for flooding in the east coast while the second is for the midwest. The logic supporting the claim of no association between flood frequency and climate change is unchanged: CO2 changes slowly, flood peaks and their proximate weather conditions change far more quickly.

        Meanwhile it occurred to me to ask the following. If a mallet swinging back and forth with a frequency of 1 Hz strikes a gong, does it follow that the consequent vibration of the gong cannot exceed 1 Hz?

        The relevance of this question is that if CO2 were to impact the Earth slowly, must it follow that the consequent fluctuations in storms must also be slow?

        Or to take another example better suited to fluids, if you sweep an oar steadily through water, must the vortices it creates behave just as steadily, or could they behave chaotically, with much faster fluctuations than associated with the movement of the oar?

        I don’t see why a steady increase in CO2 could not cause chaotic behavior.

    • Hank Zentgraf

      When I read your post what comes to mind is a sort of “climate resonance” similar to the well established tidal resonance of the Bay of Fundy where tides are sometimes much higher due to a fluid resonance phenomenon.

    • The US flood control program is about half built ( because the greens pretty much stopped it in 1968). Every river in the country is controlled to some degree as far as peak flows are concerned. So the idea that we can measure natural flooding by looking at peak flows is simply wrong. This is their basic conclusion. Human influence dominates the flow. Of course the half built system is still overwhelmed, but not enough to be useful, as it were.

  25. Leonard Weinstein

    The amount of evaporation has to equal the amount of precipitation in the long average. The air temperature does control the immediate amount of water vapor the air can hold (and thus drives the short term evaporation rate), but the long term mechanism that controls the actual average amount of water evaporated is only due to absorbed solar insolation (amount of absorbed sunlight). If there is less solar insolation, evaporation cools the ocean surface, which cools the air, and less water evaporates until a new equilibrium is reached. If there is more solar insolation, the water warms, which warms the air, and the water evaporates more. You have to keep in mind what is actually driving the water and air temperature.

  26. Nabil, I don’t read the http://ine.uaf.edu/werc/people/yang/bcp/2004_berezov_grl.pdf
    paper as stating there has ben a decrease in precipitation. They state the following in the conclusions:

    “Conventional wisdom would suggest that increased
    precipitation would be needed to produce additional runoff.
    An exception to this logic would be the loss of water from
    storage (lakes, glaciers, subsurface, etc.), however this
    would be a transient process with the source eventually
    becoming depleted. Results from this paper direct our
    attention to the quality of the precipitation and runoff data
    and the question, is the quality sufficient to make accurate
    trend predictions or to support the conclusions reached in
    numerous papers on Arctic hydrologic change? We have
    only exposed the question in this paper, not answered it.”

    They had some conflicting trends in precipitation and I think their conclusion was the best one possible.

  27. Dr. Curry – Your statement “An increase in atmospheric water vapor associated with warmer temperatures doesn’t necessarily increase rainfall…” is contradicted by a careful consideration of tropospheric energetics (latent heat transfer), which leads to the expectation that warming does indeed lead to more rainfall. See this paper for a good explanation, and a discussion of oibservations compared to model results.

    • Pat thanks very much for this link

    • Typical AGW beleiver ignores reality in favor of the studies.
      Pat, please explain why the climate science community would rather tell us to ignore the states in favor of ht emodels?

    • Pat–I see nothing in the 2008 two page article you posted that would show that Curry’s conclusion to be incorrect.

      • Hunter – See the references to observations in the cited paper.

        Rob – See the section “Understanding Precipitation Change
        and Its Link to Temperature”.

      • Pat

        I had read that prior to my comment, but I do not see any data to demonstrate that Curry was incorrect. It appears to only be the writer’s opinion or hypothisis based upon what he understands in the GCM he was using or familar with at that time. Are you aware of any “hard data” that would support your conclusion.

      • The argument given in Lambert et al. follows from basic considerations of tropospheric energy transport, irrespective of any particular model. It may be flawed, but not obviously so. Data, such they are, are given in the references (e.g., Wentz et al.).

      • Pat,
        Every metric shows that historical flood rates, levels and extremes are in a typical range.
        Please do not go more circular and simply refer back to a paper that ignores this.
        The interesting metric is that the AGw community has a great tradition of ignoring reality and hyping extremes to promote the idea of catastrophic global warming.
        Why is this an acceptable pattern of behavior from alleged professionals?

      • Hunter – I made no assertions regarding flood rates.

    • Global warming–driven increases in surface and tropospheric temperatures result in increases in tropospheric radiative cooling. To preserve energy balance, latent heating must increase to balance this cooling. Therefore, precipitation increases with global warming

      It seems to me they’re using faulty logic there.

      • Pat

        Perhaps we can agree that the author of the article you posted believes Curry to be incorrect but bases that opinion on other than hard data.

        Regarding what Curry wrote—“An increase in atmospheric water vapor associated with warmer temperatures doesn’t necessarily increase rainfall”—I think her comment will never be shown to be incorrect. The “doesn’t necessarily” is key.

      • Fine.

  28. It seems likely that Villarini and Trenberth are both right, and not in conflict.

    Because an increase in the hydrologic cycle in a warmer climate is expected to enhance both evaporation (drying) and precipitation (wetting) events, the net effect in terms of liquid water balance is difficult to predict and even to ascertain from measurements because they tend to balance out. In fact, the increase in atmospheric humidity is well documented, but that by itself does not tell us what is happening to the rate of addition and subtraction from the atmospheric reservoir. More water in the atmosphere does not necessarily imply that it is cycling faster.

    It is possible, however, to look at what each is doing individually. GRACE-based measurements since 2001 of fluctuations in land and ocean water storage due to precipitation and evaporation have demonstrated what appears to be an acceleration of the Hydrologic Cycle, as indicated by an increase in the amplitude of the fluctuations.

    A much longer series has been studied with a specific focus on precipitation. Min et al examined extreme precipitation trends over the interval 1951-1999 based primarily on Northern Hemisphere land data – Nature 470:378-381, 2011 and found a significant rise during that interval.

    “We compare observed and simulated changes in extreme precipitation based on the annual maxima of daily (RX1D) and five-day consecutive (RX5D) precipitation amounts for the second half of the twentieth century. We chose these indices because they characterize extreme events that often cause impacts on society, and because these annual extremes can be used to estimate the probability of rare events such as 100-year return values, which are used in the design of infrastructure… Observations show overall increasing trends in PI, with 65% and 61% of the total data-covered areas having positive trends for RX1D and RX5D, respectively.”

    Comparison of model simulations with the observed trends showed the modeled anthropogenic component to yield similar values, although the models tended to underestimate the observed rise in extreme precipitation events. Whether this underestimate would apply to future trends remains conjectural.

    It seems likely that globally (or at least in the Northern Hemisphere), precipitation extremes have been increasing, although this need not be matched regionally and would not conflict with regional estimates lacking such a trend. Whether this increase in “extremes” – even 5-day extremes – translates into an increase in significant flooding or “flood peaks” is difficult to assess – perhaps even impossible, due both to different definitions of flooding and the multitude of other factors that affect flood risk on a local level as described by Villarini. It is possible that a continuation of the trend would raise the flood risk, however, even in areas that are not currently vulnerable.

    • First – to correct a typo in my comment above, the GRACE measurements didn’t start until 2002.

      It’s important to distinguish the hydrologic cycle from average precipitation rates. A faster cycle tells us that both evaporation and precipitation are increasing, with perhaps a lag between the two due to accumulating water in the atmosphere. However, the total quantity of water precipitated as rain or snow over an interval is not an accurate measure of how fast the rain or snow is falling when the precipitation is actually occurring. If, for example, evaporation exceeds normal for a month in a particular region, creating a drought, and precipitation then exceeds normal the following month, creating a flood risk, the total rainfall during those two months may have remained unchanged, or deviated in either direction. More importantly, if drought-prone areas experience more evaporation, and flood-prone areas more precipitation, the balance may again remain unchanged, but at the expense of both more floods and droughts – this is what an enhanced hydrologic cycle would predict (although requiring empirical confirmation). For all these reasons, extreme events may be more relevant than long term averages in many regions.

      • John Vetterling

        Odd that Mim et al report a trend of increasing max 1-day and 5-day precip. while Blunden et al find no trend in precip. Granted they are measuring different things, but if the AGW hypothesis is correct, at least Trenberth’s statement of it, then we should expect to see both increasing.

        Also, if 1-day and 5-day max precip is increasing, why is it not reflected in the flood stages

      • John – see my above comment. When both evaporation and precipitation are increasing, the net result of the balance between them may be little change in overall rates of either but an increase in extremes.

      • John Vetterling

        Yes, but then why aren’t those extremes expressed in the flood records. Where did that extra precipitation go?

      • John – I tried to address this above. Flood peaks depend on multiple variables, and are different from one region to the next. Excess precipitation may or may not create a flood depending on conditions, and also on the definition of flooding or flood risk. The excess will create extra runoff, but this may or may not result in an overflow. Also, the Min et al paper refers to the Northern Hemisphere and not to a more limited region. I don’t think there’s a mysterious disparity between the increase in precipitation extremes and more variable data on floods, particularly if the latter is focused on smaller regions. I haven’t seen data on flood peaks over the entire region covered by the data on precipitation extremes, but it might be very “noisy” due to the large multiplicity of variables involved in flood risk beyond precipitation rates.

      • Fred,
        Where does this leave the assertions of the Trenberth faction?
        And what about mitigation?

    • John Vetterling

      I know why Min et al disturbs me.

      They define “extreme” precipitation events as annual maximums. But in hydrology annual max events aren’t even significant. We largely ignore them. Extreme events are 50-year, 100-yr, 500-yr events. Having read their paper they largely ignore these.

      From a statistical basis they should be doing the Bayesian analysis to determine if their results alter the conditional probability of these extreme events, not piddling around with annual maximums.

      • John – They do briefly refer to the 100 year problem. However, I think their focus differs from yours. You may be concerned about the practical challenges posed by severe floods. They address the question as to whether the climate is behaving in terms of precipitation extremes as might be expected from an accelerated hydrologic cycle – something that would be reasonable but not inevitable. It’s possible that the Bayesian analysis might be feasible from their data, even though they haven’t performed it.

  29. How can it be in this thread with 72 messages so far that only now someone like me has to contribute that when Hansen testified before Wirth’s committee in Congress in 1988 stating , the Mississippi was at record LOW levels. People’s and widespread drought was what was feared. Yellowstone was also on fire that summer.

    http://www.worldwatch.org/node/5790

    Come on, people! Science means testing a theory against ALL the data, not just the stuff that supports your argument.

  30. Sherlock Holmes, A Scandal in Bohemia:

    “This is indeed a mystery,” I remarked. “What do you imagine that it means?”

    “I have no data yet. It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. But the note itself. What do you deduce from it?”

    Seems appropriate to Trenberth!

    Paul

  31. “There was surprise amongst the global scientific community when confronted with observations showing that the evaporation of water from pans has been, on average, declining over the last 30–50 years just as global temperatures have been rising. Surely this must be a hoax!

    “As it turns out, though, it is not a hoax. Instead, it is one of those unexpected observations that stimulate the very best science. Understanding and unraveling the ‘pan evaporation paradox’ underpins the whole question of how water availability has changed and might change.”

    Roderick’s analysis of radiation, temperature, humidity and wind speed measurements has been comprehensive. He has shown that several factors are at work simultaneously, with declining wind speed and/or declining radiation being the major global factors behind declining evaporation. All these must be taken into account with errors declared clearly.’

    http://www.control.com.au/bi2009/310ASPrize.pdf

    ‘Globally, precipitation can be approximated by surface evaporation, since the variability of the atmospheric moisture storage is negligible. This is the case because the fluxes are an order of magnitude larger than the atmospheric storage (423 × 1012 m3 year−1 versus 13 × 1012 m3 according to Baumgartner and Reichel (1975)), the latter being determined by temperature (Clausius–Clapeyron). Hence the residence time of evaporated water in the atmosphere is not more than a few days, before it condenses and falls back to Earth in the form of precipitation. Any change in the globally averaged surface evaporation therefore implies an equivalent change in precipitation, and thus in the intensity of the global hydrological cycle. The process of evaporation requires energy, which it obtains from the surface radiation balance (also known as surface net radiation), composed of the absorbed solar and net thermal radiative exchanges at the Earth’s surface. Globally averaged, this surface radiation balance is positive, since radiative absorption, scattering and emission in the climate system act to generate an energy surplus at the surface and an energy deficit in the atmosphere (Liepert 2010). Evaporation, or more precisely its energy equivalent, the latent heat flux, is the main process that compensates for this imbalance between surface and atmosphere, since the latent heat dominates the convective energy flux over sensible heating. The radiative energy surplus at the surface is thus mainly consumed by evaporation and moist convection and subsequently released in the atmosphere through condensation. This implies that any alterations in the available radiative energy will induce changes in the water fluxes. Our focus in this editorial is therefore on the surface radiation balance as the principal driver of the global hydrological cycle.

    http://iopscience.iop.org/1748-9326/5/2/025203

    ‘Complex interactions in the climate system can give rise to strong positive feedback mechanisms that may lead to sudden climatic changes. The prolonged Sahel drought and the Dust Bowl are examples of 20th century abrupt climatic changes that had serious effects on ecosystems and societies. Here we analyze global historical rainfall observations to detect regions that have undergone large, sudden decreases in rainfall. Our results show that in the 20th century about 30 regions in the world have experienced such changes. These events are statistically significant at the 99% level, are persistent for at least ten years, and most have magnitudes of change that are 10% lower than the climatological normal (1901– 2000 rainfall average). This analysis illustrates the extent and magnitude of abrupt climate changes across the globe during the 20th century and may be used for studying the dynamics of and the mechanisms behind these abrupt changes.’

    http://cursoprevisores.wikispaces.com/file/view/fernando.pdf

    It is as usual complex and dynamic – weather and climate are chaotic.

    In Australia – as in a large part of the world – precipitation max. and min. are associated with ENSO – which shifts abruptly on decadal scales.

    There is no ‘trend’ in extreme precipitation.

    http://www.bom.gov.au/cgi-bin/climate/change/extremes/timeseries.cgi?graph=R99p&ave_yr=0

    Climate is orders of magnitude more complex than climate models.

    • I should make it clear that looking at ‘trends’ over 60 years is very misleading because of decadal variability in both the NH and SH.

    • Robert – Although individual regions will differ, the best evidence we have suggests that global precipitation extremes have been increasing. The data from Min et al aren’t completely global, but involve more coverage than other datasets I’m aware of. Regarding Australia specifically, its trends may be most likely to reflect the fact that Southern Hemisphere warming has been slower than in the Northern Hemisphere, but any individual region within the globe might differ from the overall trend..

      The editorial you link to from Martin Wild, as well as his original papers, indicates why warming trends and pan evaporation trends are likely to diverge. Pan evaporation is dominated by daytime absorption of solar radiation, and during intervals when insolation was declining from increased anthropogenic aerosols (e.g.,about 1950 to the late 1970s), evaporation would have been suppressed. Even when nighttime temperatures were increasing due to increased greenhouse effects, that process could not fully offset the reduced insolation. A reduction in wind speeds due to a reduction in the thermal gradient from low to high latitudes also contributed.

      • Chief Hydrologist

        Fred,

        I linked to a paper adressing abrupt hydrological change in 30 regions of the Earth. Rainfall is chaotically variable – both spatially and temporally. One of the modes of NH variability involves the Northern Annular Mode with a low frequency modulation of 40 to 80 years. The simple point is that short term variability – even those from 1951 – are not reliable indicators of any anthropogenic ‘trend’ at all.

        When I speak about the evapotration paradox – I am speaking of the last few decades where increasing temperature was accompanied by reduced pan evaporation measures globally. It is a different problem to the insolation problem.

        Essentially – Wild simply and quite sensibly in the hydrological world – says that evaporation = precipitation – mositure in the atmosphere is irrelevant. Even if the residence time in the atmosphere is reduced by some mechanism – the law of conservation of mass applies. There is no reason why warming – that is largely due to natural factors at any rate – should result in more rainfall. The conceptual framework for higher intensity rainfall invloves more water in atmosphere that is suddently dropped out in rainfall – but the change atmospheric moisture is trivial and only a portion of that appears as rainfall.

        There is no ‘trend’ in Australia over the 110 year instrumental record – either in totals or extremes of rainfall. There is no trend globally in rainfall totals – a slight increase in totals over the course of the 20th century in many places – including the US and Australia – indistinguisable from a background variability.

        Quite a lot of the decadal global hyrological variability is associated with the ENSO and the Pacific Decadal Variation – changes in rainfall in Australia, Indonesia, China, Africa, India and North and South America. I suspect that much of the insolation changes discussed by Wild and many others are the result of ENSO cloud radiative feedback.

        I don’t pretend to know all the answers – the problem is complex and dynamic with multiple feedbacks at scales at the molecular level to near global sized systems. A simple narrative will not do – we need to look at a range of data and synthesis conclusions that are not neccessarily correct.

        ‘Uncertainty is an uncomfortable position. But certainty is an absurd one.’
        — Voltaire

  32. Australia’s climate is affected by ENSO. Pielke Jr. has posted on a study by an Australian climate scientist that heavy rains, and flooding, flow from La Nina. Why would anyone who is knowledgable claim that global warming caused this year’s flooding, especially since papers are being written excusing the lack of global warming because of aerosols.

  33. The decrease in evaporation over the late 20th century has been known about for a long time – it is known as the evaporation paradox if you want to google it.

  34. Chief Hydrologist

    ‘Complementarity’ over landscapes involves limitations in soil moisture. Thus if evaporation is greater – then soil moisture decreases and evapotranpiration is lower and vice versa. I wonder about the effect of plant stomata size and density decreasing with increasing CO2 – and the implications for terrestrial water cycling – the decrease in evapotranspiration with increasing CO2 should be a factor in local climate and dew point condensation – which in turn influences soil moisture.

    Over oceans where the hydrological cycle largely has it’s origins – there is of course no moisture limit and no evapotranspiration. Over oceans it it the radiative balance at the surfuce that drives latent heat. The decrease in pan evaporation is seen globally – it may be as simple as the increase in spefific humidity in the troposphere. I am assuming it is the case over the oceans as well.

    • I think Martin Wild’s explanation above (from your link) of the pan evaporation effect is cogent. Increased specific humidity should not reduce evaporation if relative humidity doesn’t increase. Immediately above ocean surfaces in the tropics, the air is nearly saturated, and so changes in wind speed and boundary layer turbulence are probably more important determinants of evaporation rates.

      • More data reinforcing the interpretation of pan evaporation declines as a response to declining insolation and wind speed, including a recent regional reversal of the pan evaporation decline in concert with increasing air temperature, is found in the recent GRL paper by Zhang et al.

      • Steve Fitzpatrick

        Fred,
        I think Chief Hydrologist is right about this. The total evaporation from the ocean surface, especially in the tropics and subtropics, is mainly controlled by net solar energy absorption. It is basically an energy balance constraint; if the evaporation rate were to fall (say due to a reduction in wind speed or turbulence) then the water surface temperature would pretty quickly rise until the evaporation rate was restored to near it’s previous level. There is just too much energy that has to be dissipated for there to be much (as a fraction of the total flux) imbalance .

      • Steve – That doesn’t seem to be the case, probably because near surface air is near saturated, and so a warmer ocean surface can’t contribute much to evaporation unless the air “makes room for it” through dissipation of the local humidity via wind and/or turbulence. I’m not stating that absorbed ocean energy is irrelevant – ultimately, a warmer surface will warm the overlying air and therefore increase water-holding capacity – but the main drivers of short term changes appear to be in the atmosphere,

        Regarding absorbed energy dissipated in latent heat flux, about 1/3 comes from solar radiation and 2/3 from “back radiation” of infrared energy from the greenhouse gases in the atmosphere.

        I think Isaac Held has blogged on this recently, and I will try to find his post.

      • Steve Fitzpatrick

        Fred,

        Where the radiative forcing comes from (CO2 back radiation or increases in net absorbed solar radiation) does not seem to me to make a lot of difference. If we look at the process of heat flux from the ocean surface, it basically consists of two parts, infrared radiation (passing through the atmosphere’s IR window, at least in the absence of overlying clouds) and convective/latent heat transport. If increased CO2 and increased water vapor narrow the IR window (or equivalently, ‘the back radiation increases’), then a simple energy balance demands that convective/latent heat transport rise to compensate. For sure the total global precipitation ought to increase (as Wentz et al have shown), because more for the surface heat flux is in the form of moist convective transport, which automatically leads to more rain.

        The air temperature above the ocean surface (certainly in the tropics and subtropics) is essentially the surface temperature of the water… the moisture carrying capacity of the air immediately over the water increases if the ocean surface temperature rises; the moisture holding capacity in fact rises in direct proportion to the vapor pressure of water. Warmer water means warmer surface air and more moisture holding capacity; the two are tightly linked; there is no “eventually” involved in the process.

      • The increase in surface temperature will also lead to an increase in IR radiation loss that may cancel most of the back radiation increase leaving a small residual to increase or decrease latent heat flux. It is far from obvious that the global latent heat flux will increase in a CO2-doubled environment.

      • It’s mirrors all the way down the decline function.
        ============

      • the moisture holding capacity in fact rises in direct proportion to the vapor pressure of water.

        I don’t think there is a reason why this should be so. It is the air temperature, not the water temperature, that determines the capacity to hold moisture. We agree that ocean skin temperature and surface air temperature are linked, but the link is not the sole determinant of latent heat flux. Depending particularly on wind speed, absorbed energy will be distributed differently between ocean heating and latent heat transfer to the atmosphere, and so increased heating will not necessarily restore latent heat transfer to a previous value..

        Note that the surface/air link is due to conduction, not IR radiation. Without conduction, there would be a surface/air discontinuity. If the ocean surface is impeded in releasing energy via latent heat transport, by reduced wind speed for example, it will heat more, and some of that heat will be emitted upward as IR, bypassing the conductive pathway, and eventually escape to space. That means that latent heat flux (via evaporation) will decline, because more energy is escaping via a different route even though the total energy absorbed hasn’t changed. Over the long term, these effects may average out, but over short intervals, a reduced wind speed will shift the balance from latent heat transfer toward IR flux.

        Perhaps we are talking at cross purposes. Without question, an increase in absorbed radiation will mediate an increase in evaporation. My point relates to the factors that can significantly modify the magnitude of that effect at any given level of absorbed radiation..

      • Chief Hydrologist

        ‘The radiative energy surplus at the surface is thus mainly consumed by evaporation and moist convection and subsequently released in the atmosphere through condensation. This implies that any alterations in the available radiative energy will induce changes in the water fluxes.’ Wild 2010

        I am sorry I mentioned pan evaporation.

        But I think you have nailed it – good explanation. .

  35. They keep digging and digging to find connections with anthropogenic global warming and come up with nothing. But they have to cover that up somehow so they fudge it like this: ” While perhaps a major part of these high sea surface temperatures was related to natural variability such as ENSO [El Nino Southern Oscillation], a component is related to global warming. It is when global warming and natural variability come together that records are broken.” They don’t even do that right. A “component?” How do you know that? And that is what you think leads to broken records? Give me a break. ENSO has a warm phase (El Nino) and a cool phase (La Nina). They are accurately known. To point to ENSO without specifying its phase or timing is meaningless. Still, with 3.5 billion dollars to spend on climate research each year the funding is there for any unlikely proposal that promises to uncover such connections.I get that number from issue 2 of Nature Climate Change. According to them part of it comes from foundations. If that number is accurate two thirds of it is foundation money and one third comes from Uncle Sam directly. It settles one mystery for me: how is it possible for ten thousand parents to send their children to take part in student protests in Copenhagen? It had to be foundation money. Getting those foundation billions to support the global warming movement is a real achievement for their propaganda machine. Money talks, politicians listen, and the result is a series of irrational laws to prevent an imaginary global warming disaster which carbon dioxide is supposed to bring upon our heads.

  36. Chief Hydrologist

    What Wild says is that insolation changes are the driving force for evaporation – ‘Evaporation, or more precisely its energy equivalent, the latent heat flux, is the main process that compensates for this imbalance between surface and atmosphere, since the latent heat dominates the convective energy flux over sensible heating. The radiative energy surplus at the surface is thus mainly consumed by evaporation and moist convection and subsequently released in the atmosphere through condensation. This implies that any alterations in the available radiative energy will induce changes in the water fluxes. Our focus in this editorial is therefore on the surface radiation balance as the principal driver of the global hydrological cycle.’ Wild says nothing about the pan evaporation paradox.

    The pan evaporation paradox is a separate problem – does it even exist over the oceans? I am assuming it does because – because it is seen in pans close to oceans as well. If so why?

    When you assume constant relativity it is an assumed average and not a reality. What is measured is the change in specific humidity.

    http://www.ipcc.ch/publications_and_data/ar4/wg1/en/figure-3-20.htm

    Specific humidity – and relative humidity – changes in complex ways over a day – a season – a year and longer. Simple answers will not do – and repeated assertions will not convince.

    • Wild’s JGR 2009 article addresses the pan evaporation phenomenon as a competition among insolation, wind speed, and relative humidity changes from changing air temperatures – see section 2.3.4. The interval of declining evaporation is coincident with decreased daytime insolation and probably reduced wind speed. Some reversals have been observed in areas where increasing air temperature increases the water-holding capacity of the atmosphere.

      • Chief Hydrologist

        There are two issues – the question of decreasing pan evaporation – for which there are limited variables according to the Penman equation – insolation, wind speed and relative humidity. I don’t really know what your point is – except that you seem to be wrong about the direction of evaporation in a warming world – and therefore of precipitation. And don’t like it – and wish only to prevaricate and dissimmulate.

        ‘The Class A pan evaporation rates at many Australian observing stations have reportedly decreased between 1970 and 2002. That pan evaporation rates have decreased at the same time that temperatures have increased has become known as the “pan evaporation paradox.”

        Pan evaporation is primarily dependant on relative humidity, solar radiation, and wind. In this paper, trends in observed pan evaporation in Australia during the period 1975–2004 were attributed to changes in other climate variables using a Penman-style pan evaporation model. Trends in daily average wind speed (termed wind run) were found to be an important cause of trends in pan evaporation. This result is a significant step toward resolving the pan evaporation paradox for Australia.’

        http://journals.ametsoc.org/doi/abs/10.1175/JCLI4181.1

        So have we solved the pan evaporation paradox – quieter winds in a warmer world? Perhaps not – the complexities are very real and beyond me. I will let others decide if they are beyond you also.

      • Robert – I think it’s fine for others to review these data and make their own judgments. Regarding evaporation in a warming world, the data I’ve linked to indicate an accelerated hydrologic cycle, so evaporation rates have increased. This may not have been inevitable, but it does conform to expectations.

      • Chief Hydrologist

        There is no indication anywhere that preciptation has increased – so no evaporation has not increased at the same time as global pan evaporation decreased.

        Apart from Jim’s notion on orographic rainfall.

        precipitation = evaporation.

      • The data I cited above from the GRACE study and from Min et al contradict that conclusion and indicate that evaporation has increased. In preference to a repetition of claims here, readers can visit these references to draw their own conclusions.

      • Chief Hydrologist

        ‘There is indication for a suppression of greenhouse-induced warming through ‘‘global dimming’’ between the 1950s and 1980s, and an enhancement through ‘‘brightening’’ between the 1920s and 1940s as well as from the 1980s onward.’ Wild 2009

        It is generally agreed that pan evaporation has been decreasing over much of the world over the past half century. Hence the paradox.

      • The Zhang et al paper reports a reversal of the decline, at least regionally, associated with significant rises in air temperature. Is there still a paradox? Perhaps, but reduced insolation was only one factor – wind speed decline was another, due to reduced latitudinal gradients. Those have probably not reversed, because they are a consequence of increased warming driven in large part from the tropics.

      • Chief Hydrologist

        ‘Despite the observed increases in global average temperature, observations across the world show that the rate of pan evaporation at a regional scale has been steadily decreasing over the past 50 years. This is known as the pan evaporation paradox. This paper reviews current reported pan evaporation trends, examines available theoretical explanations about this “paradox”, and discusses current research gaps and priorities. It concludes that: (1) three major potential causes of pan evaporation, solar radiation, vapour pressure deficit (VPD) and wind speed, have been changing in the last 50 years. The magnitude of changes and importance of each of these three causes varies from region to region, as does the pan evaporation trend, although overall there is a decreasing trend. (2) Currently two existing theories explaining the pan evaporation trends have limits and are only valid in some specific regions and seasons. Neither of them provides a fundamental physical-based theory that could be applied everywhere. (3) Further investigations are needed before we can fully understand the global evapotranspiration trend in global warming scenarios.’

        http://www.springerlink.com/content/q7g707605j4n4746/

      • These factors have been discussed in above comments, including the Wild JGR paper I linked to. Your point from the link you give may be that the balance among all relevant variables hasn’t yet been established on the basis of some more fundamental principle – I can’t judge that because the paper you linked to is freely available online as an abstract – but the main factors are those discussed above.

      • Chief Hydrologist

        http://www.science.org.au/natcoms/nc-ess/documents/nc-ess-pan-evap.pdf

        I don’t know where you are going with this Fred and I think you need some detailed background. This is definitely my field and not yours. The pan evaporation issue is complicated – different effects are important regionally and at different times. It is perhaps also of more than passing interest only to water engineers and agronomists. There is no point to be made of any significance.

        The best information is on rainfall – and that is questionable in good part. Globally average rainfall has increased by 2% since 1901. Not significant in other words. It implies that total evaporation hasn’t increased either – because by mass balance evaporation must equal rainfall.

        You talk about an ‘accelerated hydrological cycle’ – and I can only imagine that to mean that evaporation increases and therefore rainfall as well. But that is not the case from precipitation records.

      • Robert – I’m not sure too many other readers are interested in these details sufficiently for us to further pursue the point. I’ve cited evidence for an increased hydrologic cycle, which entails increased evaporation and precipitation. As atmospheric water content rises,the rate of precipitation won’t quite match evaporation, but will be very close. A 2% rise would seem to involve an enormous quantity of water, but I also wonder whether the other measures of hydrologic cycle rate such as the GRACE data aren’t a better way to arrive at precise figures than rainfall records. Unfortunately, GRACE didn’t start until 2002, so we may not have good data that goes back a long way globally.

      • Chief Hydrologist

        You reference a paper that discusses extreme precipitation changes in the NH since 1951. I suggest that has more to do with persistent blocking patterns in low frequency modulation of the NAO especially – and that use of a longer record would change the complexion of the results.

        You reference a GRACE powerpoint on short term changes in the water storage compartments. Interesting as such work is and valuable in the future – it is certainly not possible to reliably distinguish any trend or causality in such a short record.

        2% of total global rainfall is an enormous amount of water but well within the error limits of the data. The best long term record we have on rainfall is the precipitation records. It shows a statisticallhy insignificant increase in global total precipitation – so no evident increase in evaporation since 1901.

      • Yes evaporation must equal precipitation. So, if evaporation from slightly warmer oceans hasn’t increased, or has only slightly increased, what can have caused this?

        Maybe an increased level of humidity? Is this evidence for a positive feedback?

      • Chief Hydrologist

        Warmer air holds more water vapour – the problem is in attributing warming. Most recent warming (1976 to 1998) occurred in 1976/77 and 1997/98. These are defined as extrene events associated with noisy bifurcation, catastrophe in the sense of Rens Thom, abrupt change… http://arxiv.org/ftp/arxiv/papers/0907/0907.4290.pdf Most of the rest occured as a result of the PDV cloud feedback.

        There are a few things that influence avaporation – water vapour deficit, wind speed and air temperature. The water vapour dificit is always to be constant over the oceans at least, the effect of wind depends on drier boundary conditons so is less of an issue over the oceans – leaving the sun to heat the water resulting in a net IR up, a latent heat flux and a bit of sensible heat. Evaporation is driven by insolation. Did insolation change? Perhaps a little on interannular to decadal scales – mostly due to ENSO and PDV cloud feedbacks – but not a lot in proportion to the total incoming energy from the Sun.

      • Chief Hydrologist

        It does rain and snow more in a warmer world than in a cooler. But there is no evidence of much change at all.

    • Chief Hydrologist
      WJR Alexander (see citations above shows pan evaporation does NOT vary with the 21 year Hale cycle, but that precipitation, runoff and floods do vary repeatably with the Hale cycle in the Southern Africa region – based on > 11,000 records covering > 100 years.

      Do you know of any other comparable studies elsewhere testing evaporation vs precipitation, runoff and floods against the Hale cycle?

  37. While more water vapor doesn’t guarantee more rain, a situation to look at more closely is orographically forced rain. As air comes off a warmer ocean, it holds more moisture, which when lifted over a mountain range deposits and amount proportional to the water it contains. This would seem to be a special case where more moisture does guarantee more rain. So if I was looking for locations with more flooding, it would be rainy upwind slopes of mountain ranges exposed to air flow from the oceans (e.g. western US, Norway, etc.).

  38. In response to a query by Frank “TRC: If temperature is rising and precipitable water is falling then relative humidity must be falling. Can you tell us where your data is from and possibly explain why most other sources suggest that relative humidity is constant? Thank you”.
    Frank, you are right, and both the specific and relative humidity have indeed been declining strongly since 1948 at all 3 of the Atlantic, Pacific and Indian oceans , with RH falling by as much as 0.1774% p.a., 0.223% p.a. and 0.0514% p.a. respectively between 1948 and 2010.

    It has always amazed me how few pages of data there are in the 996 pages of the IPCC’s Solomon et al 2007 – and you will not even find the terms relative and specific humidity in the Index! The same is true of pan evaporation, equally missing in IPCC action, apart from the special pleading at p.260 and p.279 to explain away the substantial evidence for falling pan evaporation.

    However diligent search by me has found brief references to allegedly rising PW, along with constant RH, and rising upper-tropospheric SH at p.238 of AR4 WG1 Solomon et al. – but unburdened by any supporting data. The ESRL data for RH and SH cited above are both for 300 mb pressure level.

    The likeliest explanation is that Solomon et al rely heavily on allegedly rising precipitable water (and SH) to achieve their 3-5 oC temperature sensitivity for 2X CO2. So falling PW, RH, and SH do not fit the story line and are therefore totally expunged, or simply reversed by a snap of Trenberth’s fingers, as inferred here by BobN.

    My data come from http://www.esrl.noaa.gov/psd/cgi-bin/data
    You can specify the variable of interest to you and the latitude and longitude of which ever ocean, land mass, or other locality you want.
    The reanalysis data there are explained in Kalnay, E. et al. 1996. The NCEP/NCAR Reanalysis 40-year project. Bulletin American Meteorological Society, 77, 437-471.

    • TRC,

      What parameters are there missing in the data and logic to come up with an overall calculation?
      When latitude and longitude are used, is not the speed of planetary rotation different as well? Smaller planetary diameter mathematically is a faster speed of rotation when you unwind the circumference and measure the distance. Science is still equating this planet as a cylinder and NOT smaller as you go to the poles with different variables.
      Past theories equate this planet as not loosing a single molecule of water vapor. Yet any object hitting the atmosphere generates a splashing effect. Moon is full of craters of objects hitting it, yet we only have minimal damage to show from the time of creation.
      What happened to the OLD volcanic activity? We have mountains rising out of water yet no extremely old evidence of volcanic activity.
      Salt evidence is abundant that we have had much more water on this planet which would absorb and distribute shock damage from huge objects hitting this planet.

    • TRC – While it is true that specific humidity appears to be decreasing in the uppermost levels (300 mb) of the troposphere if you look at the NCEP reanalysis data for lower levels (e.g., 1000 mb, 850 mb), the specific humidity levels have been rising since about 1960 or so. Since the lower tropospere holds so much more water than the upper tropospere, there has been a slight increase in specific humidity over the past 50-60 years.

    • TRC: Thanks for the reply. I was under the impression that satellite data has consistently shown that absolute humidity is rising and that relative humidity has remained roughly constant. The idea that humidity has been falling in the longer term apparently comes from older radiosonde data, which even skeptics such as Spencer suggest can’t be trusted in the upper atmosphere. That older radiosonde data has been processed (or cherry-picked) in several publications to generate results that support rising absolute humidity. (I’m currently agnostic about all older radiosonde data.)

      Different re-analyses apparently give different trends in absolute humidity. The problem with re-analyses is that during recent years the output is dominated by observations (especially new observations from space) whereas in earlier years limited observations permit more model bias to distort the output, thereby biasing trends. Since re-analyses have this flaw and give contradictory trends, I am currently discounting all of the reanalysis data.

      From my perspective, this leaves only the satellite record; but others may disagree. I am open to any new information that contradicts my current understanding – which is why I asked where your data came from.

  39. Judith: If we judge by Steve Schneider’s standards, Trenberth is obviously speaking here as a policy advocate (using simplified dramatic statements and scary stories) rather than an ethical scientist scientist (tell the truth, the whole truth … with all of the caveats …) Such alarmism appears to come from the same intellectual cesspool as denialism. Shouldn’t both be treated with equal disdain? Isn’t Trenberth’s statement the same type psuedo-science being pushed by “deniers” (DLR is inconsistent with the 2nd LoT, DLR can’t warm the ocean, Sky Dragons, etc)?

    Rainfall is caused by temperature decreasing in parcels of atmosphere, not the “holding capacity” of the atmosphere. Increasing vertical convection can increase rainfall by producing a greater temperature change, but increasing convection appears to constitute a negative feedback that reduces surface warming compared with the upper atmosphere (where radiative forcing is controls climate change).

  40. comparisons between Astronomy and Climate Change science or lack thereof are totally bogus. For one thing Astronomy is a science of the past and it’s got lots of it to investigate , compare, make hypotheses about etc. Climate change is a thing of the future, and it’ll stay like that for decades, or forever.

    The Wikipedia entry about using Cepheid variable stars as “standard candles” should suffice to stop any further comparison with AGW and its likes.

    Notably controversy is not alien to Astronomy but eg people not convinced by 96% of the universe being almost undetectable are NOT called “Dark Energy Deniers”. AND all data is ALWAYS shared: even the supersecretive Kepler mission has a sharing policy. No FOI requests are needed, there’s no crybabies parading as “scientists” to deal with, and there’s no strong-armed tactics by any Astro-Mann to ruin the field.

    • omnologos,

      A great deal of science moved away from actually measuring and calculating distances, speed, motion, etc.
      There is a great deal of fiction that is called science but looked at misses many parameters that could disprove the theories.
      String theories and all the garbage around that fails to incorporate circular planetary motion and solar movement of the distance and speed of the solar system.
      This then generates NO actual object is space to triangulate an exact point of stopped space. Any machine created can never find an exact point to send particles or receive particles. String theories rely on point to point calculations.
      Just like the collider NEVER considered that molecules rotate differently from planets. So what garbage is their that can be learned?

  41. ‘This paper describes the results of an analysis of trends in short duration (1–7 days) extreme precipitation events that have a recurrence interval of 1 yr or longer for stations in the United States and Canada. This definition of extreme precipitation was chosen because such events are highly correlated with hydrologic flooding in some U.S. regions. The dominant temporal characteristic of a national event composite index is significant low-frequency variability. There were lengthy periods of a below-average number of events in the 1930s and 1950s and an above-average number of events in the early 1940s, early 1980s, and 1990s. Regional variations often differ substantially from the national composite. A simple linear analysis indicates that the overall trend covering the period 1931–96 has been upward at a highly statistically significant rate over the southwest United States and in a broad region from the central Great Plains across the middle Mississippi River and southern Great Lakes basins. The national trend for the United States is upward at a rate of 3% decade−1 for the period 1931–96. While the annual trend for Canada is upward for the period 1951–93, it is not statistically significant. Although the high statistical significance of the results is partially a consequence of the low frequency during the 1930s and 1950s located in the first half of the record, the latter half of the record exhibits an upward trend nearly identical to the entire record. However, an analysis of a 101-yr record of midwestern stations shows that heavy precipitation event frequencies around the turn of the twentieth century (1896–1906) were higher than for other periods of comparable length, except for 1986–96. Although data were not available in digital form to extend the analysis back to 1896 for the entire United States, the midwestern analysis shows that interpretation of the recent upward trends must account for the possibility of significant natural forcing of variability on century timescales.

    http://journals.ametsoc.org/doi/full/10.1175/1520-0442%281999%29012%3C2515%3ALTTIEP%3E2.0.CO%3B2

    • Chief,

      A couple points to consider.
      At a certain point of latitude, river flows are moving north and south.

      Next point is that some flooding events occur many miles away of extreme precipitation that generates a massive flow at times of much more than one river. These can take many weeks to get to a flood plain. It can generate different peaks of cresting depending on how much more flow is generated by more precipitation further upstream or create another cresting.

  42. Tomas Milanovic

    While there is consensus on this thread that available data show that an increased surface temperature doesn’t lead to an increased rate of extreme events (floods) there is not consensus in whether increased surface temperatures lead to increased precipitation or not.

    In that matter (and I precise that I am not an expert of hydrological cycles) I am pretty much on the same line as The Chief.
    There is no obvious reason that temperature acts directly on precipitation.
    So the argument as it was exposed here is indirect as follows :
    1) increased surface temperature increases evaporation
    2) one admits that evaporation = precipitation
    3) ergo increased surface temperature increases precipitation

    The problem? Oceanic evaporation is not measured and is totally unknown.
    What is measured is precipitation and this very uncompletely as far as spatial and temporal resolution is concerned.

    So then appear at least 2 additional problems.
    First is 2) really, absolutely and always true?
    Second does precipitation really increase?

    Let’s evacuate fast the second. It doesn’t or, if one wants, the incertitude is as large as the signal. So at best, we don’t know.

    But I find 2) interesting. It can be seen as a mass balance or an energy balance.
    Of course as we know, the system is never in equilibrium. So there is no reason that evaporation latent heat = condensation latent heat. Especially as the non radiative energy transfer is much smaller than radiative energy transfer.
    From that follows that the system imposes no very strong constraint on the latent heat transport and that 2) can’t be inferred from energy considerations.
    The system could very well and sustainably maintain an imbalance in latent heat transfers and change the sign of the imbalance according to long period oscillations.

    So what stays is the mass balance. But also here I can’t see how 2) can be inferred from a mass balance.
    The right mass balance would say : evaporated water = condensed water.
    But as condensed water = cloudiness + precipitation, the mass balance says
    evaporation = cloudiness + precipitation and we all know that cloudiness is not equivalent with rain.
    So the only thing we can say is that a warmer surface temperature would lead to more clouds and/or precipitation with unknown proportions. Measuring only precipitation without measuring simultaneously the cloudiness would give a verry misleading information about evaporation.

    But of course and again, as we know that the system is not in equilibrium, neither the cloudiness nor the ratio precipitation/cloudiness is constant.
    Both must oscillate on long time scales while they interact with other long time scale oceanic oscillations.

    From that follows that 2) is certainly wrong in this formulation and that the sign of variation of precipitation with surface temperature is unknown.
    Very parcellar available evidence seems to say that these 2 are independent variables in the very small variation range (a few degrees) that we have observed sofar.

    • Hi Tomas,

      I think I am truly puzzled rather than certain. I have seen paleoclimatic graphs showing low rainfall – from isotopes of oxygen and very approximate – at glacials.

      In some sense it seems correct that evaporation is greater with higher temperatures – but it is not a simple relationship. It is probably truer to say that evaporation is driven by insolation – which changes dramatically over decades at least. And by changes in specific humidity – and thus the water vapour deficit – over oceans. By that I imagine that warmer nights in particular lead to less water dropping out as condensation – so that average humidity remains higher. Is this the true greenhouse gas signature? The other factor that is generally considered over land is wind speed. But that is for small water bodies surrounded by land giving drier boundary conditions. The boundary conditions over oceans are much different – and these empirical relationships used for agriculture are not relevant.

      When considering rainfall – a record as long as possible is required because of natural (and abrupt) variability seen in the instrumental record at scales of up to 80 years. Typically no more than 100 years of data is available and the earlier records are of variable quality and there is limited coverage (from island records) over the oceans. However, the longer term records shows insignificant changes in total global rainfall.

      ‘Globally, precipitation can be approximated by surface evaporation, since the variability of the atmospheric moisture storage is negligible. This is the case because the fluxes are an order of magnitude larger than the atmospheric storage (423 x 10^12m3/year versus 13 x 10^12m3.’

      http://www.nwra.com/resumes/liepert/pdf-files/Wild_Liepert_ERL_EditorialProof.pdf

      So we can approximate the mass balance as:

      precipitation = evaporation – and show indirectly that evaporation hasn’t increased because rainfall has not. .

      Cheers
      Robert

    • “there is consensus on this thread that available data show that an increased surface temperature doesn’t lead to an increased rate of extreme events (floods) there is not consensus in whether increased surface temperatures lead to increased precipitation or not.”

      Tomas – It’s important to distinguish extreme precipitation frequency, which has been shown to increase, from increased floods, where there is no consensus but rather a lack of more than regional data. The increase in extreme precipitation events is consistent with evidence for an accelerated hydrologic cycle.

      Increased precipitation extremes is not the same as increased precipitation overall. Whether increased surface temperatures lead to increased precipitation is a complex issue, because evaporation (and hence precipitation) involves both a temperature effect and a humidity effect allowing the air to accept additional moisture. In fact, the evidence to date, while not based on sufficiently long term global data for high confidence, suggests that at least recently, evaporation and precipitation have increased, as would be expected in a climate that is warming while relative humidity has remained fairly stable.

      • Tomas Milanovic

        Fred

        Well this thread is about “flood peaks” and there is consensus (on this thread) that they didn’t vary. Unless you think that they did in which case we have a “climate science” kind of consensus (e.g your opinion doesn’t count :)).
        50 mm precipitation seems to be neither extreme nor flood causing.

        Then indeed as you confirm, there is no consensus about the question whether increased surface temperatures lead to increased precipitation.
        I have read the 2 pages you linked to but sorry, it is really sub-par article and I don’t know who could be convinced by that.
        In any case as far as I am concerned if the main arguments of an article are :
        1)The Earth system is in equilibrium
        2)We have run N computer models with M conditions for K years with Z parameters (and in this case N,M,K and Z are not even specified)
        3) We did all kind of averages on the computer just because we can

        I rarely bother to read more because experience showed me that this kind of “papers” will be reversed in a few months when somebody else will run a computer and change N,M,K or Z.

        Then

      • I won’t belabor the point, Tomas, but data indicating that flood peaks didn’t show a statistically significant upward trend in a regional analysis is not evidence for how they have behaved globally, nor was there a consensus on this thread that I could detect about global behavior of flood peaks. My sense is that we simply don’t have enough data to judge this latter point, and so I remain agnostic about it.

        Your point about the Min et al paper is incorrect. They reported observational data on precipitation extremes, and then compared these with the modeled data. There was an agreement between the two on the upward trend, but the models underestimated the increase found from the observations. Your prediction that these observations will be reversed in a few months is one I don’t share, but I will be monitoring the literature over the next few months to see whether you are right.

  43. The Villarini studies do not challenge evidence of climate change (e.g. in the Eastern U.S.) and are not the first or only studies to consider anthropogenic nonclimatic changes e.g. land-use, water engineering.

    These are extremely important investigations for science and society, and are largely about decisions related to whether water management practice needs to change based on climate change effects, so this is an especially important evolving discussion in the water management and agricultural communities.

    • Vaughan Pratt

      The Villarini studies do not challenge evidence of climate change

      My point exactly as I argued earlier: one cannot rule out a causal relation from A to B merely on the basis that B changes faster than A, which is the extent of their argument. That would be like proving a bullet is harmless because the trigger doesn’t move fast enough to do any harm.

  44. Tomas Milanovic

    Chief

    precipitation = evaporation – and show indirectly that evaporation hasn’t increased because rainfall has not

    I understood that this was the argument . I also know from the theoretical side the evaporation relations (and especially the strong dependence on wind).
    My point was on cloudiness.
    When the evaporated water condenses, it doesn’t transform in rain. It transforms in clouds.
    But the clouds don’t transform only in rain either. They reevaporate and recondense elsewhere. They vary in volume . And lastly they partially transform in rain too.
    So a variation in cloudiness is indeed a water storage but even a very small variation in cloudiness may have dramatic impact on energy transfers.
    Even a zero variation in cloudiness with just a different spatial distribution has a dramatic impact on energy transfers.

    For instance you can double the cloudiness at the poles and nothing happens.
    But if you make vary the cloudiness at the tropics even very slightly, you will change significantly all energy fluxes and following the temperature fields and finally evaporation too.
    That’s why the notion of “average” cloudiness is totally useless.
    For a given average cloudiness there is an infinity of spatial distributions and an infinity of energy flux distributions which are very far appart from each other.

    So basically what I am saying is that as condensed water = clouds + rain, it doesn’t follow that evaporation = precipitation.
    This is because in this complex non linear system, the spatial distribution of the clouds matters and if one ignores what the clouds do, one cannot know what the evaporation does even if one knew what the precipitation does.

    My picture of the process would be one in which there are oscillating chaotic patterns of evaporation coupled to cloudiness via the temperature field.
    Then there are oscillating chaotic patterns of precipitation coupled to cloudiness by many things (wind, temperature, topography, pressure).
    I consider that these both patterns behave largely independently or that there is both a time and space lag between them what is almost the same thing. Sure approximately there would be evaporation = precipitation on some time scales but the small difference would be precisely what matters for the global dynamics.

    Then if a spatial correlation between (parts of) both patterns appeared, it would be only an artefact of the chosen time scale. Multiply the time scale by 10 or divide it by 10 and the spatial correlations disappear.
    In any case I deeply agree with Judith when she wrote that increased temperatures don’t necessarily mean increased precipitation (e.g at all time scales).

    • There is so little water in the clouds – and in the whole atmosphere – in comparison to the total annual evaporation that the changes in the cloudiness or moisture just cannot break the close equality of (net) evaporation and precipitation. The word net is, however, important, because the cross evaporation is much larger and largely canceled by the water molecules that return individually from the lowest atmosphere to oceans.

      The gross evaporation is determined by the surface temperatures of oceans (weighted average, not simple average). The net evaporation is determined by gross evaporation and the transfer of moisture from the boundary layer to the rest of atmosphere. This transfer is in turn influenced by many factors including winds and moisture gradients in the atmosphere. Radiation (both solar and IR) affect the net evaporation through the surface temperature. The radiative imbalance maintains the surface temperature at the actual levels, when evaporation causes cooling of the surface.

    • Chief Hydrologist

      Tomas

      You are of right of course.

      But let me make the point first that analysis of rainfall and flooding using records less than the length of the major modes of oceanic and atmospheric multi-dedcadal variation can’t give proper anwers as to hydrological changes. Changes over 60 years for instance may be entirely natural. Flood records are sparse with less than 40 years record in most places. Precipitation is a longer record and more accuate – but prior to pluviuographs it consisted of daily readings of rain guages. So intensity – duration – frequency data is fairly modern as well. In the order of 20 years at most. Data on clouds includes the ISCCP, ERBE and ‘Earthshine’. There are as well some surface observations. The data suggests that there are secular cloud changes that are climatically significant.

      We are talking about short residence times of water in the atmosphere – in the order of days. But while it is there – there are cloud radiaitive effects that seem largely the result of ENSO. Less low leval stratocumulus cloud decreases globally in an El Nino and increases in a La NIna.

      Here is a pan evaporation record for Australia with a 10 year running average. The record is influenced by cloud in La Nina – it forms over cool seas and scuds across the Pacific driven by the trade winds.

      http://www.bom.gov.au/cgi-bin/climate/change/timeseries.cgi?graph=evap&area=aus&season=0112&ave_yr=10

      Here is a total rainfall record for Ausatralia – again with a 10 year running mean. It shows the folly of drawing conclusions from too short a record. Although there are other influences on Australian rainfall – prominently storms spinning of the Antarctic and the Idian Oean dipole, changes in rain totals are dominated by ENSO and the Pacific Decadal Variation. The pattern is for a decrease to the 1940′s, an increase to the late 1970′s and a decline to the climate shift in 1998/2001.

      http://www.bom.gov.au/cgi-bin/climate/change/timeseries.cgi?graph=rain&area=aus&season=0112&ave_yr=10

      Both observers and models are predicting odds on for a return to La Nina conditions in the SH sping. This is the usual pattern for strong ENSO events. It seems obvious given the continued strength of upwelling in the
      region of the Humboldt Current (South America) and in the north east Pacific.

      Some extremes for Australia.

      Heavy precititation days – http://www.bom.gov.au/cgi-bin/climate/change/extremes/timeseries.cgi?graph=R_10&ave_yr=10

      Very heavy precipitatio days – http://www.bom.gov.au/cgi-
      bin/climate/change/extremes/timeseries.cgi?graph=R_30&ave_yr=10

      Maximum one day precipitation – http://www.bom.gov.au/cgi-bin/climate/change/extremes/timeseries.cgi?graph=RX1d&ave_yr=10

      Consecutive dry days – http://www.bom.gov.au/cgi-bin/climate/change/extremes/timeseries.cgi?graph=CDDs&ave_yr=10

      Consecutive wet days – http://www.bom.gov.au/cgi-bin/climate/change/extremes/timeseries.cgi?graph=CDDs&ave_yr=10

      There is little evidence in Australia for anything untoward that can be observed against background variability.

      Which brings us to the study at the top of this thread. It is important to note that the data was for stations that had at least 75 years of record. It is critical for analysis of extremes to have a long record.

      ‘Trend analyses for the 572 eastern United States gaging stations provide little evidence at this point (2009) for increasing flood peak distributions associated with human-induced climate change.’

  45. Roger Pielke Jr emailed me a link to a previous post entitled
    A decrease in floods around the world?

    http://rogerpielkejr.blogspot.com/2011/04/decrease-in-floods-around-world.html

    • The article is an informative summary of data from several recent sources. Despite the title, the data reported show very great regional and temporal variability with no clear overall trend. This is consistent with the many local climatic and non-climatic variables affecting stream flow that can overwhelm any effects from globally averaged changes in temperature or precipitation.

  46. Tomas Milanovic

    This is consistent with the many local climatic and non-climatic variables affecting stream flow that can overwhelm any effects from globally averaged changes in temperature or precipitation.

    I fully agree with this statement. This is precisely the reason why it seems foolish to look for evidence for a hypothetical signal which is so utterly overwhelmed by what is really observed.
    Saying “Oh it’s surely somewhere but you can’t see it.” doesn’t strike like very convincing.

  47. In response to a further query by Frank
    “TRC: Thanks for the reply. I was under the impression that satellite data has consistently shown that absolute humidity is rising and that relative humidity has remained roughly constant….From my perspective, this leaves only the satellite record; but others may disagree. I am open to any new information that contradicts my current understanding – which is why I asked where your data came from.”

    Frank, you may well be right, but I always trust ESRL-NOAA more than Gistemp & co. One answer to your comments is that until 2006 NREL-NOAA published data from 1960 to 2006 at up to 1200 individual locations in the USA which covered a very wide range of climatic variables, all ignored by the IPCC. The monthly time series includes RH and precipitable atmospheric water [H2O]. For Point Barrow in Alaska there are statistically significant upward linear trends in both variables:

    [H2O]
    y = 0.0049x + 0.5448
    R² = 0.6056
    RH:

    y = 0.0765x + 79.78
    R² = 0.1323
    The #3 polynomials have even better fits of course (reflecting ENSO).

    Meantime for Hilo, a town at the base of Mauna Loa mountain, [H2O] shows declining linear and #3 polynomial trends, while RH is totally flat.
    y = -0.009x + 3.5001
    R² = 0.3697
    I might one day do all 1200 locations, but of the score or more regressions that I have done, [H2O] is always the statistically significant determinant of temperature change between 1960 and 2006, while CO2 NEVER plays any role at all. That is why my source is studiously ignored – and none can compete with James Hansen, Gavin Schmidt, Mike Mann, and Phil Jones when it comes to studiously ignoring inconvenient data!

    • Vaughan Pratt

      I might one day do all 1200 locations, but of the score or more regressions that I have done, [H2O] is always the statistically significant determinant of temperature change between 1960 and 2006, while CO2 NEVER plays any role at all. That is why my source is studiously ignored – and none can compete with James Hansen, Gavin Schmidt, Mike Mann, and Phil Jones when it comes to studiously ignoring inconvenient data!

      You seem as anxious as Villarini et al to argue that because water is the culprit, CO2 can’t be. This is like arguing that people don’t kill people, guns kill people, or vice versa, neither of which is sound: it takes a gun and a person.

      If you suddenly burn several hundred million years of accumulation of carbon based fuel and deposit the resulting CO2 in the atmosphere in three centuries, with two-thirds of it emitted in the past half century, on a geological scale this is like striking a gong. You have no idea what vibrations this is likely to cause, in all sorts of phenomena including storms and floods.

      It is not necessary for net evaporation to change in order to have massive flooding, witness the inundation of Fukushima. That did not result from increased humidity but from striking a gong.

      Granted the recent uptick in CO2 does not have the suddenness of the Honshu earthquake, but then neither does the gradual increase in storms and flooding over the past half century have the suddenness of the tsunami that overran Fukushima.

  48. Vaughan Pratt commented on On the attribution of flood peaks.
    in response to a comment by T R C Curtin “I might one day do all 1200 locations, but of the score or more regressions that I have done, [H2O] is always the statistically significant determinant of temperature change between 1960 and 2006, while CO2 NEVER plays any role at all…” Vaughan Pratt said:
    “You seem as anxious as Villarini et al to argue that because water is the culprit, CO2 can’t be. This is like arguing that people don’t kill people, guns kill people, or vice versa, neither of which is sound: it takes a gun and a person.”
    I don’t think it is very scientific to argue from analogies: CO2 is not a gun, and even if there were no people, there would still be large annual fluxes of it between the atmosphere and the planet. The tsunami off Fukushima did result from the striking of a gong, the earthquake, but that had nothing to do with anthropogenic CO2, there have always been earthquakes since long before the CO-based industrial revolution
    When you do move on a bit from gongs and guns, your facts are misleading: “If you suddenly burn several hundred million years of accumulation of carbon based fuel and deposit the resulting CO2 in the atmosphere in three centuries, with two-thirds of it emitted in the past half century, on a geological scale this is like striking a gong”. First, more than half of all emissions from humans’ hydrocarbon combustion since the Mauna Loa record began in 1958 have been taken up by the planet’s biota, and have been the necessary condition for the huge increase in global food production since then (ALL our food is derived from CO2). Secondly, there is not a single instance of a CO2-gong, not for floods, as Villarini et al show so compellingly, nor for any climate event. All such events were evident before large-scale hydrocarbon combustion began around 1750.

    • Vaughan Pratt

      I don’t think it is very scientific to argue from analogies

      Speaking as a logician (one of my areas of expertise) there is nothing unscientific about making the evident illogicality of a given line of reasoning even clearer by applying it to an analogous situation to arrive at a patently absurd conclusion. Villarini argues that CO2 can’t be the culprit because flooding is a sudden event whereas the onset of CO2 is slow. That’s illogical, but not as obviously so as in analogous situations where the exact same line of reasoning leads to absurd conclusions, such as the argument that slow movement of a trigger cannot be the cause of a fast moving bullet.

      CO2 is not a gun

      Of course not, otherwise it wouldn’t be an analogy.

      First, more than half of all emissions from humans’ hydrocarbon combustion since the Mauna Loa record began in 1958 have been taken up by the planet’s biota

      My understanding is quite different. The 8 GtC (gigatonnes of carbon) we’re currently adding annually to the atmosphere breaks down roughly as follows.

      (i) Some 3.5 GtC are staying in the atmosphere. This is the portion that climatologists are concerned about. You appear to agree with the extent of this residue.

      (ii) Only 1-2 GtC are being taken up the land, see for example

      http://bomi.ou.edu/luo/pdf/quanitfying_global_terretrial.pdf

      by Yiqi Luo. This paper discusses the problems in assessing the extent to which plants absorb the extra CO2.

      (iii) The rest, namely 2.5-3.5 GtC if my arithmetic is correct, is going into the ocean where it causes ocean acidification by dissolving calcium carbonate to produce calcium bicarbonate.

      As far as global warming is concerned, it is the 3.5 GtC accumulating in the atmosphere today that is of concern. Regarding ocean acidification, the 2.5-3.5 GtC going into the ocean is expected to be highly damaging to much (though not all) of the ocean’s crustacean life. So at least 75% of our emissions have no evident benefit.

      Regarding the remaining 12-25% taken up by the land, one may ask whether plants realize any net benefit by being supplied with more than their usual amount of CO2. This question has been extensively researched over the past decade here at Stanford and elsewhere by Hal Mooney, Peter Vitousek, etc, addressed in a number of papers accessible via

      http://dge.stanford.edu/DGE/Dukes/JRGCE/publications.html

      One significant finding, reported in

      http://www.sciencemag.org/content/298/5600/1987.full

      is that net primary production (NPP) is increased by increasing temperature, precipitation, and nitrogen deposition, all of which are a likely consequence of global warming. It was also found that elevated CO2 without these other consequences of global warming would also increase NPP. The surprising thing was that when all four variables were increased as consequences of global warming, increasing CO2 paradoxically decreased the net benefit to NPP of higher temperature, precipitation, and nitrogen.

      and have been the necessary condition for the huge increase in global food production since then (ALL our food is derived from CO2)

      The past half century has seen a huge increase in crop yields per hectare, see

      http://www.oecd.org/dataoecd/22/53/1881669.pdf

      You seem to be claiming that if the CO2 had stayed at 300 ppmv instead of rising to 390 ppmv then this increase in yield could not have been achieved. I would be very interested in seeing a basis for this claim.

      Secondly, there is not a single instance of a CO2-gong, not for floods, as Villarini et al show so compellingly, nor for any climate event. All such events were evident before large-scale hydrocarbon combustion began around 1750.

      What I’m referring to as a “gong on a geological time scale” is the present rate of increase of CO2, namely 2 ppmv per year or 2000 ppmv per millennium. You are correct that CO2 has fluctuated in the past; for example the Azolla Event around 49 million years ago witnessed a dramatic decline from 3500 ppmv to 600 ppmv in 800,000 years which supposedly (re)created the polar icecaps, a decline of 3.6 ppmv per millennium. Quite an impact, but much less sudden than our present 2000 ppmv per millennium. If you know of any event prior to 1750 that changed CO2 at anything even remotely like the present rate you have my full attention.

      Bear in mind that we’re burning as much of the planet’s carbon fuel reserves as technology and human ingenuity is allowing us to extract in the past century or so, greatly accelerated in recent decades. This clearly has never been done before by any agent, natural or otherwise—if it had, the fuel would not have been there for us to find and use in recent centuries, since it was only put there once and is not a renewable resource.