by Judith Curry
But since at least 1988, climate scientists have warned that climate change would bring, in general, increased heat waves, more droughts, more sudden downpours, more widespread wildfires and worsening storms. In the United States, those extremes are happening here and now. – Seth Borenstein (AP)
Seth Borenstein has an (AP) article entitled: This U.S. summer is ‘what global warming looks like.‘ He interviewed more than 15 scientists in preparing this article (including me). Here is what some of the scientists had to say:
“This is what global warming looks like at the regional or personal level,” said Jonathan Overpeck, professor of geosciences and atmospheric sciences at the University of Arizona. “The extra heat increases the odds of worse heat waves, droughts, storms and wildfire. This is certainly what I and many other climate scientists have been warning about.”
Kevin Trenberth, head of climate analysis at the National Center for Atmospheric Research in fire-charred Colorado, said these are the very record-breaking conditions he has said would happen, but many people wouldn’t listen. So it’s I told-you-so time, he said.
As recently as March, a special report an extreme events and disasters by the Nobel Prize-winning Intergovernmental Panel on Climate Change warned of “unprecedented extreme weather and climate events.” Its lead author, Chris Field of the Carnegie Institution and Stanford University, said Monday, “It’s really dramatic how many of the patterns that we’ve talked about as the expression of the extremes are hitting the U.S. right now.”
“What we’re seeing really is a window into what global warming really looks like,” said Princeton University geosciences and international affairs professor Michael Oppenheimer. “It looks like heat. It looks like fires. It looks like this kind of environmental disasters.”
Oppenheimer said that on Thursday. That was before the East Coast was hit with triple-digit temperatures and before a derecho – an unusually strong, long-lived and large straight-line wind storm – blew through Chicago to Washington. The storm and its aftermath killed more than 20 people and left millions without electricity. Experts say it had energy readings five times that of normal thunderstorms.
Fueled by the record high heat, this was one of the most powerful of this type of storm in the region in recent history, said research meteorologist Harold Brooks of the National Severe Storm Laboratory in Norman, Okla. Scientists expect “non-tornadic wind events” like this one and other thunderstorms to increase with climate change because of the heat and instability, he said.
Such patterns haven’t happened only in the past week or two. The spring and winter in the U.S. were the warmest on record and among the least snowy, setting the stage for the weather extremes to come, scientists say.
Since Jan. 1, the United States has set more than 40,000 hot temperature records, but fewer than 6,000 cold temperature records, according to the National Oceanic and Atmospheric Administration. Through most of last century, the U.S. used to set cold and hot records evenly, but in the first decade of this century America set two hot records for every cold one, said Jerry Meehl, a climate extreme expert at the National Center for Atmospheric Research. This year the ratio is about 7 hot to 1 cold. Some computer models say that ratio will hit 20-to-1 by midcentury, Meehl said.
“In the future you would expect larger, longer more intense heat waves and we’ve seen that in the last few summers,” NOAA Climate Monitoring chief Derek Arndt said.
The 100-degree heat, drought, early snowpack melt and beetles waking from hibernation early to strip trees all combined to set the stage for the current unusual spread of wildfires in the West, said University of Montana ecosystems professor Steven Running, an expert on wildfires.
While at least 15 climate scientists told The Associated Press that this long hot U.S. summer is consistent with what is to be expected in global warming, history is full of such extremes, said John Christy at the University of Alabama in Huntsville. He’s a global warming skeptic who says, “The guilty party in my view is Mother Nature.”
But the vast majority of mainstream climate scientists, such as Meehl, disagree: “This is what global warming is like, and we’ll see more of this as we go into the future.”
SB: So might call this an I told you so moment? What do you think?
JC: Extreme events definitely focus people’s attention on climate change, and a local heat wave can certainly do this. By the same token, the cold snow winter of 2010/2011 made people question greenhouse warming. Also, think Hurricane Katrina, which was another focusing event in the US for global warming
SB: What about natural variability? Are other scientists just making too much of what is normal weather variability?
JC: We saw these kinds of heat waves in the 1930’s, and those were definitely not caused by greenhouse gases. Weather variability changes on multidecadal time scales, associated with the large ocean oscillations. I don’t think that what we are seeing this summer is outside the range of natural variability for the past century. In terms of heat waves, particularly in cities, urbanization can also contribute to the warming (the so-called urban heat island effect).
Well, the good news on this one is that no one(?) is trying to attribute this heat wave to global warming. Here is what the recent IPCC Special Report on Extreme Events (discussed previously on this thread) has this to say about heat waves:
In many (but not all) regions over the globe with sufficient data, there is medium confidence that the length or number of warm spells or heat waves has increased.
News bulletin: heat waves happen, when meteorological blocking patterns are set up. There is no linkage between blocking patterns and AGW that I am aware of. I suspect that there may be blocking pattern linkages with the multidecadal climate regimes (e.g. PDO, AMO); I wrote a proposal a few years ago on this but it didn’t get funded.
CFAN Forecast Synopsis – Heat Waves
Here is a freebie, CFAN‘s latest monthly outlook for the U.S.:
Synopsis – The big story during the month of July will be the persistence of temperatures well-above (4-8F) normal stretching from the Midwest through the lower Mississippi River valley. Although temperatures are forecast to moderate for the period 7/9 – 7/11, a second heat wave is forecast to build into the Midwest by the end of Week 2 and last through at least Week 3.
Coastal populated regions of the Northeast are forecast to reach near the triple digits by this weekend but should see more seasonal temperatures by the end of Week 1. During Week 2, warmer than normal temperatures (2-4F) are forecast to build into the Northeast, and these above normal conditions may last through Week 3. In the Northwest, warmer than normal temperatures are forecast to develop by the end of Week 1 and should reach their peak value of 4-8F above normal during the period 7/12 – 7/16.
Weak tropical climate patterns remain in place, suggesting lower than normal forecast confidence beyond Week 2 for most regions of the U.S. However, forecast confidence continues to be higher than normal in the Midwest and Southeast due to the expected persistence of large-scale blocking patterns across the Central U.S.
JC summary: So is this what global warming looks like? Well, this is what the 1930’s and 1950’s looked like. I have stated many times before that I think the 1950’s (warm AMO, cool PDO) are a good analogue for current weather patterns and extreme events. The good news in this latest episode is that no one seems to be trying to attribute extreme events to AGW; merely saying ‘this is what global warming looks like.