by Judith Curry
Lindzen’s seminar last week that was presented at the House of Commons may be the most effective seminar he has given on Global Warming.
Lets take a closer look at his presentation.
Stated briefly, I will simply try to clarify what the debate over climate change is really about. It most certainly is not about whether climate is changing: it always is. It is not about whether CO2 is increasing: it clearly is. It is not about whether the increase in CO2, by itself, will lead to some warming: it should. The debate is simply over the matter of how much warming the increase in CO2 can lead to, and the connection of such warming to the innumerable claimed catastrophes. The evidence is that the increase in CO2 will lead to very little warming, and that the connection of this minimal warming (or even significant warming) to the purported catastrophes is also minimal. The arguments on which the catastrophic claims are made are extremely weak – and commonly acknowledged as such. They are sometimes overtly dishonest.
JC comment: well I’m sure that got their attention.
From slide 3:
Here are two statements that are completely agreed on by the IPCC. It is crucial to be aware of their implications.
1. A doubling of CO2, by itself, contributes only about 1C to greenhouse warming. All models project more warming, because, within models, there are positive feedbacks from water vapor and clouds, and these feedbacks are considered by the IPCC to be uncertain.
2. If one assumes all warming over the past century is due to anthropogenic greenhouse forcing, then the derived sensitivity of the climate to a doubling of CO2 is less than 1C. The higher sensitivity of existing models is made consistent with observed warming by invoking unknown additional negative forcings from aerosols and solar variability as arbitrary adjustments.
Given the above, the notion that alarming warming is ‘settled science’ should be offensive to any sentient individual, though to be sure, the above is hardly emphasized by the IPCC.
JC comment: #1 is the conventional thinking, although see previous posts on no feedback sensitivity [here and here]. #2 is an oversimplification of how climate sensitivity is determined in the conventional way; for nonconventional thoughts expressed previously at Climate Etc., see [ here and here].
- Carbon Dioxide has been increasing
- There is a greenhouse effect
- There has been a doubling of equivalent CO2 over the past 150 years
- There has very probably been about 0.8 C warming in the past 150 years
- Increasing CO2 alone should cause some warming (about 1C for each doubling)
JC comment: “There has been a doubling of equivalent CO2 over the past 150 years” Not exactly sure what that means, perhaps equivalent means also CH4, etc? This does not seem correct. Also, about 1C for each doubling? Apart from what the no feedback sensitivity actually means, this sensitivity is not linear for multiple doublings of CO2
Unfortunately, denial of the facts on the left, has made the public presentation of the science by those promoting alarm much easier. They merely have to defend the trivially true points on the left; declare that it is only a matter of well- known physics; and relegate the real basis for alarm to a peripheral footnote – even as they slyly acknowledge that this basis is subject to great uncertainty.
JC comment: this is a profound statement
Quite apart from the science itself, there are numerous reasons why an intelligent observer should be suspicious of the presentation of alarm.
- The claim of ‘incontrovertibility.’ Science is never incontrovertible.
- Arguing from ‘authority’ in lieu of scientific reasoning and data or even elementary logic.
- Use of term ‘global warming’ without either definition or quantification.
- Identification of complex phenomena with multiple causes with global warming and even as ‘proof’ of global warming.
- Conflation of existence of climate change with anthropogenic climate change.
JC comment: very good points, althought #4 is not clearly stated
Some Salient Points:
1. Virtually by definition, nothing in science is ‘incontrovertible’ – especially in a primitive and complex field as climate. ‘Incontrovertibility’ belongs to religion where it is referred to as dogma.
2. As noted, the value of ‘authority’ in a primitive and politicized field like climate is of dubious value – it is essential to deal with the science itself. This may present less challenge to the layman than is commonly supposed.
JC comment: generally good points, but I object to the last sentence in #2. Scientists don’t even know how to deal with the complex climate science adequately.
3. ‘Global Warming’ refers to an obscure statistical quantity, globally averaged temperature anomaly, the small residue of far larger and mostly uncorrelated local anomalies. This quantity is highly uncertain, but may be on the order of 0.7C over the past 150 years. This quantity is always varying at this level and there have been periods of both warming and cooling on virtually all time scales. On the time scale of from 1 year to 100 years, there is no need for any externally specified forcing. The climate system is never in equilibrium because, among other things, the ocean transports heat between the surface and the depths. To be sure, however, there are other sources of internal variability as well.
Because the quantity we are speaking of is so small, and the error bars are so large, the quantity is easy to abuse in a variety of ways.
JC comments: good points.
Compares global temperature time series for the periods 1895-1946 with 1957-2008. The trend and variability for the two periods are very similar (which is a strong argument against the unprecedented rate of change), but there is no clear indication that the second period is overall warmer than the first.
Some take away points of the global mean temperature anomaly record:
- Changes are small (order of several tenths of a degree)
- Changes are not causal but rather the residue of regional changes.
- Changes of the order of several tenths of a degree are always present at virtually all time scales.
- Obsessing on the details of this record is more akin to a spectator sport (or tea leaf reading) than a serious contributor to scientific efforts – at least so far.
JC comment: I don’t understand the second bullet? I disagree with the last bullet; the details of the record in terms interannual and decadal variability are of importance to people. The details obviously aren’t useful in supporting or refuting AGW, but proponents then base their arguments on 50 years of data?
4. The claims that the earth has been warming, that there is a greenhouse effect, and that man’s activities have contributed to warming, are trivially true and essentially meaningless in terms of alarm.
Nonetheless, they are frequently trotted out as evidence for alarm.
JC comment: this is the key point, and it isn’t made often enough
Two separate but frequently conflated issues are essential for alarm:
1) The magnitude of warming, and
2) The relation of warming of any magnitude to the projected catastrophe.
When it comes to unusual climate (which always occurs some place), most claims of evidence for global warming are guilty of the ‘prosecutor’s fallacy.’ For example this confuses the near certainty of the fact that if A shoots B, there will be evidence of gunpowder on A’s hand with the assertion that if C has evidence of gunpowder on his hands then C shot B.
However, with global warming the line of argument is even sillier. It generally amounts to something like if A kicked up some dirt, leaving an indentation in the ground into which a rock fell and B tripped on this rock and bumped into C who was carrying a carton of eggs which fell and broke, then if some broken eggs were found it showed that A had kicked up some dirt. These days we go even further, and decide that the best way to prevent broken eggs is to ban dirt kicking.
JC comment: I this is a very effective argument
Where do we go from here?
Given that this has become a quasi-religious issue, it is hard to tell. However, my personal hope is that we will return to normative science, and try to understand how the climate actually behaves. Our present approach of dealing with climate as completely specified by a single number, globally averaged surface temperature anomaly, that is forced by another single number, atmospheric CO2 levels, for example, clearly limits real understanding; so does the replacement of theory by model simulation.
JC comment: I agree with the above statement
In point of fact, there has been progress along these lines and none of it demonstrates a prominent role for CO2. It has been possible to account for the cycle of ice ages simply with orbital variations (as was thought to be the case before global warming mania); tests of sensitivity independent of the assumption that warming is due to CO2 (a circular assumption) show sensitivities lower than models show; the resolution of the early faint sun paradox which could not be resolved by greenhouse gases, is readily resolved by clouds acting as negative feedbacks.
JC comment: above statement reflects more certainty than we actually have, IMO
Lindzen’s view of the science of climate, mostly from the perspective of a simple energy balance and feedback model.
You now have some idea of why I think that there won’t be much warming due to CO2, and without significant global warming, it is impossible to tie catastrophes to such warming. Even with significant warming it would have been extremely difficult to make this connection.
Perhaps we should stop accepting the term, ‘skeptic.’ Skepticism implies doubts about a plausible proposition. Current global warming alarm hardly represents a plausible proposition. Twenty years of repetition and escalation of claims does not make it more plausible. Quite the contrary, the failure to improve the case over 20 years makes the case even less plausible as does the evidence from climategate and other instances of overt cheating.
In the meantime, while I avoid making forecasts for tenths of a degree change in globally averaged temperature anomaly, I am quite willing to state that unprecedented climate catastrophes are not on the horizon though in several thousand years we may return to an ice age.
JC summary: Lindzen’s talk is in two parts. The first part is very effective in pointing out the vacuousness of the defenses of AGW such as the 2010 Science letter signed by 250 members of the NAS and the 2010 letter from Cicerone and Rees.
The second half of the talk is Lindzen’s perspective on the science, which IMO has some good points but is overly simplistic. To Lindzen’s credit, he doesn’t oversell his own perspective (although he seems extremely confident i his own perspective), but states this is “some idea of why I think“. The significance of this is as a “second opinion” and a reasonably well argued perspective, as pointed out in the latest WSJ op-ed (as opposed to appeal to consensus). Lindzen’s perspective is not implausible, as the IPCC perspective is not implausible (in the sense that neither is falsifiable at this point). IMO both the IPCC and Lindzen are overconfident in the assessment of their perspectives; classic “competing certainties”, which means the uncertainty monster is lurking.
The reasons that I think Lindzen’s presentation is so persuasive to public audience are:
1. Lindzen’s persona and appearance, that reeks of scientific gravitas
2. His argument in the first half of the talk is very effective, taking down the public statements by the NAS folk.
3. His scientific argument in the second half of the talk is appealing in that it relies on data and theory (rather than models).
4. Keeping policy and politics out of his scientific argument
JC note: I am currently in Boston, visiting MIT, returning to Atlanta Wed nite. Hence my attention to the blog will be somewhat limited during this period. I will try to moderate the comments on this thread for relevance.