9 June, 2010
- Climate & Sustainability Forum
- Moving by Degrees
- Moderator: Kai Ryssdal Host, Marketplace
- Panel: Ben Santer, Michael Mann
Source: Moving by Degrees, Marketplace
I asked Dr. Mann and Dr. Santer about the Iris Hypothesis in order to see what the science says regarding Lindzen's idea. Later in the day Dr. Ben Santer mentioned an excellent way to look at the science between what is well established and ideas that simply are not. "Science is at its core about reproducibility." If the result is reproducible or replicated by multiple scientific organizations or scientists, then it is more acceptable than that which is not. Both Santer and Mann seemed to agree that the Iris Hypothesis did not stand up to scientific scrutiny. Discussion as follows:
Question for Dr. Mann and Dr. Santer: Do we have enough resolution and understanding of the models for the Eocene to reasonably rule out Lindzen's 'Iris Effect'? It was much, much warmer then (Eocene), and Lindzen seems to be proposing the idea that we are not going to warm because of that particular theory, can we, reasonably say that that isn't gonna cut the mustard?
Raise your hand if you know what Eocene or Lindzen was (laughter). Seriously c'mon raise your hand if you know it, alright, somebody? ...Go ahead Mike.
Dr. Michael Mann:
I'd be happy to pass it off to Ben for first (laughter)... alright I'll tackle this one. So Richard Lindzen is a scientist from MIT who has expressed contrarian views about climate change. He's often the go to person when journalists are looking for somebody on the 'quote unquote', other side.
Dr. Michael Mann:
He continues to advance this hypothesis, and it evolves over time, that what we call the climate sensitivity, how much warming we expect for a given increase in CO2 levels, is much lower than what all the other evidence, and all the other scientific groups, seem to find.
And his argument has evolved over time, and in my view, pretty much every idea, thought experiment, he's put out to justify that, when subject to the independent scrutiny of other scientists, has not held up to that scrutiny. I believe we are now seeing that with this so called 'Iris Effect'.
The idea was that clouds will behave in a certain way that sort of acts like a thermostat and prevents the surface from warming as much as it otherwise would. Modeling studies as well as observations that have been used to address that issue by a number of different independent teams of scientists have found that the argument doesn't appear to hold up. Today, as well as during the Eocene for example.
Which was when?
Dr. Michael Mann:
55 million years ago.
The modeler on the panel (to Ben).
Dr. Ben Santer:
I just wanted to add to Mikes very nice explanation there, that science is about facts and testing theories, not about eminence of position, or assertions. Professor Lindzen has, as Mike mentioned, had a number of hypotheses. He's said that the climate sensitivity, as Mike mentioned, is very small, so that the amount of warming that one would get for doubling of pre-industrial levels of carbon dioxide would be very small. There's virtually no support in the science that has been done, either on the modeling side, or the observational side, for that extreme position.
This Iris hypothesis has not been dismissed by the scientific community. It was rigorously examined by many scientists: at the National Center for Atmospheric Research, at the University of Washington; they said well okay, does this hypothesis fit the available data?
The bottom line is, no. It is not a convincing explanation of the available data that we have. And that's how science should work, not by assertion, or eminence of position, but by testing theories and facts.
17 April 2007
Lindzen in Newsweek
Gavin Schmidt and Michael Mann
As part of a much larger discussion on Learning to live with Global Warming in Newsweek recently, the editors gave some space for Richard Lindzen to give his standard 'it's no big deal' opinion. While we disagree, we have no beef with serious discussions of the costs and benefits of various courses of action and on the need for adaption to the climate change that is already locked in.
However, Lindzen's piece is not a serious discussion.
Instead, it is a series of strawman arguments, red-herrings and out and out errors.
Lindzen claims that because we don't know what the ideal temperature of the planet should be, we shouldn't be concerned about global warming. But concern about human-driven climate change is not because this is the most perfect of possible worlds - it is because, whatever it's imperfections, it is the world that society is imperfectly adapted to. Lindzen is well aware that predictions of weather are different from climate predictions (the statistics of weather), yet cheerfully uses popular conflation of the two issues to confuse his readers.
14 February 2006
Richard Lindzen’s HoL testimony
Prof. Richard Lindzen (MIT) is often described as the most respectable of the climate 'skeptics' and is frequently cited in discussions here and elsewhere. Lindzen clearly has many fundamentally important papers under his belt (work on the QBO and basic atmospheric dynamics), and a number of papers that have been much less well received by the community (the 'Iris' effect etc.). Last year, he gave evidence to and answered questions from, a UK House of Lords Committee investigating the economics of climate change, in which he discoursed freely on the science. I'll try here to sort out what he said.
Firstly, it is clear that Lindzen only signs up to the first point of the basic 'consensus' as outlined here previously, that the planet has indeed warmed significantly over the 20th century. While he accepts that CO2 and other greenhouse gases have increased due to human activities, and that this should warm the planet, he does not accept that it is necessarily an important component in the 20th century rise. His preferred option (by process of elimination) appears to be intrinsic variability, but he provides no support for this contention.
In terms of scientific content, his testimony covers a few basic topics: the greenhouse effect, climate sensitivity, aerosol forcing and water vapour feedbacks. We have discussed these topics previously (here, here and here), and so my critique of Lindzen's comments will come as no surprise. He intersperses his comments with references to 'alarmism' which I will get to at the end.
In some ways Lindzen's thinking on the climate change issue has not changed much since 1999, as can be seen in an older rebuttal of his position by Jim Hansen (scroll down to Table 1). However, he does seem to have become convinced that the 20th Century warming is real. What is interesting about the comparison between then and now, is that Hansen made two appeals to the data gathering community to test a) whether water vapour feedbacks can be observed, and b) whether the ocean heat content is increasing in line with the model predictions. It is quite telling that both of these data analyses have since been made and they confirm Hansen's contentions, not Lindzen's.
- 2007/04 realclimate.org lindzen-in-newsweek
- 2006/04 realclimate.org lindzen-point-by-point
- 2006/04 realclimate.org open-thread-on-lindzen-op-ed-in-wsj
- 2006/02 realclimate.org richard-lindzens-hol-testimony