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The lag between temperature and CO2. (Gore’s got it right.)
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) Climate Science
) () Hurricane Spin
Michael Mann and Gavin Schmidt
A recent paper by Vecchi and Soden (preprint) published in the journal Geophysical Research Letters has been widely touted in the news (and some egregiously bad editorials), and the blogosphere as suggesting that increased vertical wind shear associated with tropical circulation changes may offset any tendencies for increased hurricane activity in the tropical Atlantic due to warming oceans. Some have even gone so far as to state that this study proves that recent trends in hurricane activity are part of a natural cycle. Most of this is just ‘spin’ (pun intended), but as usual, the real story is a little more nuanced.
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Ocean Cooling. Not.
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) () A lot has been made of a paper (Lyman et al, 2006) that appeared last year that claimed that the oceans had, contrary to expectation, cooled over the period 2003-2005. At the time, we (correctly) pointed out that this result was going to be hard to reconcile with continued increases in sea level rise (driven in large part by thermal expansion effects), and that there may still be issues with way that the new ARGO floats were being incorporated into the ocean measurement network. Now it seems as if there is a problem in the data and in the latest analysis, the cooling has disappeared.
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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.
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Learning from a simple model
A lot of what gets discussed here in relation to the greenhouse effect is relatively simple, and yet can be confusing to the lay reader. A useful way of demonstrating that simplicity is to use a stripped down mathematical model that is complex enough to include some interesting physics, but simple enough so that you can just write down the answer. This is the staple of most textbooks on the subject, but there are questions that arise in discussions here that don’t ever get addressed in most textbooks. Yet simple models can be useful there too.
I’ll try and cover a few ‘greenhouse’ issues that come up in multiple contexts in the climate debate. Why does ‘radiative forcing’ work as method for comparing different physical impacts on the climate, and why you can’t calculate climate sensitivity just by looking at the surface energy budget. There will be mathematics, but hopefully it won’t be too painful.
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A Tale of Three Interviews
The release of the IPCC Working Group II summary report (on climate change impacts) lead to a large number of stories on climate change in the media and, inevitably, lots of requests for media appearances for climate scientists on the journalists’ Rolodex. On the same day, there was a short article in Science on the ‘framing’ of science communication.
The Science piece, by Scibloggers Chris Mooney and Matt Nisbet, make the point that the way science is expressed in public makes a difference to how it is received. So much, so uncontroversial. However, it generated some trenchant counter–arguments, (and counter–counter–arguments), possibly because they start off criticising a bit of a strawman ‘scientist’ who thinks that ‘if only laypeople better understood technical complexities… controversies would subside’. It’s certainly possible that such people exist, however, they are unlikely to be found among the scientists who are active in trying to communicate to the public. However, instead of arguing about this in a rather abstract way, I thought I’d illustrate the issue by discussing three interviews I did last Thursday and Friday in relation to the IPCC WG II release.
Ozone Hole Leaks and Other Tales
) () Guest commentary by Figen Mekik – Grand Valley State University
“But Figen, humid air feels oppressive, heavy!” students told me, almost in unison. A very treasured moment indeed. I just got a glimpse of probably a long held misconception: water vapor is heavier than dry air. So, we took out our periodic tables and calculators, and went on to calculate the molecular weight of H2O and how it compares to that of N2 and O2 (most of the atmosphere). Happy that I corrected a major fallacy, I didn’t see the rest coming.
Apparently, there are many other sinister fallacies lurking just underneath the surface of the heavy wet air idea. One student asked “is the formula for water vapor the same as for liquid water?” and was astonished to find out that it is always H2O regardless of phase, even in ice! I said “we like to keep things simple in science” and a couple of ladies giggled “as if!”
Then another admitted that he always thought water split into H2 and O2 upon evaporation which would make wet air heavy. Another student answered him with “No way man. When water vapor condenses to liquid, the molecules get bigger which is why liquid water is heavier than vapor.” So we had a long discussion about molecular dynamics of evaporation and condensation. Also, once I helped the students realize the stark contrast between what they think they know (water vapor is heavy) and something else they know from the Weather Channel (low pressure means rain), the cognitive dissonance (the psychological tension created by conflicting knowledge) drove them to question both “bits of knowledge” and to adjust their ideas. By the end of the hour, they were saying this is SOOO weird, humid air rises. Who knew!
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The Sheep Albedo Feedback
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The IPCC sea level numbers
) () The sea level rise numbers published in the new IPCC report (the Fourth Assessment Report, AR4) have already caused considerable confusion. Many media articles and weblogs suggested there is good news on the sea level issue, with future sea level rise expected to be a lot less compared to the previous IPCC report (the Third Assessment Report, TAR). Some articles reported that IPCC had reduced its sea level projection from 88 cm to 59 cm (35 inches to 23 inches) , some even said it was reduced from 88 cm to 43 cm (17 inches), and there were several other versions as well (see “Broad Irony”). These statements are not correct and the new range up to 59 cm is not the full story. Here I will try to clarify what IPCC actually said and how these numbers were derived. (But if you want to skip the details, you can go straight to the critique or the bottom line).
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Does a Global Temperature Exist?
) () Does a global temperature exist? This is the question asked in a recently published article in Journal of Non-Equilibrium Thermodynamics by Christopher Essex, Ross McKitrick, and Bjarne Andresen. The paper argues that the global mean temperature is not physical, and that there may be many other ways of computing a mean which will give different trends.
The common arithmetic mean is just an estimate that provides a measure of the centre value of a batch of measurements (centre of a cloud of data points, and can be written more formally as the integral of x f(x) dx. The whole paper is irrelevant in the context of a climate change because it missed a very central point. CO2 affects all surface temperatures on Earth, and in order to improve the signal-to-noise ratio, an ordinary arithmetic mean will enhance the common signal in all the measurements and suppress the internal variations which are spatially incoherent (e.g. not caused by CO2 or other external forcings). Thus the choice may not need a physical justification, but is part of a scientific test which enables us to get a clearer ‘yes’ or ‘no’. One could choose to look at the global mean sea level instead, which does have a physical meaning because it represents an estimate for the volume of the water in the oceans, but the choice is not crucial as long as the indicator used really responds to the conditions under investigation. And the global mean temperature is indeed a function of the temperature over the whole planetary surface.