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Learning from a simple model

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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

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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.

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Ozone Hole Leaks and Other Tales Ozon Deliği Sızdırıyor ve Bunun Gibi Başka Hikayeler

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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 already-reeling "consensus" supposedly linking climate change to CO2 is about to receive its final coup-de-grace from a remarkable new result announced in a press conference today by Dr. Ewe Noh-Watt of the New Zealand Institute of Veterinary Climatology [1]. Noh-Watt and his co-workers, describing work funded by a generous grant from the Veterinary Climate Science Coalition, declared "We have seen the future of climate — and it is Sheep." Prof. Jean-Belliere Poisson d’Avril, star student of Claude Allegro Molto-Troppo (discoverer of the Tropposphere) reacted with the words, "Parbleu! C’est la meilleure chose depuis les baguettes tranchées!"

The hypothesis begins with the simple observation that most sheep are white, and therefore have a higher albedo than the land on which they typically graze (see figure below). This effect is confirmed by the recent Sheep Radiation Budget Experiment. The next step in the chain of logic is to note that the sheep population of New Zealand has plummeted in recent years. The resulting decrease in albedo leads to an increase in absorbed Solar radiation, thus warming the planet. The Sheep Albedo hypothesis draws some inspiration from the earlier work of Squeak and Diddlesworth [2] on the effect of the ptarmigan population on the energy balance of the Laurentide ice sheet. Noh-Watt hastens to emphasize that the two hypotheses are quite distinct, since the species of ptarmigan involved in the Squeak-Diddlesworth effect is now extinct.

Una traducción está disponible aquí
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The IPCC sea level numbers Os números do nível do mar do IPCC

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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?Existe uma temperature global?

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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.

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Has Pacific Northwest snowpack declined? Yes.

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There has been a bit of a flap here at the University of Washington over the state of the snowpack in United States Pacific Northwest region. The Seattle city mayor, Greg Nickels (a well known advocate for city-based CO2 reduction initiatives) wrote in an Op-Ed piece in the Seattle Times that

The average snowpack in the Cascades has declined 50 percent since 1950 and will be cut in half again in 30 years if we don’t start addressing the problems of climate change now. That snow not only provides our drinking water, it powers the hydroelectric dams that keep our lights on.
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Adventures on the East Side Doğu Yakasında Maceralar

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So that was …. interesting.

First off, I’d like to thank the commenters for all of the suggestions and ideas to the previous post. They were certainly useful. In particularly, the connection with the difficulties faced by evolutionists in debates vs. creationists proved to be very a propos. Our side played it it pretty straight – the basic IPCC line (Richard Somerville), commentary on the how ‘scientized’ political debates abuse science (me, though without using the word ‘scientized’!) and the projections and potential solutions (Brenda Ekwurzel). Crichton went with the crowd-pleasing condemnation of private jet-flying liberals – very popular, even among the private jet-flying Eastsiders present) and the apparent hypocrisy of people who think that global warming is a problem using any energy at all. Lindzen used his standard presentation – CO2 will be trivial effect, no one knows anything about aerosols, sensitivity from the 20th Century is tiny, and by the way global warming stopped in 1998. Stott is a bit of a force of nature and essentially accused anyone who thinks global warming is a problem of explicitly rooting for misery and poverty in the third world. He also brought up the whole cosmic ray issue as the next big thing in climate science.
Update: The transcript is now available – though be aware that it has not yet been verified for accuracy. Audio + Podcast.
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Broad Irony

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Michael Mann and Gavin Schmidt

[update 3/20/07: The New York Times has run a short letter from us w/ a link to RealClimate for more info (scroll down to 5th letter; the 2nd letter from James McCarthy of Harvard is quite good too, as are some of the others).]

The first rule when criticizing popular science presentations for inaccuracies should be to double check any ‘facts’ you use. It is rather ironic then that William Broad’s latest piece on Al Gore plays just as loose with them as he accuses Gore of doing.

We criticized William Broad previously (Broadly Misleading) for a piece that misrepresented the scientific understanding of the factors that drive climate change over millions of years, systematically understating the scientifically-established role of greenhouse gases, and over-stating the role of natural factors including those as speculative as cosmic rays (see our recent discussion here). In this piece, Broad attempts to discredit Gore’s “An Inconvenient Truth” by exaggerating the legitimate, but minor, criticisms of his treatment of the science by experts on climate science, and presenting specious or unsubstantiated criticisms by a small number of the usual, well-known contrarians who wouldn’t agree even if Gore read aloud from the latest IPCC report.
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