Climate Change Goings On: Post-Turkey Day

by Bill Chameides | November 29th, 2011
posted by Erica Rowell (Editor)

Permalink | 1 comment

Climate science and politics march on even while most of us were enjoying an extended holiday. Here are two items to take note of.

Another International Confab

The United Nations Framework Convention on Climate Change (UNFCCC), the assembly from whence sprang the Kyoto Protocol, is at it again. This time it’s the 17th conference of the parties (COP 17) in Durban, South Africa. The meetings began yesterday and continue through December 9th.

Last year, along the edges of COP 16 in Mexico City, some incremental progress was made on such issues as deforestation, the establishment of a fund to help poor countries adapt to climate change, and the creation of mechanisms to transition to clean-energy technologies. Countries also reaffirmed a world commitment to avoid dangerous anthropogenic interference with the climate system. However, with the shadow of the debacle of the Copenhagen COP still lingering over the international talks, not to mention a sour economy around the world (and most notably in Europe), expectations for progress on an international deal on climate change at these meetings are exceedingly low.

While much of this year’s discussion will no doubt continue to focus on incremental issues, the elephant in the negotiation rooms will be what, if anything, should be done to fill the vacuum next year when the Kyoto Protocol expires.

On the Science Front, A New Look at Climate Sensitivity

A key parameter in determining how much the climate will be affected by increasing concentrations of greenhouse gases is the so-called climate sensitivity — how much global temperatures increase as a result of a doubling of the concentration of carbon dioxide (CO2) above its preindustrial levels. Best estimates have placed the sensitivity at about 5.4 degrees Fahrenheit (3 degrees Celsius) with a range of 3.6 to 8.1 degrees Fahrenheit (2°C to 4.5°C).

A paper that appeared in the journal Science last week by Andreas Schmittner of Oregon State University and colleagues concludes that the sensitivity is somewhat lower.

The analysis by Schmittner et al was based on estimated climate conditions during the Last Glacial Maximum, some 20,000 years ago during the most recent period of glaciation when CO2 concentrations were only about 185 parts per million. (CO2 today is about 388 ppm; in preindustrial times it was 280 ppm.)

The authors compared temperature reconstructions from that ice age with climate model simulations. They concluded that in order to best simulate the climate of the Last Glacial Maximum, the climate sensitivity is likely to be not 5.4 degrees Fahrenheit, the working temperature scientists have been using, but rather 4.1 degrees Fahrenheit (2.3°C) with a range from 3.1 to 4.7 degrees Fahrenheit (1.7°C to 2.6°C).

Good news if correct, right? It would mean that global temps will be less sensitive to our continued belching of greenhouse gas emissions. And more importantly it would mean that the really rapid and potentially more catastrophic impacts from global warming suggested by climate sensitivities in the 6- to 8-degree Fahrenheit range are less likely. But there are some caveats to note:

  1. There’s been a good deal of coverage in the media about this study — much of it portraying the findings as being a significant departure from what climate scientists have thought previously. Not really. The range of climate sensitivities arrived at by Schmittner et al actually falls within the range previously estimated. And you’ve got to put this study within context. Bear in mind that the working range is based on a number of different approaches, while Schmittner et al’s is based on only one. I’m not ready to adopt Schmittner et al’s lower and narrower sensitivity range without some more independent work.
  2. The authors’ estimate of the climate sensitivity was derived from conditions from the Last Glacial Maximum — a cold period which is opposed to what we’ve got now, a period of warming. Perhaps the climate sensitivity during a glacial period is less than during interglacial or warm periods. More about this at RealClimate.
  3. And regardless, even with Schmittner et al’s results, more emissions mean more warming.

And that last point is why the events at the COP 17 remain quite relevant.

filed under: climate change, faculty, global warming, temperatures
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1 Comment

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  1. MattN
    Dec 4, 2011

    No mention of the thousands of UEA emails leaked the other week from the same source as last time? Not a surprise you failed to mention that….

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