January 30, 2009

Antarctica Again

Filed under: Antarctic, Polar

We have reported on many occasions about the climate history of Antarctica, basically concluding that the frozen continent was not warming up during the most recent couple of decades, despite expectations that it should have been.

At first glance, a new paper by the University of Washington’s Eric Steig and colleagues, published in last week’s Nature magazine and featured as its cover story, may seem to challenge our understanding—at least that is how it was spun to the press (see here and here, for example).

But a closer look at what the paper really says—as opposed to what is said about the paper—shows that there is not much in need of changing with the current understanding of Antarctica’s temperature history.

We’ll show you why.

The temperature history for two large subregions of Antarctica, as derived by Steig et al. (2009), is shown as Figure 1—to get an idea of the history of all of Antarctica, try to visually combine the two panels in Figure 1, giving more weight to the much larger East Antarctica (top panel) (you have to do it visually, because, for some reason, Steig et al., did not provide the history for the full continent in the paper) [Update: We found a compilation for the entire continent over at RealClimate, see Figure 1b] Now, keeping that visual combination in mind, compare it to two other recent derivations of Antarctica’s temperature history (which used different techniques than Steig et al. for determining the temperature history of the sparsely instrumented continent)—Figure 2 is from Monaghan et al. (2008) and Figure 3 is from Chapman and Walsh (2007). Notice much different? Not really.

Figure 1. Temperature history of East Antarctica (top) and West Antarctica (bottom), 1957-2006 as derived according to the methodology of Steig et al. (2009) (figure source: Steig et al, 2009).

Figure 1b. Temperature history of Antarctica, 1957-2006 as derived according to the methodology of Steig et al. (2009) (figure source: RealClimate).

Figure 2. Temperature history of Antarctica, 1950-2005 as derived according to the methodology of Monaghan et al. (2008) (figure source: Monaghan et al., 2008).

Figure 3. Temperature history of Antarctica, 1958-2002 as derived according to the methodology of Chapman and Walsh (2007) (figure source: Chapman and Walsh, 2007).

Over the long-term, that is, since 1957 when the first continuous temperature records from Antarctica began, all three records show that there is a warming tendency (the magnitude of the warming differs between the three papers, with the Steig et al. derivation showing the most). Also notice that over the most recent several decades (since the early 1970s) all three show that there has been little net change—basically the vast majority of the long-term warming in Antarctica took place from the late 1950s to the early 1970s.

This is hardly news. In fact, in our very first World Climate-type publication, released back in 1995, in an article titled “Antarctic Warming: New Old News” we discussed the day’s hot news that Antarctica was warming —and put the warming in perspective—all of it occurring prior to the early 1970s.

Clearly, not much as changed in the past 14 years—it still makes headlines that “Antarctica is warming!” when in fact, the temperature averaged over the entire continent (using whichever methodology you prefer) hasn’t changed much in more than three decades.

If you are interested in why this latest pronouncement has gained so much attention (from both sides of the debate), very interesting articles can be found at RealClimate, MasterResource, and Prometheus. Each provides a unique take on the situation.

Chapman, W.L. and J.E. Walsh. 2007. A Synthesis of Antarctic Temperatures. Journal of Climate, 20, 4096-4117.

Monaghan, A. J., D. H. Bromwich, W. Chapman, and J. C. Comiso (2008), Recent variability and trends of Antarctic near-surface temperature, Journal of Geophysical Research, 113, D04105, doi:10.1029/2007JD009094.

Steig, E. J., et al., 2009. Warming of the Antarctic ice-sheet surface since the 1957 International Geophysical Year. Nature, 457, 459-463.

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