Saturday Pick Points - but mainly Antarctica

Given that it is a common topic to all four of the climate change web sites that I look at on Saturday evenings, let’s start with the paper that made the cover of Nature this week. Two of the contributors to Real Climate are among the authors, and it has led to some debate.

Real Climate gives some explanation as to what is in the paper (which is good for those of us too cheap to pay $32 for a copy of the actual paper). However we can see the abstract, which says, inter alia:

Here we show that significant warming extends well beyond the Antarctic Peninsula to cover most of West Antarctica, an area of warming much larger than previously reported. West Antarctic warming exceeds 0.1 °C per decade over the past 50 years, and is strongest in winter and spring. Although this is partly offset by autumn cooling in East Antarctica, the continent-wide average near-surface temperature trend is positive. Simulations using a general circulation model reproduce the essential features of the spatial pattern and the long-term trend, and we suggest that neither can be attributed directly to increases in the strength of the westerlies. Instead, regional changes in atmospheric circulation and associated changes in sea surface temperature and sea ice are required to explain the enhanced warming in West Antarctica.

Now the cooling in the Eastern Antarctic has previously been explained as having been due to the loss of ozone (as I first heard from one of Dr Hansen’s team at the Houston ASPO meeting). Most of the work on monitoring climate effects has focused on the activities around the Antarctic Peninsula, with the inference of GHG effects coming from the retreat of glaciers in that region. Earlier this was said to have occurred only over the past 50 years, but in the current piece it recognizes that it has been going on longer.

It is well known that it has been warming on the Antarctic Peninsula, probably for the last 100 years (measurements begin at the sub-Antarctic Island of Orcadas in 1901 and show a nearly monotonic warming trend).

The plot does not show that warming started at that point, but only that it has been relatively consistent since.
Average temperatures recorded at the Orcades station near Antarctica over the past hundred years.
What the paper discusses is that, while Eastern Antarctica may have been cooling, Western Antarctica has been warming, and that this is due to warmer air circulation. They also note that while the overall Antarctic ice pack has been growing, that on the Western edge has been reducing.

(The other entry at Real Climate this week deals with the problems that the Sami (the reindeer herders of Northern Scandinavia) are having with, among other things, climate change. Since I spent 3 months up there and woke in the mornings to reindeer feeding outside my window, I would have liked chasing that down – perhaps another day).

Over at Gristmill the story is picked up as evidence of warming, although it notes that the ice in the region is melting from underneath (which would suggest a water cause rather than an air one), And interestingly the one comment on the story includes this quote from a NASA site .

Because the satellite is observing energy radiated from the Earth’s surface, the image shows trends in skin temperatures—temperatures from roughly the top millimeter of the land, sea ice, or sea surface—not air temperatures. Making a long-term record out of data from different sensors is challenging because each sensor has its own quirks and may measure temperatures a bit differently. None of the sensors were in orbit at the same time, so scientists could not compare simultaneous observations from different sensors to make sure each was recording temperatures exactly the same. Instead, the team checked the satellite records against ground-based weather station data to inter-calibrate them and make the 26-year satellite record. The scientists estimate the level of uncertainty in the measurements is between 2-3 degrees Celsius.

It is this correlation between surface instrumentation and the satellite data that is the subject of the paper in question. (But the uncertainty in the data is an interesting number).

Over at Climate Audit they draw attention to an earlier post at Real Climate that states that the Antarctic and the waters around it would stay cold, according to the models. That post was in February 2008. That, in turn has led to discussion not only at CA but also at Science Policy. They then have a bit of fun talking about the way in which the authors of the paper are trying to remain consistent with themselves. They also provide sites that give the full text of the letter in Nature.

Which brings me back to Watt’s Up with That which began coverage of the story by pointing out that there are a significant number of volcanoes in the area that is warming, and then also points out the problems where the change in data is smaller than the error bars in the measurements. In regard to the presence of the volcanoes, the NYT followed up with a question to the author about this and got the following answer:

In addition to coming up with my own answer, I did ask the study’s authors. Eric Steig of the University of Washington replied:
Wow. Strange question.
Volcanoes under the ice can’t affect climate on the surface, 2 miles above!
To amplify that a little bit: The ice sheet covering West Antarctica, including its volcanoes, is about two miles thick. Also, Antarctica’s volcanoes do not appear particularly active at present.
Geothermal heat could be contributing to another phenomenon, the thinning of glaciers. And last year, scientists did report an active volcano in West Antarctica.

The latter reference leads to an earlier paper in Nature, reporting on a volcano that actually did punch its way up to the surface (though 2300 years ago), that contains the following:

Heat from a volcano could still be melting ice and contributing to the thinning and speeding up of the Pine Island Glacier, which passes nearby, but Dr. Vaughan doubted that it could be affecting other glaciers in West Antarctica, which have also thinned in recent years. Most glaciologists, including Dr. Vaughan, say that warmer ocean water is the primary cause.

In a follow-up post Anthony quotes a letter that he received from Ross Hays who works for NASA and has extensive experience in the Antarctic. Ross states that the conclusions drawn in the paper are wrong, and gives some anecdotal information on the cooling that he has seen. (Vehicles able to drive on ice sheets that didn’t previously exist as an example).

At the end of the week he notes that snow has fallen in the United Arab Emirates.