By Paul Homewood
It is commonly known that the Antarctic Peninsula has seen substantial warming in the last few decades. Jim Steele wrote a guest post for WUWT a couple of days ago, “The Greatest Climate Myths of All”, which contained these observations about Antarctica:
As seen in NASA’s map of regional warming, the Antarctic Peninsula is another unusual “hotspot”, but relative to other climate dynamics, the contribution from CO2 is again not readily apparent. Stronger winds from the positive phase of the Antarctic Oscillation (AAO) increased regional temperatures without adding heat via 2 mechanisms.
First stronger winds from the north reduced sea ice extent by inhibiting the expansion of sea ice along the western Antarctic Peninsula and Amundsen Sea. As in the Arctic, more open water allows larger amounts of stored heat to escape, dramatically raising winter temperatures. Accordingly, during the summer when sea ice is normally absent, there is no steep warming trend.
The eastern side of the Antarctic Peninsula behaves in a contrary manner. There sea ice was not reduced and surface temperatures average 5 to 10° cooler, and the steep winter warming trend was not observed. However there was a significant summer warming trend. Previously during the negative phase of the AAO, weaker winds are typically forced to go around the mountainous peninsula. However the positive AAO generated a wind regime that moved up and over the mountains, creating anomalous foehn storms on the eastern side of the peninsula. As the winds descend, temperatures adiabatically rise 10 to 20 degrees or more due to changes in pressure without any additional heat.
I cannot comment on the science behind this, but I can show how the actual temperature records support what Jim says.
Let’s start with the western side, where we have two long running stations, the two British Antarctic Research stations of Rothera and Faraday.
Rothera 67.34S 68.08W
Faraday 65.15S 64.16W
First, winter temperatures, using GISS data. There is a clear and sizeable upward trend.
And now summer. The trend at Rothera is slightly down, and at Faraday slightly up. (Note, though, the differences in scale to the winter graphs – at Faraday, for instance, we are only looking at a trend of less than half a degree in summer.)
Crossing to the other side of the Peninsula, we find the station of do Marambio on the eastern side.
do Marambio 64.24S 56.62W
In stark contrast to Rothera and Faraday, winter temperatures at the Argentine station of do Marambio are actually declining.
Whilst in summer temperatures are increasing.
The numbers certainly support Jim Steele’s arguments, and suggest that it is regional factors that have led to recent warming there.
Temperature data is from SCAR datasets (Scientific Committee on Antarctic Research), available via GISS.