A recent comment, here, questions the AGW prediction of polar amplification. He cites a paper by Polyakov et al that he claims shows temperatures in the arctic were warmer than they are now earlier in the 20th century.
[Update: paper is here[PDF]]
I don’t have access to the paper or time to research it well, does anyone else have any comments? My initial impression is that it is about ocean temperatures in one region of the north Atlantic, and I do not trust the numbers he quotes which came from CO2 Science, a site that habitually misrepresents the papers it highlights. But that is hardly enough to base a respectful reply upon.
Regarding the antarctic, I would just point out that the latest studies do indicate some mild warming, not cooling, and sea ice formation is a complicated process, so it is difficult to base firm conclusions on very minor trends. But regardless, models do not anticipate a strong amplification effect there until later. The antarctic is isolated climatically by the circumpolar current in the southern ocean so it will be some time before a dramatic rise is expected on that continent as a whole.
I have a few problems with the models:
First, the models call for polar amplification.
Polyakov shows that the Arctic warming trend is only slightly higher than the Northern Hemisphere trend. He also shows that the Arctic is cooler now than it has been in the 20th century.
Polyakov et al (2003) The composite temperature record shows that since 1875 the Arctic has warmed by 1.2Â°C, so that over the entire record the warming trend was 0.094Â°C decadeâ1, with stronger spring- and wintertime warming. The Arctic temperature trend for the twentieth century (0.05Â°C decadeâ1) was close to the Northern Hemispheric trend (0.06Â°C decadeâ1). The oscillatory behavior of Arctic trends results from incomplete sampling of the large-amplitude LFO. For example, the Arctic temperature was higher in the 1930s-40s than in recent decades, and hence a trend calculated for the period 1920 to the present actually shows cooling. Enhancement of computed trends in recent decades can be partially attributed to the current positive LFO phase.
Serreze realized this problem with the climate models and attempted to show that ice loss would actually start the Polar amplification.
Serreze et al (2006) Rises in surface air temperature (SAT) in response to increasing concentrations of greenhouse gases (GHGs) are expected to be amplified in northern high latitudes, with warming most pronounced over the Arctic Ocean owing to the loss of sea ice. Observations document recent warming, but an enhanced Arctic Ocean signal is not readily evident. This disparity, combined with varying model projections of SAT change, and large variability in observed SAT over the 20th century, may lead one to question the concept of Arctic amplification.
Then we look at the Antarctic. Once again studies show that the Antarctic was the warmest in the 1930-1940s. Further, the Antarctic has been cooling for the last 40 years.
So there is currently no polar amplification. The only way to show one is to cherry pick your start date, as was done for the Antarctic to show warming.
I do not have the time to answer Vernon thoroughly so I appeal to any readers who might be inclined to help out here.
Thanks in advance!