Spatially Weighted Antarctic Temperatures – No Peninsula
Posted by Jeff Id on April 18, 2009
This post is also running with some improvement at WUWT.
From this post and others I’ve determined that the temperature trend in the RegEM versions of the Antarctic are not entirely created by smearing of the peninsula station’s data.
In order to interpret the RegEM results from the previous peninsula free reconstruction, we need to see a baseline reasonable reconstruction without the peninsula. These trends are based entirely on the surface station data. I saw several questions on WUWT about the improved accuracy of satellite temperatures. The satellite temperatures in this paper are of a different type than UAH or RSS use and these are affected substantially by clouds. The result is a much noisier and less trustworthy dataset than surface measurements.
In my opinion this sort of thing is about the best we can do in determining a total trend for the Antarctic over this timeframe. There are a few tweaks which might help but beyond that we have to accept that we don’t know any better than this method shows.
Now removing the peninsula does have basis in science because the ultra thin strip of land is primarily dependent on ocean temperatures and currents. It will be seen as cherry picking because I’ve clipped the part of the Antarctic warming the most. Before TCO or someone points out that I wouldn’t clip it if it didn’t have warming, keep in mind that I show it both with and without the peninsula and I make no claim that clipping the peninsula is the preferred method. It does make some sense though.
First the full trend.
Spatial trends with clipping region shown in black Figure 2.
As I’ve shown before, the trends from 1967 onward.
Spatial distribution 1967 onward.
If I’ve learned anything from all these plots, it’s that the Antarctic isn’t warming at 0.12 +/- 0.7 C/decade. It just isn’t. The actual trend is much lower than that and since 1967 it has even dropped a little across the continent.
Now from the other reconstructions we have the following.
Compared to the 0.12 that Steig et al. cliams the real trends are pretty low. When the peninsula is removed in the properly weighted reconstruciton presented here the trend drops by(0.52-.39)/.52 x100 =25%. This represents a very large contribution to the average simply sbecause this tiny area has shown so much warming. It doesn’t seem reasonable to adjust the continent upward 25% based on this little strip of land.
Surprisingly, in RegEM the trend changes by an similar amount (0.108-0.074).0.08 x100 =31%. This is impressively similar to me as many have speculated that the positive trend in RegEM is created by smearing of peninsula trends. In my spatial reconstruction above, there is no smearing of the peninsula trend at all and there is a 25% trend drop when the peninsula is removed. This means to me that the RegEM high positive trend is not wholly created by the peninsula. Also, this does not mean the trends aren’t smeared by RegEM, they are.