Antarctic Sat. Reconstruction Without Peninsula – Still no Sat. Data
Posted by Jeff Id on February 23, 2009
Just a short post this morning to show one of the different calculations I’ve done. I shouldn’t keep everything to myself after all. The graph below represents a regridding of the Antarctic as presented by Jeff C who was kind enough to send me his data.
I used RegEM to reconstruct the trends without grids A,B,C or D which represent the peninsula of the surface station data along with the 3 pc’s of the original satellite data. This isn’t a perfect reconstruction of the no peninsula data because the 3 pc curves were allegedly derived from the missing satellite data for the complete antarctic. These pc’s would of course have information from the peninsula incorporated in them but since the peninsula is basically an ocean air temperature, this should take us a step closer to the actual arctic surface trend.
PC3 on the left was the original PC from Steig09 with a large number of peninsula surface stations, the one on the right is the no peninsula version. While the right side certainly looks more reasonable, the pre1982 variance went appears larger than the instrument data.
The total trend changed from the original paper of 0.012C/yr to the regridded version of 0.007 to the regridded no peninsula of 0.005 C/yr but is still positive. I couldn’t get the Antarctic area plot to cut the peninsula cleanly this morning before work but the trend across the Antarctic is largely positive and what I would call ‘relatively uniform’ as shown in the original reconstructions. However, this is the reconstructed trend.
Again, because we don’t have the original satellite data or code we cannot complete a true analysis of the original result or the no peninsula data. Simply clipping the gridded satellite data (which is a combination of 3 pcs) will have no effect on the above reconstruction so without the satellite data (and code) we cannot determine the effect of the peninsula on the Steig09 reconstructions. This simply represents a step closer to the no peninsula result.
The AWS reconstruction is IMO nearly meaningless due to lack of data. The 3rd pc of the original paper is completely unnatural, so we are left right where we started from — not knowing if the claimed Antarctic warming is real or not.
The witholding of the single piece of data and code which could resolve this issue is not the best PR move on their part.