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Saturday, November 23, 2013

Just for Fun - Battle of the Surface Temperature Reconstructions

The Berkeley Earth Surface Temperature (BEST) program supposedly has a "global" combined land and ocean temperature series that is ready but just getting some last minute tweaks and reviews.  I have been looking for it to hit the news but I keep getting tired of waiting.  GISS land and oceans surface temperature appears to have a baseline/seasonal cycle selection issue that I have been wanting to see how much it might impact trends, especially the "pause".

The difference should not be much, less than the stated error margin, which normally would be no big deal.  Since climate change is a political hot potato though it seems every milliKelvin is a battle ground.  So I built my own simple "Global" surface temperture record using the full baseline and seasonal cycle for periods where both hemisphere actually had data. 

Tah dah!  As advertised there is not much difference since GISS loti uses the same "global" ocean data ERSSTv3b and what difference there is is mainly near the end where long range interpolation used by GISS might tend to over emphasis Arctic Winter Warming.  BEST uses kriging which should be more reliable than simple interpolation provided you avoid using unicorns in the sky for a reference.

In a previous post I showed how the inclusion of the Antarctic data had added to the variance of the southern hemisphere.

I had also shown the difference in the northern hemisphere which I suspected was due to Arctic Winter Warming.  So now I have just upped the accuracy a tiny bit by removing the seasonal cycle from both the land BEST and ocean ERSSTv3b data an baselined to the entire period which is supposed to be the way it should be done.  This kind of sucks though because every year the entire reconstruction would need to be adjusted to the newer, longer baseline. 

Since I used the actual temperatures instead of anomaly I also have a "global" land and ocean diurnatal temperature range.

And there is the "Global" Tmax and Tmin with all its seasonal cycle glory. 

While I am pretty sure that my reconstruction is pretty close, it depends on the current actual land/ocean ratio and mine is pretty old, it would be Best to wait for BEST before screaming that GISS might be off by 0.05 C.

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