How GISS Temperatures Are Diverging From RSS

By Paul Homewood  A guest post earlier today by David Dohbro, comparing satellite and surface temperature datasets, appears to have attracted a certain amount of criticism, not least because it has tried to compare anomalies based on different baselines. This is an update to that analysis.

To get around this issue, I am posting a comparison of GISS surface temperatures and RSS satellite numbers, both based on a baseline of 1979-98, which is the one used by RSS. (GISS still use 1951-80).

This change of baseline means that all GISS temperatures anomalies are reduced by 0.28C.

The graph below shows the GISS minus RSS temperature anomalies from January 1979, the start of the satellite record, to April 2014. I have not shown individual months, as monthly variations can be quite large, and would simply serve to muddy the waters. Instead, I have shown the 12-Month average of the differences.

There are some marked ups and downs in the record up to about 1995. This may be due to early inaccuracies in the satellite dataset, though this would be pure speculation on my part.

Since then, though, certain patterns emerge:

1) During the major El Ninos of 1998 and 2010, RSS temperatures spike to higher levels than GISS. In other words, GISS minus RSS goes negative.

2) There was a period of a few years after 1998, when the two datasets ran closely together.

3) From around 2004, though, there has been a distinct and growing divergence, with GISS showing relatively more warming.

4) Over the full period, as the graph shows, there is a trend is towards greater warming on GISS.

It is also worth noting that the April 2014 temperature anomalies, based on the same 1979-1998 baseline, are as follows:

In other words, GISS are currently showing 0.20C more warming than RSS. This is a significant number, being nearly half of the observed warming, as measured against the 1979-98 average.

The purpose of this post is not to point the finger, and say that one or the other dataset is wrong. Nevertheless, I believe that the differences observed raise serious questions about the accuracy of our global temperature measurements.

See the original Dohbro post

Sources

1) GISS –

http://data.giss.nasa.gov/gistemp/tabledata_v3/GLB.Ts+dSST.txt

2) RSS

http://data.remss.com/msu/monthly_time_series/RSS_Monthly_MSU_AMSU_Channel_TLT_Anomalies_Land_and_Ocean_v03_3.txt