Since 1997/1998, GISS has been steadily diverging from Had Crut. I have been accused of “cherry picking” this date. In this article I will show that is not the case.
The first plot below shows the ten year running anomaly trend for GISS since 1970. You can think of this as being something like (not exactly) the plot of of the first derivative of the anomaly graph. For example, the 1983 value is almost four. That means that the prior ten year period from 1974-1983 warmed at a rate of almost 4ºC per century. Similarly, the ten year period from 1985-1996 showed no warming trend. The ten year period from 1967-1976 cooled at a rate of about 1ºC per century.
The next graph shows the same thing for Had Crut.
The next graph shows Had Crut (red) overlaid on top of GISS. Note that they were very similar until after 1997.
The next graph shows the same, with areas of divergence colored green. It becomes very clear that there is a change in behaviour after 1997.
The next graph shows the numerical difference between the GISS and Had Crut graphs. There is a clear break starting in 1997. GISS shows a 1ºC higher rate of warming than Had Crut at present.
Reader “Amino” alerted me to this idea. He generated a video showing the same thing using a different approach with 12 year trends.
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