Guest post by J Storrs Hall

There are several ways to predict what the temperature trends of the next century will be like. The standard method of prediction in science is to create a theory which embodies a model, test the model experimentally, and then run it into the future for the prediction. There is another way, however, which is simpler in some ways although more complex in others. That’s simply to remember what’s happened before, and assume it will happen again.

Here’s a record of what’s happened before, which most WUWT readers will be familiar with. It’s the GISP2 Greenland ice core record, shown for the Holocene:

I have shamelessly spliced on the instrumental record in red (by setting the temps in 1850 equal); it is the HadSST record.

When I first started looking at GISP2 it seemed to me that there were several places in the record that looked very much like the sharp spike in temperature we’re experiencing now. The obvious thing thing to do seems to be to overlay them for an easy comparison:

Here I’ve plotted the 400 years following each minimum in the record that leads to a sustained sharp rise. There were 10 of them; the first five are plotted in cyan and the more recent 5 in blue. You can see that in the latter part of the Holocene the traces settle down from the wilder swings of the earlier period. Even so, every curve, even the early ones, seems to have an inflection — at least a change in slope — somewhere between 200 and 250 years after the minimum.

The hatched black line is the average of the 5 recent (blue) spikes. The red dots are the uptick at the end of GISP2 and HadSST, spliced at 1850. Note that ALL the minima dates are from GISP2.

Prediction of the 21st century is left to the reader as an exercise.

Read ’em and weep.

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