An Explanation of A Popular Global Warming Graph

Green curve, UAH (University of Alabama, Huntsville), blue is Hadley Center
Climate Research Unit. Both temperature curves are smoothed.
Black line is unsmoothed CO2 measured at Manua Loa Observatory, Hawaii.
Graph from Dr. Clive Best

The above graph depicts the International Panel on Climate Change’s forecast of carbon dioxide made in 1991, twenty years ago. It has been shown on at least a half dozen blogs this weekend. So, I thought I would explain it in case any of my readers have seen it elsewhere.

Why forecast future levels of carbon dioxide (CO2)? In order to forecast future temperatures due to global warming they had to forecast future concentrations of CO2.

The IPCC forecast a “best” (actually, most likely) trend (solid red line) and a high and low value (dotted red lines). As the above graph shows, even though the CO2 increase has been higher than their “best” forecast, temperatures are not going up. Under the IPCC’s hypothesis — that CO2 directly drives atmospheric temperatures — this should not be able to occur.


By definition, in order to be “science,” there must be a falsifiable hypothesis. So, that brings us to the key question: At what point is the global warming forecast falsified?

I don’t think we are quite to the point where the IPCC’s hypothesis — that CO2 levels are the primary driver of atmospheric temperatures — is falsified. But, we are quickly getting there. As I have said on this blog on numerous occasions, if atmospheric temperatures stay significantly below the IPPC’S temperature forecasts (not shown in this post) another 1-3 years, I believe the IPCC’s global warming forecast will be falsified.

One thought on “An Explanation of A Popular Global Warming Graph

  1. This is why they furiously attack the wiki page on falsifiability. They had to spell out modus tollens in freaking algebra to set it straight.