Perhaps in response to the initial findings of the Berkeley Earth Surface Temperature project and the reported disappointment of some climate skeptics after the lead of the project testified before a Congressional committee, the Wall Street Journal Europe published an article on April 5th (click here for those without a WSJ subscription) by former commodity market statistician Douglas Keenan which questions the significance, in statistical terms, of the warming of the planet over the last century.
With Keenan trying to explain the significance of the global temperature anomaly in terms of a series of coin tosses and the Berkeley project examining billions of pieces of historical temperature data, much (layman) attention now seems to be on the statistical evidence buried in the many collected actual and proxy temperature series, rather than attempting to think about the issue in basic physics terms. This brings me back to a book I read last year by renowned climate scientist James Hansen, titled Storms of My Grandchildren. Hansen clearly and simply explains the notion of the earth’s heat balance and the very subtle changes that humankind is making to it by adding CO2 to the atmosphere. But, as he clearly illustrates, these changes, while small in comparison to the total heat flux of the planet, will lead to very significant long term impacts if left unchecked. He argues that the current shift in heat flux is already greater than the difference between recent glacial and interglacial periods and we know that difference corresponds to some 100 metres of sea level change (over a long period – see chart below).
Therein lies the dilemma of this issue. A simple physics based model using well understood and universally accepted parameters such as Planck’s constant leads to the view that even a small variation in the global heat balance has the potential to shift sea level by many metres. Rather than acting on our understanding of this problem, it has instead sent us rushing to our thermometers to check and see what might actually be happening and whether we can discern a trend upon which we should then act. But waiting for that trend to become blindingly obvious, even to the likes of Douglas Keenan, is folly in itself, given the almost irreversible nature of the build-up of CO2 in the atmosphere and the response of the climate system to the resulting change in surface heat flux.
While examining the temperature record is a vital part of the process, we should also remember that this issue is not one we just happened to stumble across when looking at temperature. There is a clear physical basis for what is going on, identified long before there was any sign of it in current records.