A study by Stephen Schwartz of Brookhaven National Lab to be published in the Journal of Geophysical Research (JGR) has the denyers and doubters delighted.
“Overturning the ‘Consensus’ in One Fell Swoop” gloats Planet Gore, which says the study “concludes that the Earth’s climate is only about one-third as sensitive to carbon dioxide as the IPCC assumes” and so we “should expect about a 0.6oC additional increase in temperature between now and 2070″ [0.1oC per decade] if CO2 concentrations hit 550 parts per million, double preindustrial levels.
Is this possible? Aren’t we already warming up 0.2oC per decade — a rate that is expected to rise? Has future global warming been wildly overestimated by the Intergovernmental Panel on Climate Change (IPCC) consensus?
Or, as I argue in my book, has future global warming been underestimated by the IPCC. This is perhaps the central issue in the climate change debate, so this will be a long post. To cut to the chase, it is not possible for one study to overturn the consensus, and in any case this inadequately researched, overly simplistic, and mistake-riddled study certainly doesn’t.
Climate sensitivity expert James Annan points out key mistakes that rip the guts out of Schwartz’s analysis. That is strike one. Now I’ll offer my 2 cents worth.
I have always considered it ironic that the Denyers — who don’t believe the consensus, which is based on hundreds of studies that they obviously reject out of hand — are so enamored of the very few studies that suggest the consensus overestimates climate change (while ignoring the great many studies that suggest an underestimate). Even more ironic, let me quote from the end of the Schwartz paper, which is painfully aware how dubious its main conclusion is:
Finally, as the present analysis rests on a simple single-compartment energy balance model, the question must inevitably arise whether the rather obdurate climate system might be amenable to determination of its key properties through empirical analysis based on such a simple model. In response to that question it might have to be said that it remains to be seen. In this context it is hoped that the present study might stimulate further work along these lines with more complex models…. Ultimately of course the climate models are essential to provide much more refined projections of climate change than would be available from the global mean quantities that result from an analysis of the present sort.
Yes, the Denyers routinely attack the IPCC consensus for using elaborate computer models that they claim are still far too simplistic to model the real climate — claiming those models omit key variables and negative feedbacks that would reduce future climate change. But now they would have us embrace a self-acknowledged “simple model” — one far more simplistic than the climate models the Denyers repeatedly denounce as too simplistic. That’s chutzpah.
There is both a simple reason and a more complicated reason why I firmly believe that IPCC scientists are underestimating future climate change (and hence that Schwartz is very wrong). First, the simple reason — Scientists have underestimated current climate change:
So what are the chances that the IPCC has overestimated the climate sensitivity by a factor of three as Schwartz’s overly simple model would have us believe — that the rate of warming in the next several decades will be under half that of the rate of the past 16 years? Zilch. Does Schwartz mention any of these data points? Not one. Shame on the JGR editors for letting this go by. Strike two.
Now on to the more complicated reason I am convinced scientists are underestimating future climate change.