The Sulfate Hypothesis Disproved

Published April 1, 2000

You know the federal climate drill: No, it didn’t warm up as much as we said it would and the reason is that another emission–sulfate aerosols–is “hiding” it. And the amount of compensating cooling just happens to have cancelled out almost all of the predicted warming!

That’s a nice story. But the scientific and popular press have seriously challenged it because of several inconsistencies between the theory and the reality–the most glaring one being that the Southern Hemisphere, largely unaffected by sulfate aerosols, nonetheless refuses to warm as it should.

Sulfate aerosols are largely a byproduct of the combustion of coal in the power generation process–primarily a Northern Hemisphere activity. Without sulfate’s “artificial” cooling, the Southern Hemisphere therefore should be warming with abandon, as the sulfates remain in the atmosphere only five days or so before settling out, far too short a time to allow them to get down there.

Yet every comparison of our truly global satellite records between hemispheres shows that the behavior of the last two decades is opposite what is predicted by the sulfate hypothesis–in fact, the sulfate-rich Northern Hemisphere is warming relative to the sulfate-free Southern Hemisphere. And, as the United Nations’ Intergovernmental Panel on Climate Change noted in its last (1996) full report, if sulfates don’t explain the lack of warming, then it just isn’t going to warm up that much after all.

The National Research Council (NRC) recently admitted the satellite is telling the truth, and that this spells big trouble for the sulfate/greenhouse climate models in their present incarnation. The NRC has attempted to bandage over the gaping hole caused by the discrepancies between model results and observed temperatures. But their efforts have only called more attention to the wound, which may ultimately be fatal to the Kyoto Protocol on climate change.

According to Nature magazine, University of Virginia environmental sciences professor Patrick J. Michaels is probably the nation’s most popular lecturer on the subject of climate change. Michaels is the author of Sound and Fury: The Science and Politics of Global Warming.


Reconciling Observations of Global Temperature Change, 2000. Panel on Reconciling Temperature Observations, National Research Council, National Academy Press, Washington, DC, 85pp.

Houghton, J.T., et al. (editors), 1996. Climate Change 1995: The Science of Climate Change, Intergovernmental Panel on Climate Change, Cambridge University Press, New York, NY, 572pp.