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Great Lakes Ice Cover
Volume 6, Number 16: 16 April 2003

A few days ago, we came across a news report from the Minneapolis-St. Paul Star Tribune entitled "Greenhouse effect may make Minnesota into Kansas."  As the former of these states had been home to several generations of our ancestors, we were naturally curious to learn about its impending transformation, so we read on.

All sorts of bad things were prophesied.  Hence, we were not surprised to learn that the Union of Concerned Scientists (UCS) had organized the study on which the story was based and had also raised the money for it.  Nevertheless, we went to their web site to learn more.

At the UCS website we were greeted by a press release stating "Global Warming Will Alter Character of Great Lakes Region."  One of the predicted changes that caught our collective eye was the claim there would be less winter ice cover of the lakes within the region as the area warmed.  Turning to the actual report upon which the press release was based (Kling et al., 2003), we found this was indeed what was predicted, although with respect to recorded reality, the authors stated that "in the Great Lakes themselves, the extent of ice cover has been highly variable from 1963 to the present with no long-term trend [our italics]."  Nevertheless, they promoted the notion of declining winter ice cover by stating immediately thereafter that "in recent years the Great Lakes have had little ice cover."

Determined to dig a bit deeper into this latter claim, we turned to the study of Assel et al. (2003) -- which was not referenced by Kling et al. -- to see if there was any evidence for this assertion.  For Lakes Michigan, Huron and Ontario, there was none; winter ice cover at the end of the measurement period was essentially the same as it was at the beginning.  Lakes Superior and Erie, on the other hand, did show a bit of a decline in winter ice cover.  However, in the following and most recent winter (2002) -- data for which were not available when the paper of Assel et al. was written but were subsequently reported on the Internet by the Canadian Ice Service -- Lakes Superior and Erie, as well as Lake Huron, experienced 100% ice cover, as noted by Reuters and CBC News on 11 March 2003 and by CNN and the London Free Press News on 12 March 2003.

So how unusual is it for Lakes Superior, Huron and Erie to freeze over completely?  And in the same year?

In carefully inspecting the data presentations of Assel et al., it appears that in addition to 2002, prior complete freeze-overs of Lake Erie occurred in 1998, 1997, 1979, 1978 and 1977.  Lake Superior, on the other hand, froze over completely only twice before, in 1996 and 1979; while Lake Huron never completely froze over during the prior period of time stretching all the way back to 1963.  In addition, the data reveal that only once before have two of these three Great Lakes ever experienced 100% ice cover in the same year (1979); and never before, in the period from 1963 to the present, have all three of them completely frozen over in the same year.

Of course, one incredibly anomalous year does not define a trend.  But it can sure raise havoc with the status quo or any prior weak trend.  Hence, much more data will clearly be required before we can say with any confidence what the long-term future will hold for the climate of the Great Lakes region, although that fact appears to be no impediment to those intent on scaring the people of the world into believing they must act now, and in heroic fashion, to prevent catastrophic consequences.

The senior author of the Union of Concerned Scientists study, for example, is quoted in that organization's press release of 8 April 2003 as saying that the people of the Great Lakes region need to "reduce the amount of fossil fuels [they] burn to produce electricity and drive [their] cars," while another of the authors (a staff scientist for the Union of Concerned Scientists) says that "waiting 10 or more years to reduce emissions will increase the eventual severity, expense, and likelihood of irreversible losses," which, she adds, would be "a terrible legacy to leave our children and grandchildren."

It is amazing that such great ills can be so emotionally projected on the basis of so little firm data.

Sherwood, Keith and Craig Idso

References
Assel, R., Cronk, K. and Norton, D.  2003.  Recent trends in Laurentian Great Lakes ice cover.  Climatic Change 57: 185-204.

Kling, G.W., Hayhoe, K., Johnson, L.B., Magnuson, J.J., Polasky, S., Robinson, S.K., Shuter, B.J., Wander, M.M., Wuebbles, D.J., Zak, D.R., Lindroth, R.L., Moser, S.C. and Wilson, M.L.  2003.  Confronting Climate Change in the Great Lakes Region: Impacts on our Communities and Ecosystems.  Union of Concerned Scientists, Cambridge, MA, and Ecological Society of America, Washington, DC.