Recently a friend of the Cornwall Alliance wrote us saying,

I saw a very concerning rise claimed for the Great Lakes surface temps—not tenths of a degree but closer to 10. We worry for first time in my 7 decades about migration into Minnesota of poisonous species, death of favorite tree species, etc.

What are the actual data regarding warming—whether of the air or of the waters—of the Great Lakes area?

For the last 10 years I have been consulting with U.S. grain growing interests, and I use the official NOAA surface thermometer temperatures to monitor the 12 main corn growing states in the U.S., an area that includes Minnesota. Summers (June-July-August) in the Midwest U.S. have seen almost no long-term warming.

Regarding the Great Lakes, long-term measurements of lake water temperatures are hard to come by. In the case of Lake Superior, the water canal temperatures at the hydro power plant in “the Soo” (Sault Ste. Marie) go back many decades.  But air temperatures mostly control water temperatures over the long term, and if we look at the Michigan-average June high temperatures over the last 100 years as analyzed by NOAA (updated through 2020, so far a warm summer), there has been no long- term trend.

If we look at other months and include daily low temperatures, then there is usually a small upward trend.

Invasive species are indeed a problem, but those are from ocean ships from all over the world going into the Great Lakes. (I used to live on the St. Marys River, at the outlet of Lake Superior, and and spent a lot of time watching ship traffic.) I remember them becoming a problem when I lived there in the 1970s, which was a particularly cold period in Michigan.

In short, whatever problems may be occurring whether on Minnesota’s land or in the Great Lakes, in terms of invasive species, the appearance of poisonous species, or the death of some tree species, they’re not driven by warming, whether global or regional.

Featured image courtesy of Sharon Mollerus, Flicker Creative Commons.