Twenty-two percent of the world's fresh surface water

The imperiled Great Lakes take the national stage

According to research by the National Oceanic and Atmospheric Administration and the University of Michigan, average temperatures in the region have risen 2.3 degrees Fahrenheit since 1951. Summer lake surface temperatures have been increasing faster than the surrounding air temperatures, with Lake Superior rising by 4.5 degrees.

When I was a kid we used to swim in that superior lake, Superior. The water was never more than a few degrees above ice. The neighborhood moms would supervise. Their unanimous rule: You have to get out when your lips turn blue. We watched each other's lips. They turned blue. We got out.

Now, I'm not getting in. Last time I waded into a Great Lake I turned around when the water got about ankle deep. I'm not sure another 4.5 degrees would change my mind.

But as far as the ecology of the lakes is concerned, the temperature increase is a very big deal.

(Both political conventions this year are in cities on the shore of Lake Michigan.)