Climate of Our Future

Climate Crisis Coalition

The Great Lakes Are Disappearing. By Martin Mittelstaedt, The Toronto Globe and Mail, September 24, 2007. “The Great Lakes… aren’t as great as they used to be. Government forecasters are projecting that Lake Superior, the largest of the five, will fall to its lowest level for September since modern recordkeeping began… The amount flowing out of the lake at its outlet, the St. Mary’s River, has plunged too, and would have to rise by a staggering 50 per cent to reach the average of the past century. Levels on Lakes Michigan and Huron are also sagging, Ontario is down, as is Erie - although the latter, the smallest by volume, has been the least affected. What’s going on? While there is no scientific certainty about what’s ailing the Great Lakes - which together [contain about one-fifth of all the fresh water on the planet and] form the world’s largest interconnected body of fresh water - some fear global warming is at work… Water levels on the Great Lakes go through seasonal fluctuations driven by the flow and ebb of the spring snowmelt. They also experience lengthy… alternating cycles of high and low readings that occur for unknown reasons and can cause levels to vary by a metre or even more over the years… But [this current down cycle] seems much more extreme than usual, lasting for nearly a decade - prompting questions about global warming. Computer model projections generally show that the lakes will shrink as climate changes cause air temperatures around them to rise. Not only will the lakes themselves become warmer, leading them to lose more water to evaporation, but the land is likely to become drier, reducing the supply of groundwater to streams that feed the lakes.” Mittelstaedt points out that while a drop of a meter of water might seem insignificant, about 99 percent of the lake water is non-renewable, a remnant of the last ice age, and only about one percent is replenished each year through precipitation.