Great Lakes and Global Warming
Global warming could lower water levels in Lake Michigan and Lake Huron by 5 feet over the next century, according to new data generated for a United Nations study of climate change. Such a change would disrupt the Great Lakes shipping industry and threaten the lakes' lucrative sport fishery.
Higher air temperatures could eliminate nearly all winter ice cover on the Great Lakes in the coming decades, which would increase evaporation of the lakes' water. The study is a follow-up to a U.N. report released that said human activities over the past century have caused global warming.
Most scientists agree that global warming will drive down Great Lakes water levels. But it is possible that increased precipitation in the region, another expected symptom of global warming, could temper the lowering of lake levels.
A 5-foot drop in Lake Michigan water levels would widen beaches by about 100 feet. That would benefit shoreline property owners but cause nightmares for freighter captains and recreational boaters, who would be forced to navigate dangerously shallow waters.
A dramatic change in lake levels would require freighters to reduce loads by about 23 percent, which would drive up the cost of shipping. The water level in Lake Michigan and Lake Huron currently is 13 inches below average, and Lake Superior is at its lowest water level since 1926, according to government data.
Global warming also could exacerbate the recent trend toward warmer Great Lakes water temperatures. That could hurt cold-water fish species such as lake trout and salmon, the backbone of a $4.5 billion Great Lakes sport fishery.
It is important to remember that predictions of how global warming will affect the Great Lakes are based on long-term climate trends. There could still be periods of brutally cold weather and blizzards during future winters, despite the projected rise in Earth's average surface temperature.
Global warming is expected to increase precipitation in the Great Lakes region over the next century. But the added precipitation would occur primarily during winter and spring, when water levels in the lakes already are at their peak.