The two divergent visions demonstrate the complexities scientists face as they grapple with the implications of global warming. Great Lakes communities have seen glimpses of both futures. Water levels have been falling again since 1997, approaching the record low since 1860, when people began documenting such changes. But the recent lows, which have already caused headaches, make it plain that a world of consistently low lake levels holds dire implications for commerce, recreation, ecology and water supply. The 1990s produced six of the hottest years ever recorded.
Debate continues over the extent to which human activities have contributed to that warming.
Carbon dioxide, methane, nitrous oxide and other gases have been spewed into the atmosphere in increasing quantities since the Industrial Revolution. By 2100 the average global surface temperature could rise between 1.6 degrees and 6.3 degrees Fahrenheit, some scientists say. Peter Sousounis of the University of Michigan's department of atmospheric, oceanic and space sciences, directed the Great Lakes Regional Assessment, one of several studies across the country that looked at the local impacts of global warming. The assessment will be the backbone of Friday's workshop. The assessment used two computer models of global climate change, along with a third computer model of hydrology in the Great Lakes region, to estimate how global warming might affect the lakes.