Global warming, and the resulting climate change and extreme weather now appearing worldwide, is arguably the biggest and most challenging threat to the Great Lakes. Scientists agree that there will be ongoing negative impacts from climate change. The climate models show that most of the last century’s warmest years in the region all occurred in the last decade. With this warming trend comes a variety of other effects: warmer water and air temperatures, earlier springs and later falls, less rain and snowfall, more protracted drought-like conditions, flashier storms, longer ice-free periods, and more evaporation.
For the Great Lakes, as huge bodies of open water, with Lake Michigan-Huron being the largest among them in terms of surface area, these changes have serious consequences that are directly linked to the above outlined threats. Ice cover on the Great Lakes during winter has been trending downward over the long-term, with a decline of over 70% over the past 40 years. A full third of the water Georgian Bay loses each year occurs mostly in the winter due to evaporation. When cold prevailing winds sweep from the north or northwest over the warmer water surface, they pick up a lot of moisture, only to drop it again as lake effect snow when they hit land on the other shore or beyond the watershed. Researchers concur that evaporation levels will increase and will outpace any increases in precipitation in the long-term.
If this is the case, which we expect to happen, the effects of climate change will continue to wreak havoc on the Great Lakes and Georgian Bay, impacting water levels, water quality, habitats and biodiversity. Scientists estimate that climate change could lead to the loss of up to 250 cm in water levels, the loss of up to 28% of fish habitat, and wetland losses in certain areas already stressed by loss of habitat.