The U.S. Environmental Protection Agency defines climate change as any significant change in the measures of climate (such as temperature, precipitation, or wind patterns) that lasts for an extended period of time (decades or more). The 2007 IPCC Report estimates global average temperatures to increase by 1.1 to 6.4 degress C (2.0-11.5 degrees F) by the end of the 21st century and ocean levels to rise by 18 to 59 cm (7-23 inches). While the specific impacts of these changes will vary by location, climate change will bring more erratic weather patterns and more extreme weather events.
The complexity of the climate change issue makes it difficult to predict exactly how the Great Lakes ecosystem will respond. However, scientists do anticipate that air and water temperatures, evaporation rates, ice cover, seasonal precipitation, and water levels will change. These will all have significant consequences for biota and the ecosystem. Changes in temperature, water level, and weather patterns are complex and inter-related, and they may impact the biology of each lake in different ways.
The GLEAM project assesses climate change using three stressor layers.