Consequences of Regional Climate Change
3.0 CONSEQUENCES OF REGIONAL CLIMATE CHANGE:
OVERVIEW OF POTENTIAL IMPACTS
This section provides a general overview of the potential changes in climate and the associated
effects on ecosystems and human activities within the Great Lakes watershed. Impacts to water
quantity and water quality as well as impacts to quality of life (human health), resource use (e.g.
forestry) and ecosystem health are key sustainability issues for the Great Lakes region.
3.1 APPROACHES FOR THINKING ABOUT FUTURE CHANGES IN CLIMATE
Confident predictions of the future state of the climate are not possible because of the
complexity of the climate system and the social and economic drivers of global change as well
as inherent uncertainties and indeterminacies. Recognizing this, a variety of techniques have
been used to develop Ňclimate scenarios” for climate change impact and adaptation assessments.
Scenarios are developed from global climate models (GCMs), regional climate models (RCMs),
downscaling, analogues (spatial and temporal), and systematic changes to observed climate data.
Numerous resources provide guidance on climate scenario development (Rosenberg et al., 1993;
Wilby and Wigley, 1997; IPCC, 1999; Beersma et al., 2000; CCIS, 2002).
Most climate change impact assessments in the Great Lakes region have used GCM scenarios
(Croley, 1990; Chao, 1999; Mortsch et al., 2000; Lofgren et al., 2002). GCM scenarios are
currently the best tools for understanding the human-caused influence on enhancing the
greenhouse effect. RCMs, when they are available, will be even more useful because of their
smaller scale. Spatial analogues have been used (Mortsch and Quinn, 1996; Croley et al., 1998;
Kunkel et al., 1998). Historical/temporal analogues (usually of extremes) and systematic
changes to climate variables have been used infrequently (Schwartz, 2001). The benefit of these
techniques is that they can explore vulnerability or sensitivity to current climate extremes and
thresholds of changes. These scenarios are described in more detail in Appendix A.
3.2 PROJECTED CHANGES IN CLIMATE
Many attributes of the climate system in the Great Lakes watershed are projected to change.
discussed include:
Key changes
•
Air temperatures increase.
•
Daily air temperature range may decrease.
•
Total annual precipitation increases but precipitation during key seasons
may decrease.
•
More precipitation may fall as rain and less as snow.
•
Intensity of precipitation events may increase.
•
Potential evapotranspiration increases with warmer air temperatures.
33