Climate change as a driver of change in the Great Lakes St. Lawrence River Basin

• The region saw warmer temperatures, more extreme rain events, and reduced ice cover.
• Average annual temperature is projected to be 1–3 °C warmer by 2063.
• By 2063, intense precipitation events are likely to increase.
• A sustainable future requires mitigation plans such as conservation and a carbon market.
• Immediate adaptation methods include improving energy efficiency and infrastructure.

Climate change in the Great Lakes–St. Lawrence River basin is affecting the socio-ecological system, including the residents who depend on the basin for drinking water, energy, and commerce. Over the past 50 years, air temperatures increased and heavier precipitation events became more frequent, and those trends are projected to continue. Climate change is expected to impact energy supply and demand, governance, and changes in demographics and societal values. More extreme events may exacerbate transport of biological and chemical contaminants and invasive species, and impact lake levels and water quality. We describe historical trends of the regional climate, examine global and regional climate model projections, and explore impacts of climate change with other key drivers of change defined by the Great Lakes Futures Project. Because reducing climate-related damages and economic losses is crucial; we offer three plausible future scenarios of mitigation and adaptation plans. Recommendations to reach a future Utopian scenario require immediate actions, such as improvements in energy conservation, efficiency and generation, curbs to emissions, preventative infrastructure upgrades, and investments in maintaining and monitoring a healthy ecosystem.