Great Lakes Retrospectives

A Product of the Great Lakes Water Quality Agreement


The Great Lakes Water Quality Agreement (Agreement) is a commitment between the governments of the United States and Canada. First signed in 1972 and most recently amended in 2012, the two countries have coordinated to advance protection and restoration of the Great Lakes for 50 years. Promoting research and advancing the understanding of and communicating about climate change impacts was added to the Agreement with the 2012 amendments as Annex 9: Climate Change Impacts. These retrospective summaries, along with their prospective counterparts, were developed to mark the 50th anniversary of the signing of the Agreement in 1972 and provide an overview of past climate and lake trends for the Great Lakes and surrounding basins. These reports were created through Annex 9: Climate Change Impacts to serve the work being done on the other annexes of the Agreement, in particular the Lakewide Action and Management Plans, and natural resources managers and decision makers across the Great Lakes region.

Historical observations for each retrospective summary were retrieved from the NOAA-Great Lakes Environmental Research Laboratory (GLERL) Great Lakes Monthly Hydrologic Data, Great Lakes Ice Cover Database, and Great Lakes CoastWatch Surface Environmental Analysis, to provide a snapshot of lake level, precipitation, water temperature, and ice trends in the last 50 years.  The 50-year time period of reference is 1972-2021, with the exception of variables that do not have records that far back (ice cover records begin in 1973, water temperature records begin in 1995).

For a more in-depth summary of trends on the Great Lakes, please refer to GLISA’s Sustained Assessment of the Great Lakes Resource.

Click one of the lakes below to be taken to its Retrospective summary.

Lake Superior
Lake Michigan
Lake Huron
Lake Erie
Lake Ontario

Acknowledgements These webpages were developed by the GLISA team with funding from National Atmospheric and Atmospheric Administration’s (NOAA) Great Lakes Regional Collaboration Team and Cooperative Institute for Great Lakes Research (CIGLR), and support from an advisory group made up of the following individuals:

  • Alex Cannon, Environment and Climate Change Canada
  • Steve Clement, Environment and Climate Change Canada
  • Jennifer Day, National Oceanic and Atmospheric Administration
  • Jenessa Doherty, Environment and Climate Change Canada
  • John Haugland, Environmental Protection Agency
  • Shaffina Kassam, Environment and Climate Change Canada
  • Doug Kluck, National Oceanic and Atmospheric Administration
  • Sharon Lam, Toronto and Regional Conservation Authority
  • Glenn Milner, Climate Risk Institute
  • Biljana Music, Ouranos
  • Michael Notaro, University of Wisconsin
  • Frank Seglenieks, Environment and Climate Change Canada
  • Ram Yerubandi, Environment and Climate Change Canada

GLISA Contributors

Kim Channell, Omar Gates, and Patrick Britt

If you have questions, comments, or feedback on the Great Lakes Retrospectives, please contact Kim Channell (