Ontario is the newest member of Western Climate Initiative, which includes Manitoba, British Columbia, Quebec and seven U.S. states. Launched in 2007, the WCI is the largest green partnership working to design a cap and trade system for carbon credits and to reduce greenhouse gas emissions at least 15 percent below 2005 levels by 2020. (Each jurisdiction's targets to be met.) Seventy-five percent of Canada's population lives in Western Climate Initiative member provinces.

Ontario Premier Dalton McGuinty said his province is "proud to be welcomed into this important organization of climate-change leaders."