ontarioOntario officially joins the Western Climate Initiative as a full partner. Sweet.

Some Americans may not fully realize the significance of this. So for my fellow Yankees (and with apologies to readers north of the border) … Ontario is the California of Canada in the sense that it has more people and economic activity than any other province. On the other hand, Ontario is the Michigan of Canada in the sense that it has a huge auto manufacturing base. And yet Ontario is also the New York of Canada in the sense that it is the seat of the country’s biggest city, major banks, and cultural headquarters. And finally, Ontario is the Washington, D.C. of Canada in the sense that it is home to the nation’s capitol.

So it’s a big deal.

Ontario adds nearly 12.9 million people to the Western Climate Initiative. In combination with British Columbia, Manitoba, and Quebec — already members of WCI — nearly 80 percent of Canada is now under a hard carbon cap. In political terms, this means that prime minister Stephen Harper and the province of Alberta (the Texas of Canada) will now have to go off and play by themselves. It’s a giant poke in the eye to Canada’s lax federal leadership on climate change.

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And it’s terrific news for the WCI states too. Ontario has a GDP comparable to the combined economies of Washington, Oregon, Montana, and Utah. And it means that the WCI is now home to nearly 85 million North Americans.