Six Western states and two Canadian provinces pledged (PDF) Wednesday to work together to cut greenhouse gas emissions 15 percent below 2005 levels by 2020, the San Francisco Chronicle reports. The coalition formed six months ago when the governors of Arizona, California, New Mexico, Oregon and Washington created the Western Climate Initiative partnership. Since then, Utah and Canadian provinces Manitoba and British Columbia have joined the effort.

The goal is similar to California’s landmark legislation AB32, which requires the state to cut its emissions 25 percent by 2020.

Although the coalition represents only about 2.3 percent of global greenhouse gas emissions, officials say achieving its goal could cut 350 million metric tons of carbon dioxide – roughly the same as taking 75.6 million cars off the road.

There are no enforcement mechanisms other than what each state or province requires for itself. The partnership partnership plans to create a blueprint for the proposed cap-and-trade system in the region.