Billionaire Tom Steyer, who has effectively pushed for action on climate change in California, is now setting his sights on Washington D.C. ((Jahi Chikwendiu/The Washington Post) Billionaire Tom Steyer, who has effectively pushed for action on climate change in California, is now setting his sights on Washington D.C. ((Jahi Chikwendiu/The Washington Post)

Billionaire and climate activist Tom Steyer has written an open letter to President Obama, warning him to reject the Keystone XL pipeline or face an organized rebellion from some of his most loyal supporters later this month.

On Friday, Canada’s British Columbia province informed a federal review board it opposes the Enbridge Northern Gateway pipeline, which aims to export crude oil from Canada's oil sand region to Asia via tankers. Since that represents an alternative means for shipping oil to Keystone XL, Steyer wrote that "the last of the arguments for the development of the Keystone Pipeline has collapsed."