Unfortunately, the anti-science White House has disregarded his expert opinion :

Keystone XL pipeline would have little impact on climate change, State Department analysis says

Keystone XL pipeline would have little impact on climate change, State Department analysis says – The Washington Post

Ignoring an unimpeachable source like James Hansen is surely an impeachable offense for Obama. If Keystone goes through, future generations will have to live without a climate.