According to the New York Times:

Lisa P. Jackson is stepping down as administrator of the Environmental Protection Agency after a four-year tenure that began with high hopes of sweeping action to address climate change and other environmental ills but ended with a series of rear-guard actions to defend the agency against challenges from industry, Republicans in Congress and, at times, the Obama White House.

Jackson did succeed  in having greenhouse gases that cause climate change recognized as pollutants that can be regulated by the EPA.  Read more.