Many large corporations are saying one thing and doing another on climate change, the Union of Concerned Scientists found in a study released Wednesday.

The group examined the role that 28 publicly-traded companies played in two significant efforts to address climate change: the EPA’s finding that greenhouse gases endanger public health, and the 2010 ballot initiative in California to suspend the state’s own climate law. (Here are links to the executive summary [1] and the full report [2]).

UCS found that many oil and electric companies were actively engaged in efforts to obstruct climate policy. Chesapeake Energy, Tesoro, Murphy Oil, Occidental Petroleum, Valero Energy, and Peabody Energy were consistently opposed to dealing with climate change: both their PR and their actions worked against new, science-based laws to cut greenhouse gases.

Other companies were less straightforward about their positions. ExxonMobil put out corporate PR that was positive about climate policy while engaging in actions that undermined efforts to deal with climate change. For example, its contributions to anti-climate-action lawmakers outweighed contributions to pro-climate-action lawmakers by a ratio of 10 to 1.

ConocoPhillips, another oil giant, touted on its website that it ‘recognizes that human activity