When President Obama unveiled his program to tackle climate change last month, he deliberately sidestepped Congress as a hopeless bastion of obstruction, relying completely on changes that could be imposed by regulatory agencies. A two-year study by the Investigative Reporting Workshop at American University, released today, illustrates what might be one of the reasons why he had to take this circuitous route. Fossil fuel magnates Charles and David Koch have, through Americans for Prosperity, a conservative group they back, succeeded in persuading many members of Congress to sign a little-known pledge in which they have promised to vote against legislation relating to climate change unless it is accompanied by an equivalent amount of tax cuts. Since most solutions to the problem of greenhouse-gas emissions require costs to the polluters and the public, the pledge essentially commits those who sign to it to vote against nearly any meaningful bill regarding global warning, and acts as yet another roadblock to action.

The investigative study tracks the political influence wielded by the billionaire Koch brothers, who have harnessed part of the fortune generated by their company, Koch Industries, the second largest private corporation in the country, to further their conservative libertarian activism. Charles Lewis, the Executive Editor of the Investigative Reporting Workshop explained that the I.R.W., a non-profit news organization attached to American University, spent two years focussing on Koch Industries because, “There is no other corporation in the U.S. today, in my view, that is as unabashedly, bare-knuckle aggressive across the board about its own self-interest, in the political process, in the nonprofit-policy-advocacy realm, even increasingly in academia and the broader public marketplace of ideas.” Formerly head of the Center for Public Integrity in Washington, Lewis has focussed for years on the way money affects American politics. “The Kochs’ influence, without a doubt, is growing,” he believes. A spokeswoman for the Kochs declined to comment.

In its multi-part report, “The Koch Club,” written by Lewis, Eric Holmberg, Alexia Campbell, and Lydia Beyoud, the Workshop found that between 2007 and 2011 the Kochs donated $41.2 million to ninety tax-exempt organizations promoting the ultra-libertarian policies that the brothers favor—policies that are often highly advantageous to their corporate interests. In addition, during this same period they gave $30.5 million to two hundred and twenty-one colleges and universities, often to fund academic programs advocating their worldview. Among the positions embraced by the Kochs are fewer government regulations on business, lower taxes, and skepticism about the causes and impact of climate change.

Climate-change policy directly affects Koch Industries’s bottom line. Koch Industries, according to Environmental Protection Agency statistics cited in the study, is a major source of carbon-dioxide emissions, the kind of pollution that most scientists believe causes global warming. In 2011, according to the E.P.A.’s greenhouse-gas-reporting database, the company, which has oil refineries in three states, emitted over twenty-four million tons of carbon dioxide, as much as is typically emitted by five million cars.

Starting in 2008, a year after the Supreme Court ruled that the Environmental Protection Agency could regulate greenhouse gasses as a form of pollution, accelerating possible Congressional action on climate change, the Koch-funded nonprofit group, Americans for Prosperity, devised the “No Climate Tax” pledge. It has been, according to the study, a component of a remarkably successful campaign to prevent lawmakers from addressing climate change. Two successive efforts to control greenhouse-gas emissions by implementing cap-and-trade energy bills died in the Senate, the latter of which was specifically targeted by A.F.P.’s pledge. By now, four hundred and eleven current office holders nationwide have signed the pledge. Signatories include the entire Republican leadership in the House of Representatives, a third of the members of the House of Representatives as a whole, and a quarter of U.S. senators.

The 2010 mid-term elections were a high watermark for the pledge. The Kochs, like many other conservative benefactors, gave generously to efforts to help shift the majority in the House of Representatives from Democratic to Republican. Koch Industries’s political action committee spent $1.3 million on congressional campaigns that year. When Republicans did take control of the House, a huge block of climate-change opponents was empowered. Fully one hundred and fifty-six members of the House of Representatives that year had signed the “No Climate Tax Pledge.” Of the eighty-five freshmen Republican congressmen elected to the House of Representatives in 2010, seventy-six had signed the No Climate Tax pledge. Fifty-seven of those received campaign contributions from Koch Industries’s political action committee. The study notes that more than half of the House members who signed the pledge in the 112th Congress made statements doubting climate-change science, despite the fact that there is overwhelming scientific consensus on the subject.

The study recounts that the Kochs have influenced the congressional climate-change debate in other ways, too, which include funding an array of nonprofit groups whose experts have testified in Congress questioning the cause, the severity, and the necessity of, acting on climate change. Since 2007, “Senior staff at more than a dozen Koch-funded nonprofit groups have made frequent trips to testify on Capitol Hill in favor of deregulation,” of the environment and energy sector, the study says.

The No Climate Tax pledge has made inroads at the state level, as well. In just the three states of Missouri, Michigan, and Kansas, where Koch Industries has its headquarters, forty-eight office holders have now signed the pledge. Nationwide, it has penetrated even the most local levels. Signatories now include the Oklahoma superintendent of schools, the Idaho Treasurer, and three justices of the peace in Arkansas.

Lewis concludes that “One of the overarching themes from what we have found is that,” when it comes to blocking action on climate change, “things obviously go better with Koch!”

Due to an editing error, this article originally, and incorrectly, contained quotation marks around a paraphrased description of the pledge; the punctuation has since been corrected.

Photograph by Carlo Allegri/AP.