The name of huge oil conglomerate Koch Industries didn’t appear anywhere on the ad the Cato Institute placed in the The Washington Post and other major papers Monday and over the weekend. But the ad — which questioned existing science on climate change — has Koch’s imprint all over it.

The top of the advertisement run by the Cato Institute this week.

Bigger in size than either Microsoft or AT&T, Koch Industries tends to fly under the public radar screen. Yet as the Center has previously reported, Koch — which owns refineries that can process over 800,000 oil barrels a day, and operates some 4,000 miles of pipeline — is a prolific political donor. Today, Koch is the second-largest privately held company in America.

While Koch has a long history of pushing libertarianism through its grant-making, more recently, the company has established itself as an aggressive opponent of climate legislation and a major funder of climate skeptics — including the libertarian Cato Institute.

Co-founded by Charles Koch in 1977, in recent years, the Cato Institute has hosted numerous D.C.-based briefings featuring various climate skeptics. A briefing book Cato distributed among members of the 107th Congress dismissed the Kyoto protocol and further asked, “Is the way the planet warms something that we should even try to stop?”

Though Cato’s funding has diversified since its early days, it’s thanks to Koch that the think-tank exists at all: According to Gregg Easterbrook, in its early years, the "largest portion" of the Cato Institute's bills were paid by Charles Koch.

While Cato takes the battle for public opinion on global warming to the pages of the Post, Koch has conducted a quieter scrimmage behind the scenes. Last year alone Koch Industries spent $7.4 million to lobby Congress on global warming and other issues. Meanwhile as the Center noted in September, in recent years, Koch has stepped up its funding of other global warming skeptic groups as well. From 2004-2006, the Koch Foundation increased such funding to $5.3 million, an increase of 93 percent in just those two years alone.

Some Koch-supported outfits take a less diplomatic tone than the Cato Institute’s latest ad. Founded by David Koch (Charles' brother), for example, Americans for Prosperity — which has launched a major PR blitz around the nation — describes itself as working to “expose the hypocrisy and outrageous economic costs” of “so-called global warming regulations.”

Americans for Prosperity also describes Charles Koch as a “true hero to the free market movement and a proven expert in the science of success.”

Correction: The post originally stated that Koch Industries spent $7.4 million to lobby Congress solely on global warming. The money actually went to lobbying on a variety of issues, of which global warming was one. And to clarify: An article the Center originally posted on Sept. 30, 2008, "Global Warming: Heated Denials," stated that in 2006, the Koch Foundation gave $5.3 million to "global warming skeptic groups." In addition to their global warming-related work, these groups, such as the Pacific Research Institute, the Media Research Center, and the Mercatus Center, are concerned with an array of other issues, including free enterprise, personal responsibility, and health care.