The U.S. Senate's leading global warming skeptic has sent letters to several climate change scientists and to the inspectors general of various federal agencies notifying them to retain breached documents and e-mails that he says prove researchers are manipulating data to make the case for global warming.

The move by Oklahoma Sen. James Inhofe, the top Republican on the Environment and Public Works Committee, is part of his push for an investigation into whether the U.N's Intergovernmental Panel on Climate Change has fudged the science on global warming.

The controversy began a week before President Obama announced his decision to go to Copenhagen next month to outline the U.S. goals for reducing greenhouse gas emissions.

It also underscores the difficulty the U.S. faces in achieving a global treaty on emissions reduction at the conference -- one that would replace the Kyoto Protocol from 1997 that the U.S. never ratified.

Inhofe said the manipulation of climate change data has been going on for a long time, but the disclosure of the breached e-mails could bury the climate change legislation that narrowly passed in the House but is stuck in the Senate.

"Now that this has come out and if you go back and look at the speech I made on the Senate floor four years ago, this really just documents what I suspected at the time," Inhofe told Fox News on Tuesday.

Last week, hackers reportedly broke into the electronic files of the Climatic Research Unit of the University of East Anglia in Great Britain, and posted e-mails in which scientists dismissed climate change skeptics, expressed concern about the lack of evidence to prove the threat of global warming, and discussed ways to manipulate the data.

In one e-mail, published in The Washington Post, a scientist wrote, "We can't account for the lack of warming at the moment and it is a travesty that we can't."

In another e-mail, published in the Wall Street Journal, a scientist wrote, "I'm really sorry that you have to go through all this stuff, Phil. Next time I see Pat Michaels at a scientific meeting, I'll be tempted to beat the crap out of him. Very tempted."

Michaels, a senior fellow in environmental studies at the libertarian Cato Institute, has written a number of books forcefully challenging the science of global warming.

In another e-mail, published in the Guardian, a British newspaper, a scientist wrote, "I've just completed Mike's nature (the Science Journal) trick of adding in the real temps to face each series for the last 20 years (from 1981 onwards) and from 1961 for Keith's to hide the decline."

Kevin Trenberth, one of the scientists whose e-mails were hacked, called the breach an "illegal act" and said the e-mails don't undermine the data proving the threat of global warming.

"There's certainly disputes among scientists and how to deal with the skeptics and so on, but not about the science itself," he told Fox News. "And it's not dependent upon a few individuals. There are hundreds of scientists involved around the world that are doing climate change science."

But Myron Ebell of the Competitive Enterprise Institute, said there is no evidence that the e-mails were hacked, and they could have been released by a whistleblower. He also said while Trenberth is not one of the "main gang leaders," he is part of a "gang" that is cooking that data on global warming.

"They've been doing this for years and it's clear by looking at the data files that they have been doing that," he told Fox News. "I'm sorry but these people have already been revealed as not having any honor. Now they're being revealed as not having any sense of shame. They're just trying to brazen it out."