Nevertheless, Exxon, the world's largest publicly traded company, cut its donations to these groups by more than 40 percent from 2005.
The company still funds about 40 "skeptic groups," according to the report from Greenpeace, but Exxon disputed that many of the organizations were "global warming deniers."
The groups listed include: the American Enterprise Institute, the Cato Institute, the Heritage Foundation, and the National Black Chamber of Commerce. Many of them concern themselves with a wide range of issues.
Earlier this year, Exxon said it had stopped funding a handful of groups, including the Competitive Enterprise Institute, that have downplayed the risks of carbon dioxide emissions.
Exxon has argued that its position on global warming has been widely misunderstood and has taken part in industry talks on greenhouse gas emission regulations.
"We believe that climate change is a serious issue and that action is warranted now," said Exxon Mobil spokesman Dave Gardner.
Gardner said in a statement that the company supports numerous public policy organizations on a variety of topics that do not represent Exxon or speak on its behalf.
"The groups Greenpeace cites are a widely varied group and to classify them as 'climate deniers' is wrong," he said, adding most of the groups had taken no position on climate change.
Still, the Greenpeace report is already receiving scrutiny in Washington, where Rep. Brad Miller, a North Carolina Democrat, has joined the environmentalist group in calling for Exxon to release its plans for contributions during the current year.
"The support of climate skeptics, many of whom have no real grounding in climate science, appears to be an effort to distort public discussion about global warming," Miller said. "So long as popular discussion could be about whether warming was occurring or not, so long as doubt was widespread, consensus for action could be postponed."
Margo Thorning, chief economist of the American Council for Capital Formation said she took "strong exception" with Greenpeace's classification of the group.
"If Greenpeace would take the time to examine the testimony I've given over the years, we've always said that climate change is a problem," Thorning said of her group, which says on its Web site that it promotes economic and environmental policies that promote economic growth.
"We're not climate deniers, we're problem solvers," she said.
Harry Alford, president and CEO of the National Black Chamber of Commerce, said his group believes that there has been a change to the climate, but that the cause is still uncertain.
"Whether its cyclical -- something that happens every few hundred years -- or whatever, I don't know. I don't believe anyone has the answer yet," said Alford, head of the group that says on its Web site it is dedicated to economically empowering African-American communities.
"I think where Greenpeace gets upset is that we don't agree with them. But so what? I think their position is pretty radical and one-sided," he said.
Greenpeace said it included groups that either tried to mischaracterized the science behind global warming or "obstruct the policy debate."
Spokesman Kert Davies said these arguments "hinged on the fact that this (global warming) is not an urgent problem or has no basis. Ultimately, it always boils down to, 'There is no problem, so why would you destroy the economy to solve it."'
Exxon Mobil's spending on the groups was less than a third of the company's $6.5 million in contributions for policy research.
The company and its foundations donated a total of $138.6 million to non-profit organizations and social projects worldwide in 2006.
According to the Greenpeace report, Exxon's spending was well below the nearly $3.6 million it spent on "denial groups" in 2005 and just over half the $3.9 million it shelled out in 2004.