Ward objected to an Exxon Corporate Citizenship document that described "gaps in the science" of climate change, casting doubt on the link between global warming and the greenhouse gases which humans produce by burning fossil fuels.

Exxon has said there were such gaps in the latest report of the United Nations' Intergovernmental Panel on Climate Change (IPCC), published in 2001, which had used the peer-reviewed academic papers of several hundred scientists.

This report spoke of "new and stronger evidence" that human activities were warming the globe, a stronger stance than in its previous report in 1995.

"It's quite clear that what Exxon are publishing is not the IPCC (position)," Ward told Reuters.

His letter to Exxon, referring to two company publications this year, said: "I am writing to express my disappointment at the inaccurate and misleading view of the science of climate change that these documents present."

Responding to the Royal Society's letter, Exxon said in a statement that it did accept the contribution of greenhouse gases such as carbon dioxide (CO2) to climate change.

"Contrary to the Royal Society's assertion, Exxon Mobil recognises ... CO2 emissions are one of the contributing factors to climate change," it said.

"We refute any suggestion that our reports are inaccurate or misleading," it said, adding it had founded a climate and energy research programme at California's Stanford University.

LOBBY GROUP FUNDING

Ward said that at a July meeting with Exxon the oil company had pledged to him that it would stop funding lobby groups that misrepresented the consensus view on climate change science.

An Exxon spokesman denied it had agreed to stop any such funding, saying the company annually reviews its funding of organisations and is now in the midst of one such review.

The review includes all charitable organisations it supports and is not in response to Royal Society pressure, but rather just part of its normal budgeting process, Exxon said.

According to Ward's own analysis of Exxon's Corporate Giving Report, the company last year funded 64 groups conducting climate change research, of which 25 were in line with mainstream climate science and 39 were "misleading."

The latter category included the Centre for the Study of Carbon Dioxide and Global Change, to which Exxon gave US$25,000 in 2005, the Exxon website shows.

The Centre's Web site says: "There is no compelling reason to believe that the rise in temperature was caused by the rise in CO2."

An Exxon Mobil spokesman said such funding did not mean that the company agreed with the views of all of these groups.

"We do take this issue very seriously," he said. "These organisations do not speak on our behalf, nor do we control their views and messages. They may or may not hold similar views to ours."