There are many opinions a coporation must keep to itself, that is if it's insterested in keeping a squeaky clean, or a squeaky "green" image. Sometimes, though, a corporation feels compelled to inject something unsavory into the public debate in order to protect the bottom-line - and the best way to do this is through the age-old art of ventriloquism.

When it comes to the issue of climate change, no corporation has done better with this tricky little PR technique than ExxonMobil, which was castigated this week by the UK's prestigious Royal Society for funding organizations that work to spread doubt about the scientific consensus on climate change.

Of course, this type of ventriloquism is not without precedent.

The classic example is The Advancement of Sound Science Coalition (TASSC), a front group that the PR firm APCO-Worldwide founded in 1993 on behalf of tobacco giant Philip Morris, specifically to question the health risks of Environmental Tobacco Smoke (ETS). TASSC then engaged experts to write papers in the industry’s defence.

So who are Exxon's ventriloquist dolls when it comes to the issue of climate change? In 2005 alone, ExxonMobil spent mjore than $2.4 million on organizations that say what Exxon hasn't got the credibility or the nerve to say itself.

Here's a list, as reported on ExxonMobile's 2005 Worldwide Giving Report:

Acton Institute - $50,000
American Conservative Union Foundation - $50,000
American Council for Capital Formation Center for Policy Research - $360,000
American Enterprise Institute - $240,000
American Legislative Exchange Council - $241,500
Atlas Economic Research Foundation - $100,000
Center for Defense of Free Enterprise - $60,000
Center for a New Europe - $50,000
Competitive Enterprise Institute - $270,000
Committee for a Constructive Tomorrow - $90,000
Free Enterprise Education Institute - $70,000
Frontiers of Freedom - $140,000
George C. Marshall Institute - $115,000
Heartland Institute - $119,000
International Policy Network - $130,000
Institute for Energy Research - $65,000
Media Research Centre - $50,000
National Black Chamber of Commerce - $60,000
National Centre for Policy Analysis - $75,000
National Centre for Public Policy Research - $55,00
Pacific Research Institute for Public Policy - $95,000

That's just for 2005. According to past reports, Exxon has contributed at least $12 million since 1998 to groups that deny that climate change is happening, deny that humans are responsible, deny that the ratio of CO2 is climbing dangerously in the atmosphere, deny that Kyoto is a good (if inadequate) first step - deny, deny, deny.

There's nothing wrong with making a contrarian argument, and nothing wrong with a PR firm helping a corporation put its best foot forward in public. But these "think tanks" should be forced to carry a tobacco-package disclaimer on everything they write: "These opinions were brought to you with a foundational grant from the most successful fossil fuel purveyor in the world."

The Royal Society is right: what's happening is a travesty - a grand public lie - and it should stop.