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: