Of course, it's not a crime, and it's hard to see how, in a free society, it could or should become one. But the culpability of the energy firms the climate scientist James Hansen will indict in his testimony to Congress today is clear. If we fail to stop runaway climate change, it will be largely because of campaigning by oil, coal and electricity companies, and the network of lobbyists, fake experts and thinktanks they have sponsored.

The operation sprang directly from Big Tobacco's war against science. It has used the same fake experts, the same public relations companies and the same tactics: as I showed in my book Heat, the campaign against action on climate change was partly launched by the tobacco company Philip Morris. But while the tobacco companies' professional liars were smoked out by a massive class action in the US, the sponsored climate change deniers still have massive influence over public perception. A survey published yesterday by the Observer shows that six out of ten people in Britain agreed that "many scientific experts still question if humans are contributing to climate change." This is an inaccurate perception, which results from Big Energy's lobbying.

Almost without exception, the scientists who claim to doubt that manmade climate change is taking place fall into two categories: either they are not qualified in the branch of science they are discussing or they have received money from fossil fuel companies. Of all the self-professed climate "sceptics", I have been able to find only one – Dr John Christy of the University of Alabama – who has relevant qualifications and who does not appear to have received fees from lobby groups or thinktanks sponsored by the energy companies. But even he has had to admit that the figures on which he based his claims were the results of "errors in the … data".

The others are the very opposite of sceptics. Many of them are paid to start with a conclusion – that climate change isn't happening or isn't important – then to find data and arguments to support it. In most cases, they cherrypick scientific findings; in a few cases, like the fake scientific paper attached to the celebrated Oregon petition, they make them up altogether. But people who don't understand the difference between a peer-reviewed paper and a pamphlet are taken in. The energy companies' propaganda campaign is amplified by scientific illiterates in the media, such as Melanie Phillips, Christopher Booker, Nigel Lawson, Alexander Cockburn and the television producer (who made Channel 4's documentary The Great Global Warming Swindle) Martin Durkin.

I don't believe that the energy companies should be prosecuted for commissioning the truckload of trash their sponsored experts publish. But their campaign of disinformation must be exposed again and again. Like the tobacco lobbyists, they are not only delaying essential public action; they also create the impression that science is for sale to the highest bidder.

The awful truth is that sometimes it is.