The media column - Peter Wilby gives a science lesson

My advice to journalists is the same as that given to Woodward and Bernstein at the start of the Wat

Every now and then you will read a large and alarming newspaper headline about global warming. On 19 August, for example, the Independent devoted its front page to how two leading contenders for US presidential nominations in 2008 - Hillary Clinton for the Democrats, John McCain for the Republicans - had visited Alaska. Evidence of climate change, they found, was "too stark to ignore": the effects of soaring temperatures, melting permafrost and retreating sea ice were causing people "to freak out". That day, no other paper reported this story. Instead, the Guardian (which did cover Alaska on 22 August) reported that two Russian physicists had wagered $10,000 that the world will cool between 2012 and 2017.

Eight days earlier, the Guardian had led its front page with an even more alarming story. A "vast expanse" of frozen peatbog in Siberia was thawing. This could be a "tipping point" that quickened global warming by releasing billions of tonnes of methane. The story, based on a paper in that week's New Scientist, was in the public domain; but the only other daily paper to report it, perhaps surprisingly, was the Daily Telegraph, in a single column on page 10.

This is typical of the erratic manner in which global warming is covered. A terrorist threat will be reported prominently in all papers, even when it comes from unnamed "security sources". The threat of global warming is less tangible and immediate. Although nobody would argue that a terrorist attack might be good fun, some stories about climate change make it sound quite benign. Two days after its Siberian alert, the Guardian, in common with several other papers, headlined how rising temperatures could lead to the British taking siestas. Two days after that, the Times celebrated the growing production of exotic fruits in Britain, with almonds growing in Devon, tea in Cornwall and kiwi fruit in Kent. And, as the Guardian's story on 19 August showed, there is still a small band of climate-change sceptics. Unlike the two Russians, most of them have stopped saying that global warming isn't happening and have fallen back to the position that human beings aren't to blame.

If challenged on that, the sceptics argue we'll all cope anyway.

I do not envy editors and specialist correspondents who have to decide which scientific scares to take seriously. Some critics argue that those who deny global warming are as isolated and as undeserving of a hearing as the creationists who deny Darwin. Yet the collective wisdom of scientists has sometimes proved wrong, as anybody who follows advice about what we should or shouldn't eat will know.

My recommendation to journalists is the same as that given to Bob Woodward and Carl Bernstein at the start of the Watergate investigation: follow the money. A scientific consensus should be treated with scepticism if the consensus happens to suit the interests of the rich and powerful. Even though scientists are not exactly corrupt, their work depends heavily on research contracts, grants and sponsorship. When nearly all of them are willing to resist the paymasters, I reason, they must be pretty damn convinced.

So the consensus that BSE ("mad cow disease") could not be transmitted to humans was always suspect because the agricultural industry had the money. I remain sceptical of the consensus that we shall all be done in by bird flu (yes, you can laugh if I catch it this winter), because the money is with the pharmaceutical industry, which can make millions selling drugs and vaccines we won't need. Conversely, I believe sugar and salt must be bad for us, as most scientists say, because the entire food industry is desperate to believe they are not.

On this basis, global warming is a no-brainer. Few manufacturers of wind turbines have a financial interest in causing alarm. Nearly all the money is with the oil industry and, if you dig deep enough, you find that many climate-change sceptics get help, directly or indirectly, from that source. The counter-claim that hundreds of climate scientists are motivated by politics - which presumably means they want to overthrow capitalism or undermine America - just doesn't stack up. So when scientists say we're all going to drown or fry if we carry on using fossil fuels, they should be taken seriously, and put on the front pages. QED.

Most annoying story of last weekend: the revelation in the Financial Times that my rival media commentator John Lloyd got grade A and 60 marks out of 60 for an A-level paper. The FT got four of its staff to sit papers in their specialist subjects. While James Blitz, the political editor, scraped only a grade C in government, Lloyd got full marks in media studies. Regular NS readers will recall that Lloyd (who also now edits the FT Magazine) left this paper in a much-publicised strop when I was editor. The FT reported that, while Lucy Kellaway (management columnist) wrote six pages for her business studies paper, Lloyd "densely covered" more than 13 pages. I can picture them. Concision was never one of his virtues.