The furious argument is about whether or not the world's environment is deteriorating or improving. At heart is the very nature of belief and the way we perceive the world around us. An Observer article kicked off the worldwide debate last summer when it released details of a book by Bjorn Lomborg, a former Greenpeace member and professor of statistics at Aarhus University in Denmark, in which he insisted that the doom and gloom predictions of most environmental campaigners are misleading and exaggerated. With a barrage of statistics, he claimed that the amount of forest on Earth was increasing, there was no mass extinction of species, the oceans and air were getting less polluted and the world's resources weren't running out.

His attack on the core beliefs of many in the environment movement was met with hostile denunciations, accusing him of being a liar and a fraud, and earning the nickname of 'Antichrist'. Websites were set up to denounce him, and when he came to sign books in Oxford an environmental campaigner threw a baked Alaska in his face.

The science magazine Nature - which said that Lomborg 'employs the strategy of those who argue that... Jews weren't singled out by the Nazis' - was only outshone in its hostility by Scientific American, which dedicated 11 pages of comment and review to thoroughly trashing Lomborg's work. The editor-in-chief of the magazine, John Rennie, introduced the denunciation with a comment in which he declared Lomborg's book 'a failure'.

Lomborg, who has been backed by many leading scientists and the Economist magazine, demanded a right to reply and was offered only one page to be published many months later. When Lomborg then sought to defend his book on the internet with a blow-by-blow rebuttal, the magazine forced him to take it down by threatening to sue him for copyright infringement.

Last week Patrick Moore, the founder of Greenpeace International - who has since turned against the extremists in the environmental movement - has launched a vigorous campaign to defend Lomborg and his views, putting up Lomborg's defence on his own website and persuading other sympathisers to do the same.

Moore said: 'This is a blatant attempt by Scientific American to stifle free debate. It is completely ridiculous for Scientific American to claim that publishing the text of their editorial as part of a response interferes with selling the article.

'The January edition has been off the news-stands for over a month. It is obvious that their motivation is political, to stifle debate and to defend their support for environmental extremists who preach that the world is coming to an end, even though the facts do not support such a pessimistic view.'