The belief that human beings are masters of the planet dies hard. I cannot count the number of times I have heard environmentalists warning that we have only ten, 20 or 30 years in which we can prevent disaster. The implication is that, provided we apply sufficient intelligence and political will, we can arrest the dangerous environmental changes that are under way - as if global warming weren't a physical process that does not wait on humans. The assumption that we can stop it becomes less scientifically tenable by the day, and is in fact not much more than a green version of anthropocentrism.
In Heat, the environmental activist and thinker George Monbiot tries to bring the debate about climate change closer to known facts and reasonable conjecture, avoiding the woolly thinking that is so prevalent on the subject. The result is a book that anyone who thinks they know what should be done about global warming must read. One virtue of Monbiot's consistently heretical inquiry is that he recognises the magnitude of the danger: if present trends continue, the result could be a climate shift analogous to that which wiped out much of the world's biodiversity when the Permian era came to an abrupt end roughly 250 million years ago. Even if the change turns out to be much less dramatic, we can forget about carrying on with business as usual.
Monbiot clears the mind of a great deal of cant. As he shows, many fashionable environmental nostrums are either pointless or harmful in their effects. Micro wind-turbines are not worth the time and money spent on them: Britain needs a larger national grid, not a smaller one. Biofuels are a particularly dangerous panacea. To reduce our dependence on fossil fuels significantly, we would need to plant them on a vast scale, further reducing the world's shrinking inheritance of land and water. A large part of the present crisis is a result of the agricultural destruction of wilderness, which plays a vital role in maintaining global climate. Between 1985 and 200o, production of palm oil - currently the cheapest source of biofuel - accounted for nearly 90 per cent of deforestation in Malaysia. A large-scale shift to biofuels - as advocated by George W Bush, for example - could have a comparable effect worldwide, increasing the harm done by farming while diminishing food production. The result would damage human welfare and the biosphere as a whole. As Monbiot notes: "Biofuel production is a formula not only for humanitarian disaster but also for environmental catastrophe."
This is not the only example of environment-alist policies that can prove to be self-defeating. It is a pity Monbiot says nothing about the phenomenon of global dimming. As well as greenhouse gases, humans are releasing aerosol particles into the atmosphere through industry and air travel. These are pollutants, but one of their effects is to reflect sunlight back into space - dimming the sky and at the same time cooling the planet. Reducing this kind of pollution - by discouraging flying, for instance, as Monbiot proposes - would make the world cleaner; it would also accelerate global warming.
If so many of the policies touted by environmentalists are counter-productive, how are we to stop the planet burning? Monbiot allows some scope for technical fixes - he is optimistic that new, low-cost methods of electricity transmission can be developed, for example - but the implication of his analysis is that reducing global emissions depends largely on changing the way we live. Since he accepts that emissions need to be cut by around 90 per cent over the next 30 years, the task is plainly a formidable one, and he struggles valiantly to show how this could be done. Some system of carbon rationing must be devised, he believes, and the economy be transformed by redesigning the public transport system, replacing out-of-town shopping centres by a system of warehouses and deliveries, and constructing more energy-efficient homes.
It is hard to judge whether this programme would have the desired effect, but in a sense the question is immaterial. Monbiot is more realistic than most greens. Yet, like them, he overlooks some crucial facts. Britain's emissions of greenhouse gases make up a tiny percentage of emissions worldwide, and while reducing them by 90 per cent might generate a pleasing sensation of virtue, it would have a negligible impact on climate change. Monbiot's programme would have to be implemented globally to be feasible at all, and applied most vigorously in the countries that are the largest sources of emissions: China, India and the United States. However, the first two countries cannot afford to reduce their emissions by anything like the necessary amounts, and a majority of the population in the third country will not accept the changes in lifestyle that a 90 per cent reduction demands.
What of the rest of the world? Does Monbiot seriously believe that oil-rich Russia and resurgent Iran are going to accept policies that penalise fossil-fuel production merely to avert a catastrophic alteration in the world's climate? Or that western countries are likely to hold off from developing Canadian tar sands - which could potentially supply more energy than Saudi Arabia, but at the cost of producing far more greenhouse gases - just because going ahead could set the planet on fire?
However sensible it may be in parts, there is a profound unreality surrounding the programme of action Monbiot proposes. "Curtailing climate change must be the project we put before all others," he writes. But who are "we", exactly? Humanity at large is ridden with intractable conflicts, and delusional bigots rule its most powerful state. An American air attack on Iran would produce an oil shock greater than any that has yet occurred, triggering the search for other sources of energy - many of them dirtier than oil. Moreover, continuing growth in human numbers (a crucial factor in the worsening en vironmental situation that Monbiot mentions only once in the book, giving it less than a single complete sentence) is increasing resource scarcity around the world. It is always claimed that the human environmental impact is a matter of per capita resource rather than sheer numbers, but there is an upper limit. By conservative estimates, there will be some two billion more human beings on the planet 50 years from now. Coming decades are far more likely to bring intensifying resource wars than concerted action against climate change.
There is, in fact, not the remotest prospect of the world adopting anything like Monbiot's programme, but once again this may not matter. As he recognises, it may already be too late: "Because the carbon released now stays in the atmosphere for some 200 years and causes climate change many years into the future, there is perhaps a 30 per cent chance that we have already blown it." It is a sobering admission, from which Monbiot immediately retreats. "I am writing this book in a spirit of optimism," he declares, "so I refuse to believe it."
Here and throughout the book, Monbiot is torn between the angry passion of the activist and the stoic lucidity of the analyst. Like nearly all environmentalists, he believes we would lose nothing by moving towards a more sustainable way of life. But is this actually the case? If there is a 30 per cent chance that the ground on which we are standing is going to give way whatever we do, what is the point in focusing all our energies on trying to make our position more sustainable? Growing numbers of scientists believe the probability of highly disruptive climate change occurring during the present century may be a good deal higher than 30 per cent. If this is so, will we not be better employed preparing to cope with the disruption than by pretending that it can still be stopped?
There are some useful things that can be done. In Britain, we can increase flood defences against rising sea levels, secure our electricity supplies by commissioning replacements for existing nuclear power stations, develop new technologies for cleaner coal and create wildlife corridors to help other species adapt. But first we have to accept that we cannot control the process of climate change we have set in motion. Unfortunately this requires an insight into the limits of human power that is beyond most environmentalists. Like the rest of humankind, they cannot bear very much reality.
John Gray is the author of "Straw Dogs: thoughts on humans and other animals" (Granta Books)