Our dreaming will, as it has begun to do already, destroy the conditions necessary for human life on Earth. Were we governed by reason, we would be on the barricades today, dragging the drivers of Range Rovers and Nissan Patrols out of their seats, occupying and shutting down the coal-burning power stations, bursting in upon the Blairs' retreat from reality in Barbados and demanding a reversal of economic life as dramatic as the one we bore when we went to war with Hitler. Instead, we whinge about the heat and thumb through the brochures for holidays in Iceland. The future has been laid out before us, but the deep eye with which we place ourselves on Earth will not see it.

Of course, we cannot say that the remarkable temperatures in Europe this week are the result of global warming. What we can say is that they correspond to the predictions made by climate scientists. As the met office reported on Sunday, "all our models have suggested that this type of event will happen more frequently." In December it predicted that, as a result of climate change, 2003 would be the warmest year on record. Two weeks ago its research centre reported that the temperature rises on every continent matched the predicted effects of climate change caused by human activities, and showed that natural impacts, such as sunspots or volcanic activity, could not account for them. Last month the World Meteorological Organisation (WMO) announced that "the increase in temperature in the 20th century is likely to have been the largest in any century during the past 1,000 years", while "the trend since 1976 is roughly three times that for the whole period". Climate change, the WMO suggests, provides an explanation not only for record temperatures in Europe and India but also for the frequency of tornadoes in the United States and the severity of the recent floods in Sri Lanka.

There are, of course, still those who deny that any warming is taking place, or who maintain that it can be explained by natural phenomena. But few of them are climatologists, fewer still are climatologists who do not receive funding from the fossil fuel industry. Their credibility among professionals is now little higher than that of the people who claim that there is no link between smoking and cancer. Yet the prominence the media give them reflects not only the demands of the car advertisers. We want to believe them, because we wish to reconcile our reason with our dreaming.

The extreme events to which climate change appears to have contributed reflect an average rise in global temperatures of 0.6C over the past century. The consensus among climatologists is that temperatures will rise in the 21st century by between 1.4 and 5.8C: by up to 10 times, in other words, the increase we have suffered so far. Some climate scientists, recognising that global warming has been retarded by industrial soot, whose levels are now declining, suggest that the maximum should instead be placed between 7 and 10C. We are not contemplating the end of holidays in Seville. We are contemplating the end of the circumstances which permit most human beings to remain on Earth.

Climate change of this magnitude will devastate the Earth's productivity. New research in Australia suggests that the amount of water reaching the rivers will decline up to four times as fast as the percentage reduction of rainfall in dry areas. This, alongside the disappearance of the glaciers, spells the end of irrigated agriculture. Winter flooding and the evaporation of soil moisture in the summer will exert similar effects on rainfed farming. Like crops, humans will simply wilt in some of the hotter parts of the world: the 1,500 deaths in India through heat exhaustion this summer may prefigure the necessary evacuation, as temperatures rise, of many of the places currently considered habitable. There is no chance of continuity here; somehow we must persuade our dreamselves to confront the end of life as we know it.

Paradoxically, the approach of this crisis corresponds with the approach of another. The global demand for oil is likely to outstrip supply within the next 10 or 20 years. Some geologists believe it may have started already. It is tempting to knock the two impending crises together, and to conclude that the second will solve the first. But this is wishful thinking. There is enough oil under the surface of the Earth to cook the planet and, as the price rises, the incentive to extract it will increase. Business will turn to even more polluting means of obtaining energy, such as the use of tar sand and oil shale, or "underground coal gasification" (setting fire to coal seams). But because oil in the early stages of extraction is the cheapest and most efficient fuel, the costs of energy will soar, ensuring that we can no longer buy our way out of trouble with air conditioning, water pumping and fuel-intensive farming.

So instead we place our faith in technology. In an age in which science is as authoritative but, to most, as inscrutable as God once was, we look to its products much as the people of the middle ages looked to divine providence. Somehow "they" will produce and install the devices - the wind turbines or solar panels or tidal barrages - that will solve both problems while ensuring that we need make no change to the way we live.

But the widespread deployment of these technologies will not happen until rising prices ensure that it becomes a commercial imperative, and by then it is too late. Even so, we could not meet our current levels of consumption without covering almost every yard of land and shallow sea with generating devices. In other words, if we leave the market to govern our politics, we are finished. Only if we take control of our economic lives, and demand and create the means by which we may cut our energy use to 10% or 20% of current levels will we prevent the catastrophe that our rational selves can comprehend. This requires draconian regulation, rationing and prohibition: all the measures which our existing politics, informed by our dreaming, forbid.

So we slumber through the crisis. Waking up demands that we upset the seat of our consciousness, that we dethrone our deep unreason and usurp it with our rational and predictive minds. Are we capable of this, or are we destined to sleepwalk to extinction?

Evidence increasingly points to a weather system shaped more and more not by nature but by humanity. The pattern of industrial development of modern day society appears to be producing too much pollution for the world to cope with. The effects will irrevocably remake the climate for the worse.

Warning voices, carrying the threat of a future dystopia, are becoming clearer and more insistent. In today's paper John Schellnhuber, the head of Britain's foremost climate change thinktank, describes how the "parching heat experienced now could be a standard expression of an extreme overall development".

Two weeks ago Sir John Houghton, the former head of the Met Office, compared climate change to a weapon of mass destruction. "Like terrorism, this weapon knows no boundaries. It can strike anywhere, in any form - a heatwave in one place, a drought or a flood or a storm surge in another."

Respected scientists warn climate change could make the planet too hot for life itself. It may be true that the earth's atmosphere is being altered sluggishly and in an indeterminate manner - but neither of these is a reason for inaction.

Global warming is becoming part of the present. The 1990s was the hottest decade in the millennium - and 1998 was the warmest year. Bizarrely, the weight of the evidence required for policymakers around the world to act decisively is not great enough for the world's greatest polluter, America.

On gaining office, the Bush administration, with its roots in oil and big business, withdrew unilaterally from the biggest international commitment to cut greenhouse gas emissions - the Kyoto protocol. To gain some scale of how reckless this act of political vandalism was consider this: if US states were independent nations they would comprise 25 of the top 60 nations that emit greenhouse gases - Texas's emissions alone exceed France's.

Washington has deployed a mixture of indifference to the pressing nature of climate change and incredulity that anybody else was prepared to do anything about it. This was, and is, a dangerous act. Kyoto has still not come into force - Russia has yet to sign up. Even worse is that new data suggests Kyoto, designed when climate change was thought be less destructive, will be out of date by the time it becomes effective.

Changing the way we live and consume the earth's resources will impose economic costs today for environmental returns tomorrow. The future should see industry reducing carbon dioxide emissions. Energy-efficient homes and cleaner transport will help alleviate urban smog. Eventually new technologies will emerge that see green power replace fossil fuels which adversely affect the atmosphere. This tomorrow will only come into existence if governments produce policies that encourage a new form of development. Urgent changes are needed - the billions in India and China cannot live as the world's wealthy do today.