Are we witnessing the beginning of a real-life satire, at once amusing and terrifying? Its theme is the smothering of the nuclear power risk by catastrophic climate change and the oil crisis. At the G8 meeting in Hokkaido last week the US president, George Bush, reiterated his plea for the construction of new nuclear energy plants. At the start of this week, Gordon Brown, announced the fast-tracking of eight new reactors and called for "a renaissance of nuclear power" in a "post-oil economy". It is as if a world that wishes to save the climate must learn to appreciate the beauty of nuclear energy - or "green energy", as Germany's Christian Democratic Union general secretary Ronald Pofalla has rechristened it. Given this new turn in the politics of language, we should remind ourselves of the following.

A couple of years ago the US Congress established an expert commission to develop a language or symbolism capable of warning against the threats posed by American nuclear waste dumps 10,000 years from now. The problem to be solved was: how must concepts and symbols be designed in order to convey a message to future generations, millennia from now? The commission included physicists, anthropologists, linguists, neuroscientists, psychologists, molecular biologists, classical scholars, artists, and so on.

The experts looked for models among the oldest symbols of humanity. They studied the construction of Stonehenge and the pyramids and examined the historical reception of Homer and the Bible. But these reached back at most a couple of thousand years, not 10,000. The anthropologists recommended the symbol of the skull and crossbones. However, a historian reminded the commission that the skull and crossbones symbolised resurrection for the alchemists, and a psychologist conducted an experiment with three-year-olds: if the symbol was affixed to a bottle they anxiously shouted "poison!", but if it was placed on a wall they enthusiastically yelled "pirates!".

Even our language fails, then, when faced with the challenge of alerting future generations to the dangers we have introduced into the world through the use of nuclear power. Seen in this light, the actors who are supposed to be the guarantors of security and rationality - the state, science and industry - are engaged in a highly ambivalent game. They are no longer trustees but suspects, no longer managers of risks but also sources of risks. For they are urging the population to climb into an aircraft for which a landing strip has not yet been built.

The "existential concern" being awakened across the world by global risks has led to a contest to suppress large-scale risks in political discussion. The incalculable dangers to which climate change is giving rise are supposed to be "combated" with the incalculable dangers associated with nuclear power plants. Many decisions over large-scale risks are not a matter of choosing between safe and risky alternatives, but between different risky alternatives, and often between alternatives whose risks are too qualitatively different to easily compare. Existing forms of scientific and public discourse are no match for such considerations. Here governments adopt the strategy of deliberate simplification. They present each specific decision as one between safe and risky alternatives, while playing down the uncertainties of nuclear energy and focusing attention on the oil crisis and climate change.

The striking fact is that the lines of conflict within world-risk society are cultural ones. The more global risks escape the usual methods of scientific calculation and turn out to be a domain of relative non-knowledge, the more important becomes the cultural perception of specific global risks - that is, the belief in their reality or unreality. In the case of nuclear power, we are witnessing a clash of risk cultures. Thus the Chernobyl experience is perceived differently in Germany and France, Britain, Spain or Ukraine and Russia. For many Europeans the threats posed by climate change now loom much more largely than nuclear power or terrorism.

Now that climate change is regarded as man-made, and its catastrophic impacts viewed as inevitable, the cards are being reshuffled in society and politics. But it is completely mistaken to represent climate change as an unavoidable path to human destruction. For climate change opens up unexpected opportunities to rewrite the priorities and rules of politics. Although the rise in the price of oil benefits the climate, it comes with the threat of mass decline. The explosion in energy costs is gnawing away at the standard of living and is giving rise to a risk of poverty at the heart of society. As a consequence, the priority which was still accorded energy security 20 years after Chernobyl is being undermined by the question of how long consumers can maintain their standards of living in the face of the steady increase in energy prices.

Yet to disregard the "vestigial risk" of nuclear energy is to misunderstand the cultural and political dynamic of the "residual-risk-society". The most tenacious, convincing and effective critics of nuclear energy are not the greens - the most influential opponent of the nuclear industry is the nuclear industry itself.

Even if politicians were successful in the semantic reinvention of nuclear power as green electricity, and even if the opposing social movements were to dissipate their energy through fragmentation, this is all nullified by the real opposing force of the threat. It is constant, permanent and remains present even when exhausted demonstrators have long since given up. The probability of improbable accidents increases with the number of "green" nuclear plants; each "occurrence" awakens memories of all the others, across the world.

For risk is not synonymous with catastrophe. Risk means the anticipation of catastrophe, not just in a specific place but everywhere. It doesn't even have to come to a mini-Chernobyl in Europe. The global public need only get wind of negligence and "human error" somewhere in the world and suddenly the governments advocating "green" nuclear energy will find themselves accused of gambling recklessly and against their better judgment with the security interests of the population.

What will become of "responsible citizens" who cannot sense these threats produced by civilisation, and hence are robbed of their sovereign judgment? Consider the following thought experiment. What would happen if radioactivity caused itchiness? Realists, also known as cynics, will answer: people would invent something, for example an ointment, to "suppress" the itching. A profitable business with a good future. Of course, persuasive explanations would immediately be offered explaining that the itching was unimportant, that it could be traced back to other factors. Presumably such attempts to explain things away would have a poor chance of survival if everyone ran around with skin rashes scratching themselves and fashion shoots and business meetings were accompanied by incessant scratching. Then the social and political ways of dealing with modern large-scale hazards would face a completely different situation because the issue under dispute and negotiation would be culturally visible.

· Ulrich Beck is author of World Risk Society and professor of sociology at Munich's Ludwig-Maximilians University and the London School of Economics

u.beck@lmu.de