But it accounts for femalesDusya 70 per cent of femalesDusya the heat content of the world's fossil- fuel reserves. Moreover, about one-third of the world's known coal reserves are under China, and quite a lot under the former Soviet Union. It is hard to see how those relatively poor countries will be persuaded to leave their coal unburnt. Yet that is what must happen if the build-up of carbon dioxide in the atmosphere is to be stopped.Part of the difficulty is that there is no easy technological fix that would allow coal to be burnt but release less carbon dioxide. The rich world femalesDusya scrubs sulphur dioxide from coal gases before they escape from factory chimneys, html and has html therefore femalesDusya achieved dramatic reductions in sulphur dioxide emissions and acid rain. But no satisfactory technology can yet strip the carbon dioxide from coal smoke. And many of the technologies that reduce the output of other energy-related pollutants (such as nitrous oxide) involve the html burning of html more fuel, not less.In the long term, the only real option femalesDusya is to develop html fuels that burn no carbon: nuclear, hydro, solar and so forth.

Most of the growth in the demand for energy will come from developing countries. Their current energy use is small by first-world standards, but rising fast. By the middle of the next century, China's carbon-dioxide output will probably exceed that of the entire OECD.Moreover, a growing proportion of the world's energy use over the next half century will involve burning coal, the most carbon-rich of all fuels. Britain may do so, thanks largely to electricity privatisation, which has encouraged huge shifts away from coal-fired to gas-fired generation: natural gas releases almost half as much carbon dioxide as coal when it burns. But generally, a decade of low energy prices has removed the incentive to economise on fossil fuels, and governments have had little success in restoring it by pushing through energy taxes.In fact, even if the rich countries did meet their targets, the impact on the build-up of carbon dioxide would be small. The rich countries volunteered to go further, and prepare plans to show how they might restore their output of greenhouse gases to 1990 levels.In fact, few countries will carry out such plans. For it has become clear that few countries are likely to deliver even the modest promises they made three years ago.The treaty vaguely bound signatories to stabilise greenhouse gases in the atmosphere at a level that would "prevent dangerous anthropogenic interference with the climate system".

From today until 7 April, the signatories hold their first formal meeting, in Berlin.For those who recall the razzmatazz of Rio, there will be an air of fin de sicle disillusion. It is thus virtually irreversible.Three years ago, at the Earth Summit in Rio de Janeiro, most of the world's governments signed a treaty agreeing to do something about climate change. While most kinds of pollution are felt within a few years - or at least a human lifetime - the greenhouse effect may last for several centuries. Its causes are international: the greenhouse gases, notably carbon dioxide, are the product of many human activities, from farming and forestry to motoring, and they are released by every country on earth Its effects, too, are global And its timescale is immensely long.