THISWEEK deputy prime minister John Prescott and environment minister Michael Meacher are in Kyoto negotiating binding international targets for reductions in greenhouse gas emission to combat global warming. Progress at these discussions is vital not only for Britain, but for the world.

On current trends carbon dioxide concentrations in the atmosphere will be about twice pre-industrial values by about 2050. The Intergovernmental Panel on Climate Change warns that the Earth's climate will warm as a result. Floods and droughts could become more common and severe. Sea levels are expected to rise by around 50 centimetres over the next century.

By 2020 climate change in Britain is predicted to equate with a northward shift of some 100 to 200 kilometres. Many of the affected plants, animals and indeed ecosystems will not be able to respond fast enough to move with the temperature change.

In the longer term, climate change could interfere with mechanisms driving the Gulf Stream, which greatly warms the climate of northern Europe. The heat transported towards Britain by the Gulf Stream amounts to ,000 times the nation's total power generation capacity. If this is lost, Britain is threatened, as Mr Meacher said recently, with a climate "more like Siberia than the south of France".

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Because of the long residence time of carbon dioxide in the atmosphere (about 100 years), there are long lags between action to cut levels and the levels actually stabilising. The world must act quickly. Tony Blair's appearance at the United Nations General Assembly special session in June, reaffirming the UK's domestic aim of a 20 per cent reduction in carbon dioxide, shows that this government takes the issue seriously.

Unfortunately, not all countries agree the need for early action. The economic debate tends to be split into two groups. One concludes that strong and early action is essential lest we (in President Clinton's words) "burden our children with our failure to act". The other fears that such action will be expensive, cost jobs and reduce economic competitiveness.

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The nay-sayers' arguments deserve attention. But experience with CFCs and lead in petrol suggests that abatement costs are lower than initially feared. Several recent studies suggest that significant reductions in greenhouse gas emissions are technically possible and economically feasible by increasing use of energy-efficient technologies. Many will bring other benefits, including increased industrial efficiency and environmental gains such as improved air quality.

The UK has already moved to reduce carbon dioxide emissions, mainly through shifting from coal to gas power generation. Emissions in 2000 will be 4 to 8 per cent below 1990 levels. The next steps will be a lot harder.

The task falls on all sectors of society:industry, road and other transport, and in the home and workplace. In the short term, existing technologies or those under development can reduce emissions. Fuel bill savings will partially or completely offset costs. Policy measures to accelerate technology development and encourage its diffusion and transfer will help. An integrated transport policy should reduce vehicle emissions, but will not of itself be sufficient without cleaner fuels, more efficient engines and alternative energy sources.

Industry should see climate change as an opportunity, not as a threat. But big changes will be needed in the energy, transport and construction industries, in terms of cost-effective investment, to achieve much greater efficiency in production and use and the development of appropriate technologies.

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We also need to think long. Any target agreed at Kyoto must only be a first step. Following Kyoto, the government will hold a national consultation on measures largely to meet its international target and will launch a debate about how to move to its aim of a 20 per cent reduction in carbon dioxide emissions on 1990 levels by 2010.

The main options might include measures to promote more efficient production and energy use, drives to develop combined heat and power schemes and to generate more electricity from renewable sources, and creating a more sustainable transport system.

The UK's contribution to climate change research is strong out of all proportion to size or research spending. We should maintain this strength so that international policy is underpinned by fundamental understanding.

The actions needed to address climate change will be impossible to accomplish unless we are all persuaded of their need. This is hard, as the consequences lie decades in the future, yet the magnitude of tomorrow's problems depends crucially on today's actions.

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Ultimately the problem demands international cooperation and coordination. Developed countries need to take the lead. Britain should help developing nations reconcile sustainable development with emission limitation. This does not mean patronising moral exhortations nor throwing money at problems, but rather partnerships in which we explore appropriate forms of help.

Sir Robert May is chief scientific adviser to the Cabinet and head of the Office of Science and Technology.

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Perspective, page 23