KATRINA MADE the Bush Administration take climate change seriously. Fortunately we have had no Katrina-like episode in this country, but the warnings are plain to see.

In recent months scientists across the world have reported compelling evidence that we face dramatic melting of Arctic sea ice, a shutdown of global ocean circulation systems in the North Atlantic, huge methane releases from melting permafrost in Siberia and Alaska, more violent hurricanes worldwide, and “mega-droughts” from northern China to the American West. Already the World Health Organisation estimates that 160,000 people die each year from the impacts of climate change, notably malaria, dysentery and malnutrition.

Some may dismiss this as remote from Britain, unlikely to affect us and anyway a risk only in the distant future. They are wrong. George Bush’s leading climate modeller, Jim Hansen, said a month ago that we have “at most ten years” to make the drastic cuts in emissions that might head off climatic catastrophe.

Nor, in one highly interconnected world, are these convulsions irrelevant to us. Rising sea levels, desertification and shrinking freshwater supplies will create up to 50 million environmental refugees by the end of this decade, according to the UN. If the ocean “pumps” around Greenland falter, northern European temperatures would plummet to those of Siberia. The London School of Hygiene and Tropical Medicine estimates that of ten of the world ’s most dangerous vector-borne diseases, nine will increase their coverage because of climate change. As the Greenland and Antarctic ice sheets melt, rising sea levels will threaten coastal cities worldwide (including London), as well as nuclear power stations and chemical waste dumps sited in coastal areas. Food supplies worldwide will be disrupted by intensifying droughts, and industrial agriculture will be particularly vulnerable to a surge in pathogens and pests from warmer temperatures.

Yet climate disaster is still only in its very early stages: this is not a linear but a dynamic process of intensification. Indeed, at certain “tipping points”, emissions of greenhouse gases could leap unpredictably. The impact of this on human civilisation is at this stage unknowable.

So is all this irreversible? Some is, but far the greater part is still to come and can be slowed and, over time, halted. But it requires more urgent and radical change in our transportation, economic systems and lifestyles than governments or industries anywhere have yet seriously contemplated.

What then is to be done? If climate change is driven primarily by the burning of fossil fuels, the world must diversify quickly into renewable sources of energy — wind power, biomass, wave and tidal power and solar energy. Carbon capture and storage may be an option, but no clean coal-technology prototype has yet been built.

But are renewables a feasible option? Europe’s offshore wind potential in waters up to 30m deep could theoretically supply all of the Continent’s power. China has so much wind energy that it could double its electricity generation by using it. The US Department of Energy estimates that just three states — North Dakota, South Dakota and Texas — have enough wind energy to meet America’s entire electricity requirements.

Equally, in the field of transport, while gas may provide a transitional feedstock to make hydrogen for fuel celldriven vehicles, a cost-competitive technology should be developed as rapidly as possible to make hydrogen from renewables.

All countries have to be involved in a global solution. The Kyoto Protocol aimed to get the 35 main industrialised countries to reduce their greenhouse gas emissions by 5 per cent by 2010, compared with 1990. If the world — 185 countries — is to achieve what the scientists say is necessary, a cut of 60 per cent by 2050, China, India, and the other big developing countries must sign up to significant action (even if not immediately to Kyoto targets) to reduce carbon emissions within limited timescales. Of course the US, the biggest polluter, must also be brought in at the earliest time.

Air travel — the single fastest rising cause of greenhouse-gas emissions — should now be urgently incorporated into Kyoto and given emission-reduction targets like other industries. The EU emissions trading system for the main industrial sectors should be progressively tightened.

But energy conservation is just as important for domestic households as for industry, since the waste of energy by both sectors is enormous. Higher standards should be laid down in building regulations, as in Sweden, and bigger incentives given to families to switch to renewables, both solar thermal panels and microgeneration, for water heating and house warming, as in Germany. If the energy-efficiency rating of a house had to be provided as part of a vendor’s pack at a house sale, it would provide all house owners with a powerful incentive to upgrade their insulation.

People need much bigger incenstives to use smaller engine cars and to make fewer car journeys. Above all, if a cap and trade system were applied to households as well as to industries, it would provide a market mechanism to guide individual choice while cutting domestic carbon emissions overall. Nothing less meets the challenge that confronts us all.

The author is a former Environment Minister. This is an edited version of his speech at yesterday’s Intelligence Squared/Times debate on global warming.

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