Another warning for President Bush that he needs to act fast to prevent climate change

Amid all the studies and first-hand observations relating to climate change, it is the small details that often convey the bigger message most effectively. One such is the forecast, contained in a comprehensive study released this week about climate change in the Arctic, that polar bears could become extinct. The study, the work of more than 300 scientists, says that the thinning of Arctic ice is depriving polar bears of life-sustaining conditions for hunting. The risk is that they could become so thin that they lose the ability to reproduce.

Amid all the studies and first-hand observations relating to climate change, it is the small details that often convey the bigger message most effectively. One such is the forecast, contained in a comprehensive study released this week about climate change in the Arctic, that polar bears could become extinct. The study, the work of more than 300 scientists, says that the thinning of Arctic ice is depriving polar bears of life-sustaining conditions for hunting. The risk is that they could become so thin that they lose the ability to reproduce.

While the decline of the polar bear population, like any diminution of the diversity of animal life, would be highly regrettable, it is but one symptom of the adverse effects of climate change on our planet overall. Among the findings of the same study are a significant rise in average temperatures in Alaska, northern Canada and eastern Russia; the much earlier break-up of sea ice in Hudson Bay and the eventual melting of the polar ice cap altogether. This is some of the most compelling evidence ever presented for the accelerating effects of global warming. It needs to be treated seriously.

In many parts of the world, the message is already being heeded. Both chambers of the Russian parliament have voted to ratify the Kyoto treaty on climate change, and President Putin has signed it into force. The accession of Russia will bring the treaty into effect worldwide early next year. Mr Putin's decision, while clearly political, is especially laudable, given that Russia arguably has as much to gain - a warmer, more hospitable Siberia - as to lose from a rise in global temperatures.

The signal exception - the one large country that is not only doing nothing to slow the effects of climate change, but is still refusing to accept the basic arguments - is the one country whose contribution could count for more than that of any other: the United States. How often is it necessary to rehearse the facts? Among developed countries, the US is the world's biggest consumer of fossil fuels; it is the world's biggest polluter, a nation of multiple car-owners with some of the most lightly taxed fuel and some of the least demanding regulations on energy efficiency. It is the only G8 country not to have signed up to Kyoto.

Although a number of US states, notably in the north-west of the country and adjoining Canada, are environmentally aware and alert to the risks of climate change, the federal government and Congress have rejected the Kyoto treaty outright, arguing that it would increase spending and cost jobs. The re-election of George Bush and the increased Republican majorities in Congress offer no hope at all that there will be any change of heart.

On the contrary, a senior Bush adviser and global warming specialist, Myron Ebell, has already been involved in a spat with the British government's chief scientist, Sir David King, challenging his credentials to speak about climate science. Sir David's offence was apparently to have described climate change as a greater threat to the world than terrorism. It can surely be only a matter of time before Mr Bush re-submits his Bill to authorise prospecting for oil and gas in the ecologically protected region of Alaska. Worse, the new Congress might even be disposed to pass it, especially if prices of imported energy continue to rise.

Climate change and US opposition to Kyoto are issues that the Prime Minister must raise when he meets Mr Bush in Washington today and tomorrow. As Mr Blair stated, before his departure, perhaps with too great a sense of defeatism, "None of Britain's aims on climate change, Middle East peace or other world affairs can be met without US help."

The point of a close alliance, however, is not only to discuss issues where there is, or could be, agreement, but to present the argument when the differences are principled and acute - as they are on Kyoto. If scientific formulae, melting polar ice-caps and rising water levels are insufficient to drive the message on climate change home to Americans, perhaps the prospect of starving polar bears will.