The climate has changed. There can now be no doubt. Change is happening and it is definitely man-made: the changed financial climate is a plausible pretext for any nation that wishes to renege on its environmental promises.

Last March EU leaders agreed to a target of reducing CO2 emissions by 20 per cent by 2020 on 1990 levels. Now, in advance of Wednesday's EU energy summit, the Polish Prime Minister, Donald Tusk, is leading a retreat. He is likely to resist a reform to the trading-emissions scheme by which EU governments would be forced to buy the right to emit carbon dioxide. Mr Tusk, echoed by Frank-Walter Steinmeier, the German Foreign Minister, was quite explicit that the international financial crisis was the culprit.

Back-pedalling on carbon emissions because of the crisis is not surprising, but it is wrong. Businesses and individuals clearly will be looking for ways to cut costs. But cuts that postpone progress towards lower carbon output will prove ruinously expensive in the long run. For European governments to abandon responsible - and in some cases exemplary - positions on climate change because of tough economic times is not just disingenuous, but foolish.

It is also both complacent and overoptimistic to argue that falling economic capacity will reduce consumption, thereby making people more provident in their expenditure of resources.

The looming recession cannot be relied on to save the environment inadvertently. The greatest inroads into climate change will, in the end, derive from the endless ingenuity of human minds. That requires speculative investment that can only be harmed by the diminution of surplus funds. It requires governments, therefore, to be bolder. The pace of change in car engines, for example, is not held back by lack of scientific creativity. It is held back by politicians not prepared to confront their electorates.

Governments need to be brave in the face of difficult economics. The Stern report concluded that the costs of inaction will dwarf the costs of action and that there will be a green employment dividend. Perhaps there will - but this argument is unlikely to impress the Polish Prime Minister.

Poland and Germany must acknowledge, nonetheless, that energy efficiency is good for climate change and that reduced bills should be easy to sell in straitened times. The £910 million announced recently by the British Government for energy efficiency initiatives is a small but salutary move, and it is to be hoped that the argument gains traction in the United States. Energy efficiency, in turn, increases energy security. In the UK, the Government has been wise to press ahead with renewing our nuclear supply, and the desire to reduce energy dependence on Russia has an obvious attraction in the United States.

The collision of financial crisis and climate change presents an opportunity for political leadership. Already David Cameron risks looking like a fair-weather friend to the environment. Having used climate change to present a new kind of Conservative to the nation, he now needs urgently to arrest the slow retreat that he seems to have conducted this year. It is to be hoped that Gordon Brown resists the specious link between credit crunch and carbon cowardice that others may try to force upon him.