Lord May says global warming may have helped cause Hurricane Katrina's ferocity

Royal Society head Lord May said the UK risked missing its Kyoto targets after its emissions rose for two years.

"It is very difficult to criticise other countries such as the US who will not meet their Kyoto targets if we are unable to meet commitments," he said.

His statement came ahead of a climate change debate in the House of Lords.

Meanwhile, leading academics have warned that scarce and expensive energy supplies will become the norm in the UK.

What we need is courage from our political leaders Lord May UK faces energy gap

In this report, by the UK Energy Research Centre, experts said changes to the way people use and produce energy would be needed, and some nuclear power must be kept.

In his separate warning, Lord May said Department of Environment, Food and Rural Affairs (Defra) figures showed UK greenhouse gas emissions were currently 12.6% below 1990 levels, compared with a target of a 12.5% cut to be achieved in 2012.

But he warned emissions had risen for two years running.

Lord May of Oxford was also responding to Tony Blair's comments last week.

The prime minister said the "blunt truth about the politics of climate change" was that no country would want to sacrifice its economy to meet the challenge, although they all knew they must develop on a "sustainable basis".

'Bigger sacrifices'

Lord May said the "blunt truth" was that countries were not doing enough to adapt their economies and reduce emissions, and the developed world "may already be making bigger sacrifices in dealing with the consequences of climate change".

"Warmer oceans are causing more intense tropical storms and nobody can say that global warming played no part in the unusual ferocity of Hurricanes Katrina, Rita and Wilma," he said.

He said damage caused by Katrina alone was equivalent to 1.7% of US GDP.

However, he stressed the cost in the developing world would be "even greater".

He said research had shown a drop in rainfall in Ethiopia and surrounding countries, where millions already faced serious food shortages, was caused by a rise in sea temperatures in the southern Indian Ocean.

"In the developing world, climate change is about life and death, not just domestic economics," he said.

Lord May called for political "courage".

"What we need is courage from our political leaders both within and outside government, to take the actions necessary to reduce our emissions," he said.