The US will have to help combat climate change if extreme weather events are to be avoided, the UK government's chief scientist has warned.
Sir David said the UK needed to know to deal with climate change
Sir David King told a Lords select committee inquiry into climate change of concerns about possible environment changes if global temperatures rise.
Last summer's European heat wave and flooding two years earlier could occur more frequently over time, he said.
Action to "reduce the risks" needed to be taken by nations, including the US.
Possible changes could include ocean currents, monsoons and melting polar ice caps if global temperatures are allowed to rise unchecked through carbon fuel burning.
"These severe events will occur more frequently, and the understanding of what is driving this will become more apparent," Sir David said.
"I think nations around the world will understand that in order to reduce the risks action will have to be taken.
"And amongst those nations has to be the United States, which is currently responsible for emitting about a quarter of the world's carbon dioxide."
The US has been criticised worldwide since President Bush pledged not to support the Kyoto Protocol, which sets legally binding global warming reductions.
Sir David's appearance at the select committee came a day after he denied reports that he was being "muzzled" by Downing Street.
No 10 had sent a memo to him after he said climate change was a bigger problem than the threat of terrorism.
However, Sir David has continued to conduct media interviews.
In January, Sir David wrote an article for the American journal Science criticising the US government for failing to take global warming more seriously.
"In my view, climate change is the most severe problem we are facing today, more serious even than the threat of terrorism," he wrote.
Predictions coming true
He told the Lords committee that the scientific community had reached a consensus that global warming was manmade and "is essentially fossil fuel burning".
Sir David also called on petrol companies BP, Amoco and Shell to put money into a new UK energy research centre.
He said this would have a key role in predicting climate change and temperature rise.
A key energy research laboratory, part of the old Central Electricity Generating Board, was shut down when the electricity industry was privatised in the 1980s.
Details about the new research unit would be unveiled shortly, he said.