Lord Stern's report on climate change was published in 2006
Economist Lord Stern has said he is optimistic a global deal to reduce carbon dioxide emissions will be struck under Barack Obama's US presidency.
Lord Stern, who was behind the first detailed economic assessment of the impact of climate change, said US and Chinese agreement to a cut was crucial.
President George W Bush's climate views were "prehistoric" and had been seen as an obstacle, Lord Stern told the BBC.
But many now believed the new president could take a lead, he said.
"He's night and day on this issue relative to his prehistoric predecessor George Bush," Lord Stern told the BBC's Today programme's guest editor Jarvis Cocker.
"That is a very big change and, while people saw the United States as a obstacle, now people are saying well perhaps the United States could really lead on this.
"And it is going to have to - because the two big ones on this are the United States and China."
Lord Stern is now Chair of the Grantham Research Institute on Climate Change and Environment at the London School of Economics.
He said in his interview that, as well as hoping for action from the new US leadership, he was encouraged by the the much deeper global understanding of climate change and its impact.
Many countries had made a clear commitment to reducing greenhouse gases, he said, which showed things were moving in the right direction.
Technological advances would also help, he argued.
But he said he did not underestimate the scale of the task involved in creating a global agreement to combat climate change to take effect when the current Kyoto Protocol expires in 2012.
"Let's not forget just how big a challenge it is. We're trying to put together as a world the biggest international collaboration the world has seen and it requires that," he said.
"It is unavoidable that we do that if we are to be serious about this problem. So, it's a big challenge, but we have got a chance."
Lord Stern also said he believed the world could learn a number of lessons from the global economic crisis when dealing with climate change.
"The first one is that the longer you let risks fester, the bigger the impact and the bigger the crash and consequences.
"If we emit greenhouse gases the concentrations in the atmosphere build up and it gets more and more difficult to act the later you leave it.
"The second lesson is that we're really going to have to collaborate on this one."
Slowing down the work to tackle climate change during the current economic crisis would be a mistake, he added.
"It is fair to say the kinds of monies you would have to spend each year on dealing with climate change, in the sense of cutting back on emissions... at the moment looks quite small relative to the sums that we're having to put in to shore up the banking system."
Lord Stern, a former World Bank economist and currently chair of the Grantham Research Institute on Climate Change and the Environment at London School of Economics and Political Science, compiled the Stern Review into the Economics of Climate Change for the UK government in 2006.
It warned the world had to act immediately or face devastating economic consequences.