The world cannot afford to wait before tackling climate change, the UK prime minister has warned.
A report by economist Sir Nicholas Stern suggests that global warming could shrink the global economy by 20%.
But taking action now would cost just 1% of global gross domestic product, the 700-page study says.
Tony Blair said the Stern Review showed that scientific evidence of global warming was "overwhelming" and its consequences "disastrous".
The review coincides with the release of new data by the United Nations showing an upward trend in emission of greenhouse gases - a development for which Sir Nicholas said that rich countries must shoulder most of the responsibility.
And Chancellor Gordon Brown promised the UK would lead the international response to tackle climate change.
The BBC's Nick Robinson said that, while the Stern Review did not recommend specific tax rises, upping the cost of flying - both people and goods - and driving was on the agenda of all three main political parties.
Environment Secretary David Miliband said the Queen's Speech would now feature a climate bill to establish an independent Carbon Committee to "work with government to reduce emissions over time and across the economy".
The report says that without action, up to 200 million people could become refugees as their homes are hit by drought or flood.
"Whilst there is much more we need to understand - both in science and economics - we know enough now to be clear about the magnitude of the risks, the timescale for action and how to act effectively," Sir Nicholas said.
"That's why I'm optimistic - having done this review - that we have the time and knowledge to act. But only if we act internationally, strongly and urgently."
Mr Blair said the consequences for the planet of inaction were "literally disastrous".
"This disaster is not set to happen in some science fiction future many years ahead, but in our lifetime," he said.
"Investment now will pay us back many times in the future, not just environmentally but economically as well."
"For every £1 invested now we can save £5, or possibly more, by acting now.
"We can't wait the five years it took to negotiate Kyoto - we simply don't have the time. We accept we have to go further (than Kyoto)."
Sir Nicholas, a former chief economist of the World Bank, told BBC Radio 4's Today programme: "Unless it's international, we will not make the reductions on the scale which will be required."
He went on: "What we have shown is the magnitude of these risks is very large and has to be taken into account in the kind of investments the world makes today and the consumption patterns it has."
The Stern Review forecasts that 1% of global gross domestic product (GDP) must be spent on tackling climate change immediately.
It warns that if no action is taken:
- Floods from rising sea levels could displace up to 100 million people
- Melting glaciers could cause water shortages for 1 in 6 of the world's population
- Wildlife will be harmed; at worst up to 40% of species could become extinct
- Droughts may create tens or even hundreds of millions of "climate refugees"
The study is the first major contribution to the global warming debate by an economist, rather than an environmental scientist.
Mr Brown, who commissioned the report, has also recruited former US Vice-President Al Gore as an environment adviser.
"In the 20th century our national economic ambitions were the twin objectives of achieving stable economic growth and full employment," Mr Brown said.
"Now in the 21st century our new objectives are clear, they are threefold: growth, full employment and environmental care."
He said the green challenge was also an opportunity "for new markets, for new jobs, new technologies, new exports where companies, universities and social enterprises in Britain can lead the world".
"And then there is the greatest opportunity of all, the prize of securing and safeguarding the planet for our generations to come."
Mr Brown called for a long-term framework of a worldwide carbon market that would lead to "a low-carbon global economy". Among his plans are:
- Reducing European-wide emissions by 30% by 2020, and at least 60% by 2050
- By 2010, having 5% of all UK vehicles running on biofuels
- Creating an independent environmental authority to work with the government
- Establishing trade links with Brazil, Papua New Guinea and Costa Rica to ensure sustainable forestry
- Working with China on clean coal technologies
The review was welcomed by groups including the European Commission and business group the CBI.
"Provided we act with sufficient speed, we will not have to make a choice between averting climate change and promoting growth and investment," said CBI head Richard Lambert.
Pia Hansen, of the European Commission, said the report "clearly makes a case for action".
"Climate change is not a problem that Europe can afford to put into the 'too difficult' pile," she said.
"It is not an option to wait and see, and we must act now."