That is the conclusion of a major study commissioned by the British government that is due to be released today.
The 700-page study focuses on the economic -- not the environmental -- consequences of global warming, and is said to conclude that inaction could cost the world up to $7 trillion.
Prime Minister Tony Blair said today it is "the most important report on the future which I have received since becoming prime minister."
Combating climate change, the report says, will cost about 1 percent of global gross domestic product.
The report also calls for a successor to the Kyoto agreement on greenhouse gases to be signed next year -- not in 2010 or 2011, as planned -- because the problem is so urgent.
(compiled from agency reports)
View a photo gallery summarizing some key findings of the Stern report on the economic costs of global warming (epa)
THE STERN REPORT: In October, former World Bank chief economist Sir Nicholas Stern issued a 700-page report on the economic impact of global warming. The report, which was commissioned by the British government, estimates that climate change could cost between 5 and 20 percent of global GDP by the end of the century....(more)