The U.N. climate panel issued its strongest warning yet on Friday that human activities are heating the planet, adding pressure on governments to do more to combat accelerating global warming.
The IPCC, the most authoritative group on warming grouping 2,500 scientists from more than 130 nations, predicted more severe rains, melting glaciers, droughts, heatwaves and rising sea levels, especially if Antarctica or Greenland thaw.
The final text said it was "very likely" -- or a probability of more than 90 percent -- that human activities led by burning fossil fuels explained most of the warming in the past 50 years.
That is a toughening from the last report, in 2001, when the IPCC said the link was "likely", or 66 percent probable. Signs of change range from drought in Australia to record high January temperatures in Europe.
"February 2, 2007 may be remembered as the day the question mark was removed from whether (people) are to blame for climate change," Achim Steiner, the head of the U.N. Environment Program, told a news conference.
He urged governments to inject more momentum into stalled talks on long-term cuts in emissions. Greenhouse gas levels in the atmosphere have not been higher in 650,000 years.
"We are in a sense doing things that have not happened in 650,000 years, based on the scientific evidence," Rajendra Pachauri, the head of the IPCC, told a news conference.
A 21-page summary of scientific findings for policy makers outlines wrenching change such as a possible melting of Arctic sea ice in summers by 2100 and says it is "more likely than not" that greenhouse gases have made tropical cyclones more intense.
The report predicts a "best estimate" that temperatures would rise by between 1.8 and 4.0 Celsius (3.2 and 7.8 Fahrenheit) in the 21st century, within a likely range from 1.1 to 6.4 Celsius.
Temperatures rose 0.7 degrees in the 20th century and the 10 hottest years since records began in the 1850s have been since 1994.
U.N. officials hope the report will prompt governments -- led by the United States, the top emitter -- and companies to do more to cut greenhouse gases, released mainly by burning fossil fuels in power plants, factories and cars.
CORAL ATOLLS
Many backers of the U.N.'s Kyoto Protocol, a plan binding 35 industrial nations to cut emissions of greenhouse gases by 2012, want outsiders to get more involved. The United States and China are not bound by Kyoto targets.
The head of the U.S. delegation said that President George W. Bush's policies, braking the rise of emissions rather than cutting them, were working.
"The President has put in place a comprehensive set of policies to address what he has called the 'serious challenge' of climate change," Sharon Hays, Associate Director of the White House Office of Science & Technology Policy, told Reuters.
Bush pulled out of Kyoto in 2001, saying caps would harm the economy and that Kyoto unfairly omitted developing nations from a first period to 2012. He focuses instead on big investments in technologies such as hydrogen and biofuels.
The President of Kiribati, a group of 33 Pacific coral atolls threatened by rising seas, said time was running out.
"The question is, what can we do now? There's very little we can do about arresting the process," President Anote Tong said.
The report projects a rise in sea levels of between 18 and 59 centimeters (7 and 23 inches) in the 21st century -- and said that bigger gains could not be ruled out if ice sheets in Antarctica and Greenland thaw.
Some leading scientists had criticized an earlier draft for cutting the range after the 2001 forecast a rise between 9 and 88 cms by 2100. Rising seas threaten countries such as Kiribati and cities from Shanghai to Buenos Aires.
(Reuters, 02/02/2007)