YOKOHAMA, Japan, March 31 (Reuters) - Global warming poses a mounting threat to the health, economic prospects, and food and water sources of billions of people, a report by top scientists said, in a call for urgent action to counter the effects of carbon emissions.
The latest report from the U.N. Intergovernmental Panel on Climate Change (IPCC), places an emphasis on the risks and may make the case for cutting greenhouse gas emissions clearer both to policymakers and the public by placing it in the category of an insurance policy for the planet.
"Climate change is really a challenge of managing risks," Christopher Field, co-chair of the IPCC group preparing the report, told Reuters before its release on Monday.
"One critical way is in decreasing the amount of climate change that occurs, and the other is finding a way to cope as effectively as we can with the climate changes that can't be avoided," Field said.
The time for action is now, according to the report, which follows an earlier assessment raising the probability that humans are responsible for global warming that is thought to cause droughts, colder weather and rising sea levels.
Many governments have pleaded for greater scientific certainty before making billion-dollar investments in everything from flood barriers to renewable energies.
The report, a draft of which was posted on a climate sceptical website "nofrakkingconsensus" in November, warns that parts of society and nature are more vulnerable than expected to climate change.
Atmospheric warming will exacerbate threats to health, damage yields of major crops in many areas and lead to more floods, the report says. It could also deepen poverty and worsen economic shocks that are at the heart of violent conflicts.
"We are here to remind world leaders like Barack Obama, Angela Merkel, David Cameron and many others that this is the time to act, cut emissions to fight climate change," Christian Teriete, communications director of the Global Call for Climate Action, said on Sunday at a gathering near the conference centre in Yokohama where the text of the report was finalized.
The IPCC's credibility is under extra scrutiny, after the panel's last report in 2007 wrongly exaggerated the melt of Himalayan glaciers. Several reviews said that this error, however, did not undermine the key findings in 2007.
The report is the second in a four-part IPCC assessment meant to guide governments that have promised to agree a pact in 2015 to slow climate change. The first, in September, raised the probability that most global warming is man-made to at least 95 percent from 90 in 2007.
Climate scientists say they are more certain than ever before that mankind is the main culprit for global warming and warned the impact of greenhouse gas emissions would linger for centuries.
The report is a compilation of the work of hundreds of scientists but sceptics, who challenge evidence for man-made climate change and question the need for urgent action, have become emboldened by the fact that temperatures have risen more slowly recently despite rising greenhouse gas emissions.
The IPCC report says that a warming trend is "unequivocal". And some effects would last far beyond the lifetimes of people now alive.
The report says that temperatures were likely to rise by between 0.3 and 4.8 degrees Celsius (0.5 to 8.6 Fahrenheit) by the late 21st century. The low end of the range would only be achieved if governments sharply cut greenhouse gas emissions.
And it said world sea levels could rise by between 26 and 82 cm (10 to 32 inches) by the late 21st century, driven up by melting ice and an expansion of water as it warms, in a threat to coastal cities from Shanghai to San Francisco.
(Reporting by Aaron Sheldrick and Chris Meyers; Editing by Richard Pullin)