Paris, Feb 02: The world's paramount scientific authority on global warming is poised to issue a long-awaited report that would consolidate and amplify warnings about climate change.
The review by the UN's Intergovernmental Panel on Climate Change (IPCC) is the first in six years, taking into account the work of thousands of experts around the world.
Sources in Paris, where the IPCC's chief officials were to unveil the document at 0830 GMT after a four-day meeting, said the panel would give its most emphatic assessment yet that humans were interfering with the climate system.
Green campaigners said the report added a stinging whip of urgency for curbing fossil-fuel gases that trap solar heat and drive the warming machinery.
"The IPCC report scientifically confirms the extent of this man-made crisis already hitting people across the world, and makes bleak predictions for the future -- more intense storms, droughts and rising sea levels," said Friends of the Earth Europe's Jan Kowalzig.
"We can no longer afford to ignore growing and compelling warnings from the world's leading experts."
A draft of the IPCC's "summary for policymakers" said there was now more than 90-percent certainty that man-made greenhouse gases had caused most of the warming detected at Earth's surface over the past half-century.
It pointed to shrinking snow and ice cover, retreating permafrost, longer droughts and changed precipitation patterns as proof that the climate had already been affected over the past two decades or longer.
Looking at the future, the IPCC would finetune a prediction of the rise in temperatures and sea levels by 2100.
Depending on the level of carbon dioxide (CO2) in the atmosphere, Earth's surface will have warmed by between 1.1 and 6.4 C (2.52 and 11.52 F), compared with concentrations at the end of the 20th century, the draft said.
Within that range, the likely rise is between 1.8 and 4.0 C (3.24 and 7.2 F), it said.
In 2001, using a somewhat different method of calculation, the IPCC gave a range of between 1.4 and 5.8 C.
Warming will cause sea levels to rise by between 28 and 58 centimetres (11.2-23.2 inches), the document would say. In the 2001 report, the estimate was nine to 88 cms (3.5-35 inches). The changed forecast is because of better knowledge about how the oceans absorb heat.
Warming is bound to stoke heatwaves, heavy rainfall and affect typhoons and hurricanes, the draft adds.
The IPCC, which comprises scientific and government representatives, is barely visible to the general public but carries significant clout because of its neutral and unvarnished portrayal of the facts.
Its reports have led to major changes in government policies and corporate strategies about carbon pollution, and also influenced individual lifestyles.
Friday's report is focused on the scientific evidence for global warming.
Two more reports, one on the socio-economic impacts of climate change and the other on attempts to mitigate them, will be issued at IPCC meetings in April.
At the end of an arduous process of selection and debate, they will be put in a synthesis report in November.