 The poor are among those likely to suffer most from climate change, according to a draft UN report that says the world must act quickly to brake ever more damaging temperature rises. World leaders will meet at UN headquarters in New York on Monday to discuss ways to fight warming, partly spurred by reports by the UN climate panel early this year saying human activities were very likely the cause of an unequivocal warming. A new draft of the panel's 22-page "Summary for Policymakers", obtained by Reuters, sharpens warnings about climate change and adds a more human touch by pointing more clearly to those who are most vulnerable. "In all regions there are certain sectors and communities which are particularly at risk, for example the poor, young children, the elderly and the ill," it says. The report, prepared by 40 experts, sums up 3,000 pages of science. The poor, for instance, depend heavily on farming that may be disrupted by shifts in rains or desertification in Africa. In Asia, millions of the poorest people live around river deltas that may be hit by rising seas or storm surges. The report also highlights risks including extinctions, heatwaves, erosion and increased strain on water supplies for hundreds of millions of people. The draft of the report by the Intergovernmental Panel on Climate Change (IPCC), dated Aug. 31, will be reviewed and approved by governments in Valencia, Spain, in November. It updates a May 15 draft, obtained by Reuters last month. It reiterates that world emissions of greenhouse gases would have to peak by 2015 and then fall by between 50 and 85 percent by 2050 below 2000 levels to limit global temperature rise to 2.0-2.4 degrees Celsius (3.6-4.3 F) above pre-industrial times. Such curbs are far stiffer than those under consideration by most nations meeting in New York. President George W. Bush has also called talks of major emitters on Sept. 27-28. Even so, costs of slowing climate change would be moderate. Depending on the stiffness of curbs, the draft says costs of action would range from cuts in global gross domestic product of less than -0.12 to less than 0.06 percentage points a year. It warns that change is already emerging, ranging from earlier spring plantings of crops in some areas, more fires and pests in forests or a melting of low level ski resorts. Among editing changes, the new draft adds a mention that carbon dioxide, the main greenhouse gas emitted by burning fossil fuels, is at its highest level in at least 650,000 years. The main thrust of the report remains. "Warming of the climate system is unequivocal," it begins, noting that 11 of the past 12 years rank among the top dozen warmest years since records began in the 1850s. The report also shows that temperatures will rise by between 1.1 and 6.4 Celsius (2-12 Fahrenheit) this century and that sea levels are set to rise by 18 to 59 centimetres (7 to 23 inches) despite wide uncertainties about Greenland or Antarctica. The report does not add new information about a shrinking of Arctic sea ice this summer, saying the ice could disppear "almost entirely by the latter part of the 21st century". The US National Snow and Ice Data Center said in April that the melting was faster than projected by the IPCC and that the Arctic Ocean might be ice-free before the middle of the century.