BRUSSELS, Belgium - As the world gets hotter by degrees, millions of poor people will suffer from hunger, thirst, floods and disease unless drastic action is taken, scientists and diplomats warned Friday in their bleakest report ever on global warming.
All regions of the world will change, with the risk that nearly a third of the Earth's species will vanish if global temperatures rise just 3.6 degrees above the average temperature in the 1980s-90s, the new climate report says. Areas that now have too little rain will become drier.
Yet that grim and still preventable future is a toned-down prediction, a compromise brokered in a fierce, around-the-clock debate among scientists and bureaucrats. Officials from some governments, including China and Saudi Arabia, managed to win some weakened wording.
Even so, the final report "will send a very, very clear signal" to governments, said Yvo de Boer, the top climate official for the United Nations, which in 1988 created the authoritative climate change panel that issued the starkly worded document.
And while some scientists were angered at losing some ground, many praised the report as the strongest warning ever that nations must cut back on greenhouse gas emissions.
The report is the second of four coming this year from the Intergovernmental Panel on Climate Change, a United Nations network of 2,000 scientists.
The new document tries to explain how global warming is changing life on Earth; the panel's report in February focused on the cause of global warming and said scientists are highly confident most of it is due to human activity.
All four reports must be unanimously approved by the 120-plus governments that participate, and all changes must be approved by the scientists.
That edict made for a deadline-busting contentious final editing session that was closed to the public. However, The Associated Press witnessed the hectic final 3Â½ hours of objections and conflict.
At one point, Chinese and Saudi Arabian delegates tried to reduce the scientific confidence level about already noticeable effects of global warming. They lower the confidence level from 90 percent to 80 percent. Scientists objected, and one lead author from the United States, NASA's Cynthia Rosenzweig, left the building after filing an official protest.
"There is a discernible human influence on these changes" that are already occurring through flooding, heat waves, hurricanes and threats to species, she said.
Under a U.S.-proposed compromise, the final report deleted any mention of the level of confidence about global warming's current effects. And that may have saved the day, according to some scientists who said the report had appeared doomed over that issue.
There were other disputes where scientists lost out:
•Instead of saying "hundreds of millions" would be vulnerable to flooding under certain scenarios, the final document says "many millions."
•Instead of suggesting up to 120 million people are at risk of hunger because of global warming, the revised report refers to negative effects on subsidence farmers and fishers.
Often it was the U.S. delegation who stood with scientists and helped reach compromise, said Stanford University scientist Stephen Schneider, a frequent critic of the Bush administration's global warming policies.
British scientist Neil Adger said he and others were disappointed that government officials deleted parts of a chart that highlights the devastating effects of climate change with every rise of 1.8 degrees in temperature.
Some scientists bitterly vowed never to take part in the process again. Still, Adger and other scientists and even environmental groups hailed the final report as the strongest ever.
"This is a glimpse into an apocalyptic future," the Greenpeace environmental group said of the final report.
The tone of the report is urgent, noting those who can afford the least get hit the most by global warming.
"Don't be poor in a hot country, don't live in hurricane alley, watch out about being on the coasts or in the Arctic, and it's a bad idea to be on high mountains with glaciers melting," said Schneider, the Stanford scientist who was one of the study author's.
Africa by 2020 is looking at an additional 75 million to 250 million people going thirsty because of climate change, the report said. Deadly diarrheal diseases associated with floods and droughts will increase in Asia because of global warming, the report said.
The first few degrees increase in global temperature will actually raise global food supply, but then it will plummet, according to the report. "The poorest of the poor in the world - and this includes poor people in prosperous societies - are going to be the worst hit," said Rajendra Pachauri, chairman of the Intergovernmental Panel on Climate Change. "People who are poor are least able to adapt to climate change." But even rich countries, such as the United States say that the report tells them what to watch for. James Connaughton, the head of the White House Council on Environmental Quality noted that food production in North America would rise initially, but so will increased coastal flooding. The head of the U.S. delegation, White House associate science adviser Sharon Hays, said a key message she's taking home to Washington is "that these projected impacts are expected to get more pronounced at higher temperatures," she said in a conference call from Brussels. "Not all projected impacts are negative." Schneider said a main message isn't just what will happen, but what already has started: melting glaciers, stronger hurricanes, deadlier heat waves, and disappearing or moving species. It all can be traced directly to greenhouse gases from the burning of fossil fuels, according to the report. Martin Parry, who conducted the tough closed-door negotiations, said that with 29,000 sets of data from every continent include Antarctica, the report firmly and finally established "a man-made climate signal coming through on plants, water and ice." "For the first time, we are not just arm-waving with models," he said. But many of the worst effects aren't locked into the future, the report said in its final pages. People can build better structures, adapt to future warming threats and reduce greenhouse gas emissions, scientists said. "There are things that can be done now, but it's much better if it can be done now rather than later," said David Karoly of the University of Oklahoma, one of the report authors. "We can fix this," Schneider said. (AP) On the Net: The Intergovernmental Panel on Climate Change: http://www.ipcc.ch/ The summary of the report: http://www.ipcc.ch/SPM6avr07.pdf (AP) AP Correspondent Arthur Max contributed to this report. AP-CS-04-06-07 1712EDT