The Earth faces increased hunger and water shortages in the poorest countries, massive floods and avalanches in Asia and species extinction unless nations adapt to climate change and halt its progress, according to a report approved Friday by an international conference on global warming.

Agreement came after an all-night session during which key sections were deleted from the draft and scientists angrily confronted government negotiators who they feared were watering down their findings.

"It has been a complex exercise," said Rajendra Pachauri, chairman of the Intergovernmental Panel on Climate Change.

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Several scientists objected to the editing of the final draft by government negotiators but in the end agreed to compromises. However, some scientists vowed never to take part in the process again.

The climax of five days of negotiations was reached when the delegates removed parts of a key chart highlighting devastating effects of climate change that kick in with every rise of 1.8 degrees, and in a tussle over the level of scientific reliability attached to key statements.

There was little doubt about the science, which was based on 29,000 sets of data, much of it collected in the past five years. "For the first time we are not just arm-waving with models," Martin Parry, who conducted the grueling negotiations, told reporters.

The United States, China and Saudi Arabia raised many of the objections to the phrasing, often seeking to tone down the certainty of some of the more dire projections.

The final IPCC report is the clearest and most comprehensive scientific statement to date on the impact of global warming mainly caused by man-induced carbon dioxide pollution.

"The poorest of the poor in the world — and this includes poor people in prosperous societies _ are going to be the worst hit," said Pachauri. "People who are poor are least able to adapt to climate change."

The report said up to 30 percent of the Earth's species face an increased risk of vanishing if global temperatures rise 3.6 degrees Fahrenheit above the average in the 1980s and 1990s.

Areas that now suffer a shortage of rain will become even drier, adding to the risks of hunger and disease, it said. The world will face heightened threats of flooding, severe storms and the erosion of coastlines.

"This is a glimpse into an apocalyptic future," the Greenpeace environmental group said of the final report.

Without taking action to curb carbon emissions, man's livable habitat will shrink starkly, said Stanford scientist Stephen Schneider, one of the authors. "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," he said.

"We can fix this," by investing a small part of the world's economic growth rate, said Schneider. "It's trillions of dollars, but it's a very trivial thing."

Negotiators pored over the 21-page draft meant to be a policy guide for governments. The summary pares down the full 1,572-page scientific assessment of the evidence of climate change so far, and the impact it will have on the Earth's most vulnerable people and ecosystems.

More than 120 nations attended the meeting. Each word was approved by consensus, and any change had to be approved by the scientists who drew up that section of the report.

Though weakened by the deletion of some elements, the final report "will send a very, very clear signal" to governments, said Yvo de Boer, the U.N.'s top climate official.

The summary will be presented to the G-8 summit of the world's richest nations in June, when the European Union is expected to renew appeals to U.S. President George W. Bush to join in international efforts to control emissions of fossil fuels.

This year's series of reports by the IPCC were the first in six years from the prestigious body of some 2,500 scientists, formed in 1988. Public awareness of climate change gave the IPCC's work unaccustomed importance and fueled the intensity of the closed-door negotiations during the five-day meeting.

"The urgency of this report prepared by the world's top scientists should be matched by an equally urgent response from governments," said Hans Verolme, director of the global climate change program of the World Wide Fund for Nature.

"Doing nothing is not an option," he said.

During the final session, the conference snagged over a sentence that said the impact of climate change already were being observed on every continent and in most oceans.

"There is very high confidence that many natural systems are being affected by regional climate changes, particularly temperature increases," said the statement on the first page of text.

But China insisted on striking the word "very," injecting a measure of doubt into what the scientists argued were indisputable observations. The report's three authors refused to go along with the change, resulting in an hours-long deadlock that was broken by a U.S. compromise to delete any reference to confidence levels.

It is the second of four reports from the IPCC this year; the first report in February laid out the scientific case for how global warming is happening. This second report explains what the effects of global warming will be.

European Environment Commissioner Stavros Dimas said the report will spur the EU's determination to curb greenhouse gas emissions.

"The world needs to act fast if we are to succeed in stabilizing climate change and thereby prevent its worst impacts," Dimas said in a statement.

For the first time, the scientists broke down their predictions into regions, and forecast that climate change will affect billions of people.

Africa will be hardest hit. By 2020, up to 250 million people are likely to be exposed to water shortages. In some countries, food production could fall by half, it said.

North America will experience more severe storms with human and economic loss, and cultural and social disruptions. It can expect more hurricanes, floods, droughts, heat waves and wildfires, it said.

Parts of Asia are threatened with massive flooding and avalanches from melting Himalayan glaciers. Europe also will see its Alpine glaciers disappear. Australia's Great Barrier Reef will lose much of its coral to bleaching from even moderate increases in sea temperatures, the report said.