EU leaders agreed tough targets last month for reducing emissions of the gases that cause global warming, with the aim of limiting the rise in temperature to below two degrees Celsius, compared to pre-industrial levels.
The Intergovernmental Panel on Climate Change (IPCC), the UN's top expert authority on global warming, said in its report Friday that up to 30 percent of animal and plant species will be vulnerable to extinction if global temperatures rise by 1.5-2.5 C (2.7 F to 4.5 F).
"The report shows many of the serious impacts that would occur if global warming exceeded the EU's target of not more than two degrees Celsius above the pre-industrial level," European Environment Commissioner Stavros Dimas said.
"The temperature today is already almost 0.8 degrees Celcius above that level, so the world needs to act fast if we are to succeed in stabilizing climate change and thereby prevent its worst impacts," he said in a statement.
Global warming to hit Europe unevenly
The report predicted greenhouse gases would change rainfall patterns, intensify tropical storms, accelerate the melting of Arctic ice and mountain glaciers, and amplify the risk of drought, flooding and water stress.
Global warming will hit Europe hard but unevenly this century, cursing the south but giving a mixed blessing to the north, the report said. Mediterranean countries can brace for a higher risk of severe droughts, reduced harvests and deadly heat waves, while high-latitude nations will face flooding and severe weather balanced by longer growing seasons and expanded areas for agriculture and forestry.
"Today's IPCC report spells out very clearly the severe effects that climate change will have on all of us," Dimas said. "This further underlines both how urgent it is to reach global agreement on reducing greenhouse gas emissions and how important it is for us all to adapt to the climate change that is already under way," he said.
US, China try to dilute damning sections of report
However, the report -- the UN's most toughly-worded warning on climate change as yet -- was the subject of fierce disputes in Brussels between scientists and governments. Gary Yohe, one of the report's lead authors, told Reuters that the mood at the conference in Brussels was tense.
He said China, Russia and Saudi Arabia had raised most objections during the night to a 21-page summary which has to be approved unanimously and will guide policy in coming years on issues such as extending the U.N.'s Kyoto Protocol beyond 2012.
The United States was also reported to be among countries seeking to water down sections about damaging impacts from a warming widely blamed on human use of fossil fuels.
Some scientists objected, for instance, after China tried to eliminate a note saying that there was "very high confidence" that climate change was already affecting "many natural systems, on all continents and in some oceans."
China, the second largest source of greenhouse gases after the United States and ahead of Russia, wanted no mention of the level of confidence.
Poor countries most at risk
The report underlined that poor tropical countries will be hit worst. Worsening water shortages in thirsty countries, malnutrition caused by desiccated fields, property damage from extreme weather events and the spread of disease by mosquitoes and other vectors will amount to a punishing bill that is beyond the ability of vulnerable countries, especially in Africa, to pay.
"Poor people are the most vulnerable and will be the worst hit by the impacts of climate change. This becomes a global responsibility," IPCC's chairman, Rajendra Pachauri, said.
German Development Minister Heidemarie Wieczorek-Zeul repeated the warning in Brussels as she reminded western countries that they are responsible for most of the world’s climate change. She said they must do more to help poor countries who are the least responsible yet are most affected by it.
“Our production processes, the way we treat the environment and use our energy: these are a direct, ongoing attack on the basic foundations needed to sustain life," Wieczorek-Zeul said.
The German minister said industrial nations must do everything possible to protect such regions by lowering emissions. The minister suggested that since 20 to 25 percent of global warming can be traced back to the destruction of tropical rainforests, countries who maintain forests should receive financial assistance.
"I suggest, that we set up international financial mechanisms to compensate developing countries who maintain their forests because countries who do that, do something for the world climate, and they ought to be rewarded for their efforts."
Leading conservation groups on Friday urged an immediate global response to the damning UN report.
"The urgency of this report, presented by the world's top scientists, should be matched with an equally urgent response by governments," said Hans Verolme, director of the World Wildlife Fund's global climate change program.