The worst-case scenario envisaged by the report was as terrifying as created in doomsday films, said UN Secretary-General Ban Ki-moon.
"These scenes are as frightening as a science fiction movie," he said. "But they are even more terrifying, because they are real."
The 23-page document by the UN-backed panel of scientists, issued Saturday, Nov. 17, contained the strongest warnings yet on climate change and "answered many of our questions on climate change," the secretary general said.
New ethic required
IPCC Chairman Rajendra Pachauri pointed out several findings, including the threat rising sea levels posed to small island nations and hundreds of millions of people living in low-lying deltas as well as more infectious diseases and the destruction of coral reefs.
"We need a new ethic by which every human being realizes the importance of the challenge we are facing and starts to take action through changes in lifestyle and attitude," he said. "Every country in the world has to be committed to a shared vision and a set of common goals and actions that will help us move toward a much lower level of emissions."
Ban added that the international community would now have to "transform" its way of doing things in order to save the "treasure of our planet."
The final report of the Intergovernmental Panel on Climate Change is essentially a summary of three reports compiled by more than 2,000 scientists and issued by the IPCC earlier this year.
EU Environment Commissioner Stavros Dimas said the report was "a milestone in our scientific knowledge about climate change and the grave threats global warming poses to the planet."
"The report's findings amount to a stark warning that the world must act fast to slash greenhouse gas emissions if we are to prevent climate change from reaching devastating levels," he said in a statement. "The good news is that it also shows that deep emission cuts are both technologically feasible and economically affordable."
Basis for Bali conference
Governments haggled for five days over the wording of this final IPCC document, which environmentalists say will serve as a manual on how to tackle global warming and set the tone for a crucial UN climate conference in Bali, Indonesia next month.
"We cannot afford to leave Bali without such a breakthrough," Ban said, referring to a conference running on the Indonesian island from Dec. 3-14, tasked with setting a strategy for deepening cuts in greenhouse-gas emissions.
Government representatives at the Bali conference are expected to negotiate a successor agreement to the Kyoto Protocol, which requires industrialized countries to make targeted commitments on curbing their greenhouse gases and expires in 2012.
The new IPCC report makes clear that global warming is a man-made phenomenon and is already taking place. It warns of catastrophic and unavoidable consequences if the atmosphere warms by more than 2 degrees Celsius (3.6 degrees F). Global temperatures have already risen about 0.7 degrees Celsius over the last 100 years.
Global warming can only be slowed
To prevent that, the level of carbon dioxide in the world's atmosphere must start dropping by 2020. By 2050, global emissions must be 50 percent to 65 percent below 2000 levels. The IPCC has already said global warming cannot be stopped, only slowed.
Melting glaciers and loss of snow in Alpine regions as well as thinning Arctic summer sea ice and thawing permafrost shows that climate change is already on the march, the IPCC report said.
Some of the newer elements of the report include one combined graphic that at a glance lays out specifically what levels of greenhouse gases lead to what rises in temperatures -- and what consequences each temperature rise could have on society.
Environmental groups pleased
Representatives from environmental protection groups appeared pleased with the study's results.
"The strong message of the IPCC can't be watered down -- the science is crystal clear," said Hans Verolme, director of environmental group WWF's Global Climate Change Program. "The hard fact is we have caused climate change, and it's also clear that we hold the solution to stop global warming in our hands,"
The IPCC was last month awarded the Nobel Peace Prize, along with former US Vice President Al Gore, for raising awareness of the threat of climate change.