UN: Global warming human-caused, may be irreversible

WASHINGTON -- Global warming is here, human-caused and likely already dangerous -- and it's increasingly likely the heating trend could be irreversible, a draft of a new international science report says.

The United Nations Intergovernmental Panel on Climate Change on Monday sent governments a final draft of its synthesis report, which combines three earlier, gigantic documents by the Nobel Prize-winning group. There is little in the report wasn't in the other more-detailed versions, but the language is more stark and the report attempts to connect the different scientific disciplines studying problems caused by the burning of fossil fuels, such as coal, oil and gas.

The 127-page draft, obtained by The Associated Press, paints a warning of what's causing global warming and what it will do to humans and the environment. It describes what can be done about it.

"Continued emission of greenhouse gases will cause further warming and long-lasting changes in all components of the climate system, increasing the likelihood of severe, pervasive and irreversible impacts for people and ecosystems," the report said.

The final report will be issued after governments and scientists go over the draft line by line in an October conference in Copenhagen.

Depending on circumstances and values, "currently observed impacts might already be considered dangerous," the report says. It mentions extreme weather and rising sea levels, such as heat waves, flooding and droughts.

It raises, as an earlier report did, the idea climate change will worsen violent conflicts and refugee problems and could hinder efforts to grow more food. And ocean acidification, which comes from the added carbon absorbed by oceans, will harm marine life, it says.

Without changes in greenhouse gas emissions, "climate change risks are likely to be high or very high by the end of the 21st century," the report says.

In 2009, countries across the globe set a goal of limiting global warming to about another 2 degrees Fahrenheit above current levels. But the report says that it is looking more likely that the world will shoot past that point. Limiting warming to that much is possible but would require dramatic and immediate cuts in carbon dioxide pollution.

The report says if the world continues to spew greenhouse gases at its accelerating rate, it's likely that by midcentury temperatures will increase by about another 3.6 degrees Fahrenheit (2 degrees Celsius) compared to temperatures from 1986 to 2005. And by the end of the century, that scenario will bring temperatures that are about 6.7 degrees warmer (3.7 degrees Celsius).

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Online:

Intergovernmental Panel on Climate Change: http://www.ipcc.ch/

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Seth Borenstein can be followed at http://twitter.com/borenbears