YOKOHAMA, Japan (AP) — If the world doesn't cut pollution of heat-trapping gases, the already noticeable harms of global warming could spiral "out of control," the head of a United Nations scientific panel warned Monday.

And he's not alone. The Obama White House says it is taking this new report as a call for action, with Secretary of State John Kerry saying "the costs of inaction are catastrophic."

Rajendra Pachauri, chairman of the Intergovernmental Panel on Climate Change that issued the 32-volume, 2,610-page report here early Monday, told The Associated Press: "It is a call for action." Without reductions in emissions, he said, impacts from warming "could get out of control."

One of the study's authors, Maarten van Aalst, a top official at the International Federation of the Red Cross and Red Crescent Societies, said, "If we don't reduce greenhouse gases soon, risks will get out of hand. And the risks have already risen."

Twenty-first century disasters such as killer heat waves in Europe, wildfires in the United States, droughts in Australia and deadly flooding in Mozambique, Thailand and Pakistan highlight how vulnerable humanity is to extreme weather, according to the report from the Nobel Prize-winning group of scientists. The dangers are going to worsen as the climate changes even more, the report's authors said.

"We're now in an era where climate change isn't some kind of future hypothetical," said the overall lead author of the report, Chris Field of the Carnegie Institution for Science in California. "We live in an area where impacts from climate change are already widespread and consequential."

Nobody is immune, Pachauri and other scientists said.

"We're all sitting ducks," Princeton University professor Michael Oppenheimer, one of the main authors of the report, said in an interview.

After several days of late-night wrangling, more than 100 governments unanimously approved the scientist-written 49-page summary — which is aimed at world political leaders. The summary mentions the word "risk" an average of about 5 1/2 times per page.

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"Changes are occurring rapidly and they are sort of building up that risk," Field said.

These risks are both big and small, according to the report. They are now and in the future. They hit farmers and big cities. Some places will have too much water, some not enough, including drinking water. Other risks mentioned in the report involve the price and availability of food, and to a lesser and more qualified extent some diseases, financial costs and even world peace.

"Things are worse than we had predicted" in 2007, when the group of scientists last issued this type of report, said report co-author Saleemul Huq, director of the International Centre for Climate Change and Development at the Independent University in Bangladesh. "We are going to see more and more impacts, faster and sooner than we had anticipated."

The problems have gotten so bad that the panel had to add a new and dangerous level of risks. In 2007, the biggest risk level in one key summary graphic was "high" and colored blazing red. The latest report adds a new level, "very high," and colors it deep purple.

You might as well call it a "horrible" risk level, said van Aalst: "The horrible is something quite likely, and we won't be able to do anything about it."

The report predicts that the highest level of risk would first hit plants and animals, both on land and the acidifying oceans.

Climate change will worsen problems that society already has, such as poverty, sickness, violence and refugees, according to the report. And on the other end, it will act as a brake slowing down the benefits of a modernizing society, such as regular economic growth and more efficient crop production, it says.

"In recent decades, changes in climate have caused impacts on natural and human systems on all continents and across the oceans," the report says.

And if society doesn't change, the future looks even worse, it says: "Increasing magnitudes of warming increase the likelihood of severe, pervasive, and irreversible impacts."

While the problems from global warming will hit everyone in some way, the magnitude of the harm won't be equal, coming down harder on people who can least afford it, the report says. It will increase the gaps between the rich and poor, healthy and sick, young and old, and men and women, van Aalst said.

But the report's authors say this is not a modern day version of the Four Horsemen of the Apocalypse. Much of what they warn of are more nuanced troubles that grow by degrees and worsen other societal ills. The report also concedes that there are uncertainties in understanding and predicting future climate risks.

The report, the fifth on warming's impacts, includes risks to the ecosystems of the Earth, including a thawing Arctic, but it is far more oriented to what it means to people than past versions.

The report also notes that one major area of risk is that with increased warming, incredibly dramatic but ultra-rare single major climate events, sometimes called tipping points, become more possible with huge consequences for the globe. These are events like the melting of the Greenland ice sheet, which would take more than 1,000 years.

"I can't think of a better word for what it means to society than the word 'risk,'" said Virginia Burkett of the U.S. Geological Survey, one of the study's main authors. She calls global warming "maybe one of the greatest known risks we face."

Global warming is triggered by heat-trapping gases, such as carbon dioxide, that stay in the atmosphere for a century. Much of the gases still in the air and trapping heat came from the United States and other industrial nations. China is now by far the No. 1 carbon dioxide polluter, followed by the United States and India.

Unlike in past reports, where the scientists tried to limit examples of extremes to disasters that computer simulations can attribute partly to man-made warming, this version broadens what it looks at because it includes the larger issues of risk and vulnerability, van Aalst said.

Freaky storms like 2013's Typhoon Haiyan, 2012's Superstorm Sandy and 2008's ultra-deadly Cyclone Nargis may not have been caused by warming, but their fatal storm surges were augmented by climate change's ever rising seas, he said.

And in the cases of the big storms like Haiyan, Sandy and Hurricane Katrina in 2005, the poor were the most vulnerable, Oppenheimer and van Aalst said. The report talks about climate change helping create new pockets of poverty and "hotspots of hunger" even in richer countries, increasing inequality between rich and poor.

Report co-author Maggie Opondo of the University of Nairobi said that especially in places like Africa, climate change and extreme events mean "people are going to become more vulnerable to sinking deeper into poverty." And other study authors talked about the fairness issue with climate change.

"Rich people benefit from using all these fossil fuels," University of Sussex economist Richard Tol said. "Poorer people lose out."

Huq said he had hope because richer nations and people are being hit more, and "when it hits the rich, then it's a problem" and people start acting on it.

Part of the report talks about what can be done: reducing carbon pollution and adapting to and preparing for changing climates with smarter development.

The report echoes an earlier U.N. climate science panel that said if greenhouse gases continue to rise, the world is looking at another about 6 or 7 degrees Fahrenheit (3.5 or 4 degrees Celsius) of warming by 2100 instead of the international goal of not allowing temperatures to rise more than 2 degrees Fahrenheit (1.2 degrees Celsius). The difference between those two outcomes, Princeton's Oppenheimer said, "is the difference between driving on an icy road at 30 mph versus 90 mph. It's risky at 30, but deadly at 90."

Tol, who is in the minority of experts here, had his name removed from the summary because he found it "too alarmist," harping too much on risk.

But the panel vice chairman, Jean-Pascal van Ypersele, said that's not quite right: "We are pointing for reasons for alarm ... It's because the facts and the science and the data show that there are reasons to be alarmed. It's not because we're alarmist."

The report is based on more than 12,000 peer reviewed scientific studies. Michel Jarraud, secretary general of the World Meteorological Organization, a co-sponsor of the climate panel, said this report was "the most solid evidence you can get in any scientific discipline."

Michael Mann, a climate scientist at Pennsylvania State University who wasn't part of this report, said he found the report "very conservative" because it is based on only peer reviewed studies and has to be approved unanimously.

There is still time to adapt to some of the coming changes and reduce heat-trapping emissions, so it's not all bad, said study co-author Patricia Romero-Lankao of the National Center for Atmospheric Research in Colorado.

"We have a closing window of opportunity," she said. "We do have choices. We need to act now."

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Online:

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

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