f 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.

“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.

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