The effects of global warming could spiral "out of control" if the world does not cut pollution of heat-trapping gases, a United Nations scientific panel has warned in a new report.
And the dangers of 21st 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 are going to increase, according to the report from a Nobel Prize-winning group of scientists.
A summary of the report, released by the Intergovernmental Panel on Climate Change on Monday, was unanimously approved by more than 100 governments.
"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 era where impacts from climate change are already widespread and consequential."
In recent decades, changes in climate have already caused impacts on natural and human systems on all continents and across the oceans, the report says. But if society does not change, the future looks even worse.
Dangerous levels of risk
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."
"Increasing magnitudes of warming increase the likelihood of severe, pervasive, and irreversible impacts," the report says.
The risks are both big and small, and now and in the future, according to the report. They hit farmers and big cities. Some places will have too much water, some not enough, including drinking water.
Other risks mentioned involve the price and availability of food, and to a lesser extent, some diseases, financial costs and even world peace.
The problems have worsened to an extent 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 coloured blazing red. The latest report adds a new level, "very high", and colours it deep purple.
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.
It will also act as a brake slowing down the benefits of a modernising society, such as regular economic growth and more efficient crop production, it says.
While the problems from global warming will hit everyone in some way, the magnitude of the harm will not 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.
"We are going to see more and more impacts, faster and sooner than we had anticipated," said report co-author Saleemul Huq, director of the International Centre for Climate Change and Development at the Independent University in Bangladesh.
"We're all sitting ducks," Princeton University professor Michael Oppenheimer, one of the main authors of the report, said in an interview.