Human activities that spur global warming are largely to blame for changes in rainfall patterns over the last century, climate researchers reported Monday.
The report was released as record rains caused severe flooding in Britain, China and Indonesia.
Human-caused climate change has been responsible for higher air temperatures and hotter seas and is widely expected to lead to more droughts, wildfires and floods, but the authors say this is the first study to specifically link it to precipitation changes.
"For the first time, climate scientists have clearly detected the human fingerprint on changing global precipitation patterns over the past century," researchers from Environment Canada, that country's environmental agency, said in a statement.
The scientists, writing in the journal Nature, found humans contributed significantly to these changes, which include more rain and snow in northern regions that include Canada, Russia and Europe, drier conditions in the northern tropics and more rainfall in the southern tropics.
Manmade climate change has had a "detectable influence" on changes in average precipitation in these areas, and it cannot be explained by normal climate variations, they wrote.
Weather experts in Britain raised the possibility that the current rains there may be related to climate change.
"The global climate models indicate a future for the UK with drier summers and wetter winters, but storm events in the summer are predicted to be more frequent and more intense," David Butler of the University of Exeter said in a statement. "So it may well be the case that we will have to learn to live with more flooding.
Nick Reeves, executive director of the Chartered Institution of Water and Environmental Management in Britain, said that "extreme events such as we have seen in recent weeks herald the specter of climate change and it would be irresponsible to imagine that they won't become more frequent."
Numerous studies and reports by a panel of scientists convened by the United Nations have reported with increasing certainty that human activities — notably the burning of fossil fuels that emit greenhouse gases — have contributed to global warming in the last half-century and that the effects of this are already evident.
The U.N.'s Intergovernmental Panel on Climate Change estimated temperatures would rise 3.2 to 7.3 degrees Fahrenheit by the year 2100, leading to more hunger, water shortages and extinctions.
