The landmark Paris Agreement, signed by nearly every nation on Earth except the U.S., aims to keep the world’s temperature from rising to dangerous, climate-shifting levels of 2 degrees Celsius above pre-industrial levels.
Now, a new study finds that even the best-case scenario of "only" a 1-degree rise could increase the likelihood of extreme weather — including floods, droughts and heat waves — in the U.S. and around the world.
The frequency of extreme climate and weather events is already increasing, and many experts say man-made climate change is an important motivating factor.
"Damages from extreme weather and climate events have been increasing, and 2017 was the costliest year on record," said study lead author Noah Diffenbaugh of Stanford University. "These rising costs are one of many signs that we are not prepared for today's climate, let alone for another degree of global warming."
In 2017, three monster hurricanes and a ferocious wildfire season led to the costliest year for natural disasters on record in the U.S., with a damage cost of some $306 billion, according to the National Oceanic and Atmospheric Administration.
Keeping the world's temperature to a 1-degree Celsius (1.8 degrees Farenheit) rise is informally known as an "aspirational" target of the Paris Agreement, compared with the actual commitment of a 2-degree Celsius (3.6 degrees Fahrenheit) rise.
Another 2 to 3 degrees Celsuis of global warming would likely lead to three times as many record-breaking wet days across large chunks of the U.S., the study said.
More worrisome, several studies have found that even if every nation follows through on its pledges to cut greenhouse-gas emissions — already a big if — worldwide average temperatures would be likely to rise closer to 3 degrees Celsius (5.4 degrees Farenheit) this century, the Massachusetts Institute of Technology said.
While greater increases in the likelihood of extreme weather events would be reduced if the world achieves the Paris deal's aspirational target, "we still will be living in a climate that has substantially greater probability of unprecedented events than the one we're in now," Diffenbaugh said.
Previous studies from Diffenbaugh's team found global warming has increased the odds of the hottest events across more than 80% of the planet, while also increasing the likelihood of both wet and dry extremes.
The research appeared Wednesday in the peer-reviewed journal Science Advances, a publication of the American Association for the Advancement of Science.