Human activities are the prime reason the world’s oceans have slowly warmed over the past 40 years – a trend that will continue and will affect Western snowpack, California rainfall and other weather patterns, a new study concludes.
“Fifty years from now, it’s going to be several degrees warmer,” said Warren Washington, a climatologist at the National Center for Atmospheric Research in Boulder and a co-author of the report, published in today’s Science.
“We’re going to have major shifts in the precipitation zones,” Washington said.
The study comes less than two months after National Aeronautics and Space Administration researchers reported finding a “smoking gun” signal of global warming – Earth absorbing more heat than it released.
The new study is one of the most comprehensive analyses of the temperatures in the oceans, which absorb much of the planet’s heat.
Scientists collected detailed data on ocean temperatures across the globe, going back 40 years, and compared them with results generated by computer climate models.
Only when they included climate changes caused by people – the dumping of the greenhouse gas carbon dioxide into the atmosphere through fossil-fuel burning and other activities, and sulfate pollution – did they find a match between the real data and the models.
“It was a distinctive signal, and for the models to capture it so well is quite remarkable,” said co-author Tim Barnett of the Scripps Institution of Oceanography in La Jolla, Calif.
Barnett and his co-authors concluded that humans are changing ocean temperatures and that some computer climate models were so accurate in describing the current ocean conditions that they are probably just as good looking into the future.
And the future doesn’t look great for water in the West.
“If you consider the predictions for the West,” said David Pierce, a Scripps research and study co-author, “… it’s going to actually have a serious effect.”
“The temperature changes are enough to melt snowpack earlier in the year, and you’ll have more precipitation falling as rain than snow,” Pierce said.
While Roger Pielke Jr., director of the University of Colorado’s Center for Science and Technology Policy Research, said the new study is solid scientifically, he called it “deja vu.”
“My concern is that it doesn’t advance the policy debate,” Pielke said. He expects the new report to fuel yet another round of arguments between the majority of scientists who believe climate change is happening and the few who don’t.
Current policies proposed to deal with climate change – from the international Kyoto Protocol to reduce greenhouse- gas emissions to better fuel standards for cars – haven’t gained political traction in this country, he said.
Staff writer Katy Human can be reached at 303-820-1910 or khuman@denverpost.com.