Today's carbon-spewing power plants and vehicles won't raise the global temperature to dangerous levels by 2060 even if they're allowed to keep operating to the end of their normal lifespans, a new study predicts.
The bad news is that that prediction will only hold if we stop building additional carbon dioxide-emitting devices immediately, said the study published in Science Thursday.
Still, Damon Matthews, a climate scientist at Concordia University in Montreal, who co-authored the paper, feels the conclusions are optimistic because they counter the widely held belief that major climate change is already inevitable.
"Yes, climate change is inevitable, but that's because of the decisions that we're making," he said Thursday. "What types of technology we're currently building [are] going to make a big difference to the state of the future climate."
Climate scientists have long recognized that even if man-made carbon emissions stopped today, warming would continue for some time because of the "inertia" of the existing carbon dioxide in the atmosphere.
Steven Davis, a senior research associate at the Carnegie Institution for Science in Stanford, Calif., wanted to find out how much warming could arise from "technological inertia" — the future emissions of the cars, power plants and other emitters that are already built.
He did some research and managed to dig up the ages, average lifetimes and average emissions of power plants, vehicles and other carbon-emitting machines and facilities around the world.
Then Matthews plugged the data into a climate computer model and discovered that such existing emissions would push the temperature 1.3 degrees Celsius higher than pre-industrial temperatures.
0.7 degrees below threshold
That's about half a degree higher than the warming that's occurred so far. It's also 0.7 degrees lower than the two-degree temperature increase that many scientists consider the threshold for some of the more dangerous effects of global warming, such as a significant rise in sea levels.
Matthews said it's also "a big deal politically" because the focus of negotiations at the Copenhagen climate summit in 2009 had been to stay under the two-degree threshold.
However, Matthews acknowledged that there is always uncertainty in models that could result in errors. For example, scientists aren't sure exactly where the carbon emitted goes and exactly how global temperatures respond to increases in atmospheric carbon dioxide.
In any case, Matthews said, the biggest challenge right now technologically is what to replace CO2-emitting infrastructure with.
"There isn't a single obvious choice," he said.
He said he's interested in modeling what might work as a technological path toward zero emissions. "Is it wind? Is it solar? Is it all of the above?"
In the meantime, Davis cautioned against any policies that would encourage the lifetimes of existing infrastructure to be extended.