Two degrees. Policy makers around the world have long seen that figure as a sort of climate change safety zone. Prevent global average temperatures from rising more than 2° Celsius, the thinking goes, and we should be fine.
But in a commentary published this week in the journal Nature, a pair of San Diego researchers argue temperature rise may not be the best way to measure whether we're doing enough to combat climate change.
"Two degrees looked like a really great goal," said Charles Kennel, former director of the Scripps Institution of Oceanography. "Everybody could understand it. The public understands the term 'warming.'"
But Kennel and his co-author — UC San Diego international relations professor David Victor — have come to believe the two degree goal is politically misguided and ultimately unachievable.
Fixating on temperature can be misleading, Kennel argues, because there's been a pause in warming recently. Average temperatures have actually stayed flat over the last 16 years, because heat is being trapped in the ocean.
Kennel predicts rising temperatures will rebound in the future, and says today's temporary warming hiatus can lull leaders into a false sense of security. He suggests policy makers start focusing on other symptoms to understand what ails the planet.
"When you go to the doctor and get a check-up, you get your vital signs taken, one of which is the temperature. But the doctor looks at a lot of other things because your body is a complicated system. Climate scientists — doctors for the planet — look at a lot of things too, because the climate is a complicated system."
Kennel says for now, indicators like ocean heat content and the concentration of carbon dioxide in the atmosphere offer better climate vital signs than temperature.
Kennel worries climate change deniers will take this argument as an admission that global warming predictions haven't come to pass. "They'll probably say we moved the goalposts," he admits. And he knows the public won't grasp heat trapped in the ocean or carbon concentrated in the atmosphere as intuitively as they've grasped spikes in global temperature.
But after analyzing the science behind the two degree goal and sizing up its political outcomes, Kennel and Victor conclude, "New goals are needed."
