The world has pumped roughly 100 billion tons of carbon into the atmosphere over the past decade. But you wouldn’t know it by looking at global temperatures. The Economist, in a piece titled “Apocalypse Perhaps a Little Later,” quotes NASA’s James Hansen thusly: “The five-year mean global temperature has been flat for a decade.” What’s more, surface temperatures since 2005 are at the low end of the range of projections derived from 20 climate models, notes Ed Hawkins of the University of Reading. If temperatures remain flat for much longer, they’ll drop out of the models’ range entirely. The Economist:
The mismatch between rising greenhouse-gas emissions and not-rising temperatures is among the biggest puzzles in climate science just now. It does not mean global warming is a delusion. Flat though they are, temperatures in the first decade of the 21st century remain almost 1°C above their level in the first decade of the 20th. But the puzzle does need explaining.
The mismatch might mean that—for some unexplained reason—there has been a temporary lag between more carbon dioxide and higher temperatures in 2000-10. Or it might be that the 1990s, when temperatures were rising fast, was the anomalous period. Or, as an increasing body of research is suggesting, it may be that the climate is responding to higher concentrations of carbon dioxide in ways that had not been properly understood before. This possibility, if true, could have profound significance both for climate science and for environmental and social policy.
As it is, the worst-case climate change scenarios look less likely, which weakens the case for radical emissions reductions. But does this argue for doing nothing more than watchful waiting and adapting to the impacts that do occur? Maybe. Or should government ramp up spending on energy research and consider instituting a slow-ratcheting carbon tax that would a) replace energy regulation and subsidies and b) offset harmful labor and capital taxes. The magazine’s conclusion: “If the world has a bit more breathing space to deal with global warming, that will be good. But breathing space helps only if you actually do something with it.”