It’s hard to sea, but the globe is still warming

Evidence of climate change is all around us, manifesting in superstorms, wildfires, and melting ice. But temperature spikes recorded by weather stations over the past 15 years have been more muted than was previously the case, and lower than climate models had predicted.

That’s leading many people to wonder: Is global warming less of a threat than we had feared?

Climate scientists have been noting for years that the atmosphere is heating up less quickly than expected. Since last year, a growing number have been suggesting that we adjust our warming projections downward. Just last week, 17 scientists called for exactly that in a letter published in the journal Nature Geoscience; they wrote that their latest projections for rising temperatures remain “in agreement with earlier estimates, within the limits of uncertainty,” but at the lower end of that range.

At issue is “climate sensitivity” — the extent to which temperatures warm as carbon dioxide levels rise. And central to the debate is “equilibrium climate sensitivity” — the temperature response to a doubling of carbon dioxide concentration in the atmosphere. (The CO2 concentration has already risen more than 40 percent since the industrial revolution, from about 280 parts per million to 400 ppm this month. And it is projected to nearly double the preindustrial level by 2050 — and then keep on rising.)

In its 2007 report, the Intergovernmental Panel on Climate Change projected that global average temperatures would rise by between 1 and 3 degrees Celsius once carbon dioxide levels doubled. The Nature Geoscience letter suggests that the rise would probably be between 0.9 and 2 degrees C, most likely 1.3 degrees. That 1.3 figure is lower than earlier most-likely projections, such as the IPCC’s, which suggested that an increase between 1.4 and 1.6 degrees C was most probable.

Phew! Everything is fine then, according to some sloppy news reports and optimistic headlines, which have suggested that such findings mean climate change isn’t such a daunting problem. It’s perhaps more comforting for the press to dwell on the minutiae of garden-variety scientific uncertainty than to consider the role of climate change in triggering droughts, floods, and killer storms.

Meanwhile climate skeptics have seized on the controversy and used it to bash climate science across the board.

As far back as 2009, some scientists were reporting [PDF] that the rise of land and sea surface temperatures had slowed down. But the flurry of more recent research and media attention has brought the controversy out of labs and into the limelight. Now people want to know: Where’s the missing heat?

Continues at Grist …

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