When scientists say the planet is warming, they usually point to rising air temperatures as proof. That’s reasonable enough, especially since the warmth of the air temperature affects us directly so we feel the change the scientists are measuring. But it’s also misleading: while the lower atmosphere has been gradually warming over the past 50 years, it happens unevenly, rising sharply for a year or two or even ten, then flattening out. That stutterstep pattern is due to relatively short-lived effects on top of the general warming – an El Nino current in the Pacific making things warmer, for example, or a volcanic eruption like 1991’s Mt. Pinatubo producing a cloud of dust that makes things cooler. Over time, these cancel out, but it can be tempting – though incorrect – to think a temporary flattening means global warming has stopped. To get a measure of what’s truly going on, scientists look to the oceans – slow to heat up, slow to cool down, and thus less prone to short-term variations. Indeed, says John Lyman an oceanographer at the University of Hawaii, ‘about 80 or 90 percent of the extra heat absorbed by the planet is absorbed into the […]