Science Now, BBC, Dot Earth: Scratch off one climate worry? Ocean conveyor belt of global currents is holding up just fine.
Well whew. Word in the past week, not circulated (pun intended) too widely but out there, provides some reassurance against long-discussed concerns that a warming, freshening North Atlantic will choke the currents that drive oceanic dynamics worldwide. It’s not that the the ocean is not getting a bit warmer, or that ice melt is not putting extra fresh, lower-density water in the sea that could upset the dynamics. It is simply that this thermohaline circulation, as it is often known in the journals, is not showing any overt sign of slowing down.
Among the more recent accounts is out today, from BBC‘s Richard Black, who reports that a recent series of encouraging reports got further cement from a team at NASA’s Jet Propulsion Lab. Its analysis of satellite data going back many years concurs that the circulation varies from time to time, but has no long-term trend.
That report came out last week in the journal Geophysical Research Letters, with writeups appearing a few days ago at several outlets. These include, at AAAS ScienceNOW a report from veteran Earth sciences man Richard Kerr, and at the NYTimes‘s Dot Earth blog site from its former reporter Andrew C. Revkin.
There ought to be no new “ThermohalineGate,” to join the other putative scandals in climate science, off this news. The case for a major risk of conveyor belt shut down has never been embraced by major review organizations, including the IPCC (which three years ago downgraded its already tepid worries). But the hypothesis has gotten deep attention in the press – and encouraged a few over-imaginative reporters to propose it would bring another ice age to Europe even while, perhaps, the Earth’s average temperature rises.
Such surmises made this a popular topic among journalists. Kerr’s report dates the scare headlines to 2005 when a Nature paper suggested a 30 percent decline in northward flow of the conveyor belt since the late 1950s. But I know the general meme goes back much farther than that. I don’t think I need to return it, but in my office is a plaque from the American Geophysical Union. I got it for a story that ran in US News & World Report in 2002 under the nice and balanced and careful hed Perilous Waters. I just re-read it. It’s well-couched in qualifiers. It expressly says that even with a rearrangement in ocean currents, no glaciers are going to slide down from Scandinavia. I reported however that a recent influx of fresh water at Greenland’s latitude had been measured. Nobody knows, I wrote, if it is “a natural climate cycle, global warming due to human activity, or some mix of the two,” and nobody could say whether it might be enough to push the currents toward collapse either.
But still, the story had that edge of possible calamity. And much as it was illogical, it left a conscienceless part of me sort of rooting for more signs of a conveyor belt in trouble. That’s perverse – and an illustration why objective reporters have to force themselves to stay professionally disinterested no matter how much their crasser instincts want them to go down in history as far-seeing prophets who had sounded the bell.
- Charlie Petit
