Long weekend reading: Over at e360, Climate Central’s Michael Lemonick sums up the latest thinking on the big question of whether clouds will alleviate or accelerate global warming.
It’s no small detail. Just about everyone agrees that anthropogenic climate change will produce more cloud cover. The mystery is whether that in turn will produce a positive or negative feedback. Lemonick’s take-home message is that the evidence is beginning, just, to tilt in favor of the bad-news scenario.
And although researchers are still far from certain whether an anticipated increase in cloudiness will further heat up the planet or offset the warming a bit, a growing consensus among climate modelers is that clouds will increase, rather than hold back, the warming triggered by greenhouse gases. That’s largely because water vapor itself is a powerful greenhouse gas, which means that clouds should trap more heat than they are likely to reflect back into space.
Still, at this point, few climate scientists would be willing to stake their reputations on a definitive forecast of how clouds will impact the climate system in coming decades and centuries. Stanford University climate scientist Stephen Schneider, in an e-mail written just a week or so before his untimely death on July 19, said, “Cloud feedback has been uncertain by a factor of 3 since I did the first paper with that title nearly 40 years ago — we are still no closer to an answer.”