Stick That In Your Climate Model...

...and fine-tune it.

Apparently, it's been know for awhile now that airborne bacterial streams could prompt precipitation in the form of rain or snow. The single-celled bodies which make up these streams serve as "nucleators" that water vapor can coalesce and freeze around. However, how ubiquitous these streams were, and how important they might be to cloud formation, has only recently become apparent:

"Atmospheric scientists haven't previously recognized that these particles are so widely distributed," [Louisiana State University microbiologist Brent Christner] said.

The findings raise the question of how climate change and human activities will affect bacterial balances in the sky. More immediately, they're a starting point for research on bacterial contributions to cloud formation and precipitation.

Since the impact of feedback loops involving clouds on global weather patterns is the largest source of uncertainty in current predictions of climate change, the new research should eventually allow for greater precision in these forecasts.

More cool cloud stuff here.

Climate Modelling Breakthrough?

From the .pdf to a Science magazine article behind their fire-wall:

Clouds have always given climate modelers fits. The clouds in their models are crude at best, and in the real world, researchers struggle to understand how clouds are responding to—and perhaps magnifying—greenhouse warming. As a result, cloud behavior is the biggest single source of uncertainty in climate prediction. But two new studies now show that much of the worry about clouds’ role in the warming has been misdirected. Clouds’ response to global temperature changes may be much quicker and more direct—and thus easier to study—than experts have thought.

[...]

“It’s a little bit of good news,” says climate researcher Brian Soden of the University of Miami in Florida. “People have been working on [the cloud problem] for 2 decades or more, and we haven’t done a lot to decrease the uncertainty. I’m a little more optimistic now about making progress on this problem.”

Researchers have always considered the cloud problem a matter of feedbacks. In a positive feedback, increasing greenhouse gases warm the surface, and the warmer surface then feeds back somehow to overlying clouds. The nature of the feedback remains mysterious, but if it’s positive, it would decrease global cloud cover. With fewer clouds reflecting solar energy back into space, more energy would reach Earth, amplifying the initial warming. But Earth’s surface and especially its oceans are slow to warm, so cloud feedbacks operate over decades—or so scientists assumed.

That's what they assumed. So what did they find?

Two groups have recently looked at just how quickly model clouds actually respond to an increase in greenhouse gases. Climate researchers Jonathan Gregory and Mark Webb, both of the Hadley Centre for Climate Prediction and Research in Exeter, U.K., report in the January Journal of Climate (issue 1) that model clouds, at least, can respond quickly to added carbon dioxide—in months, not decades. In most of the models examined, the classic cloud feedback driven by change at the surface played only a minor role. The real action took place where the clouds themselves were, up in the air. Added carbon dioxide absorbs more long-wave energy radiating from the surface; the air holding that carbon dioxide warms, and clouds evaporate, letting more solar radiation in.

These new studies, alongside of this result, will make it hard to be a Warmocaust Collusionist in 2008.

PS. I've got the .pdf of the Science article. If anyone wants the whole thing, leave a comment with an e-mail.