Science - Breakthrough In Cloud Modeling Suggests Negative Climate Feedback "Very Unlikely"

[hatrack]

Clouds will respond to climate change in ways that further heat the planet, a new study suggests. The research, published yesterday in the journal Science, appears to solve one of of the biggest remaining mysteries in climate science: How well do computer climate models predict the behavior of clouds?

EDIT

"Clouds are really, I would say, the biggest uncertainty in understanding how much warming we're going to get in the future," said study author Andrew Dessler, an atmospheric scientist at Texas A&M University. "And up until my paper, all we really had were the models. We had no idea if the models were completely wrong." Computerized climate models vary widely in their predictions of how clouds will respond to long-term climate change. A few models predict clouds will be neutral players, neither compounding warming nor counteracting it, while others predict clouds will exacerbate warming. Some climate skeptics have alleged that models "got clouds completely wrong," Dessler said. He believes that his paper, which suggests long-term climate change will create a positive feedback from clouds that produces additional heating of the planet, "shows that models are doing a reasonable job as a group."

One of those skeptics is Roy Spencer, a climatologist at the University of Alabama, Huntsville. He issued a statement (pdf) yesterday attacking Dessler's study, calling its "central evidence weak at best, misleading at worst." Spencer has published a paper arguing that clouds will cool the planet and counteract warming. He drew on that work to argue that Dessler's study confuses the cause and effect of warming by failing to take into account the idea that changes in clouds drive temperature, rather than temperature changes driving cloud behavior.

Dennis Hartmann, a professor of atmospheric sciences at the University of Washington, agreed with Dessler. "I do think it's very significant that this analysis shows that a strongly negative, short-term cloud feedback is very unlikely, based upon the evidence, and that positive cloud feedback is more likely," said Hartmann, who did not contribute to the new study. "Current climate models vary widely on their assessments of cloud feedback. But if you were forced to draw consensus on what models are saying so far, they're saying that cloud feedback is moderately positive." The new analysis is based on the first 10 years of data collected by an instrument flying aboard NASA's Terra satellite that monitors how much radiation is entering and leaving Earth's atmosphere. The instrument, known as CERES (short for "Clouds and Earth's Radiant Energy System"), began collecting information in March 2000.

EDIT

http://www.nytimes.com/cwire/2010/12/10/10climatewire-n...

[Ezlivin]

1. It seems intuitive that cloud cover would trap and increase heat

Venus springs to mind.

It's just too bad that any uncertainty in the science of climatology is seen as a reason to do nothing. "We have to wait for additional data," as Bush was fond of saying.

[petronius]

5. Globally averaged, the net effect of clouds currently is a cooling

I.e., the surface is cooler than if there were no clouds at all. However, the local effect of cloud cover depends on cloud height, thickness, droplet size, time of day, etc - so a specific cloud may warm or cool the surface below it. The big problem with clouds in developing climate scenarios is not only figuring out whether future climates will have more or less cloud cover, but what type of cloud...

[Ezlivin]

6. Cirrus versus cumulus, eh?

Your explanation further expands upon and clarifies the effects of cloud cover.

The clouds prepare for battle
In the dark and brooding silence
Bruised and sullen stormclouds
Have the light of day obscured
Looming low and ominous
In twilight premature
Thunderheads are rumbling
In a distant overture

All at once,
The clouds are parted
Light streams down
In bright unbroken beams

Follow men's eyes
As they look to the skies
The shifting shafts of shining
Weave the fabric of their dreams...

Rush - "Jacob's Ladder"

[Nederland]

2. Here is a link to the Spencer paper mentioned

http://www.drroyspencer.com/wp-content/uploads/Spencer-...

Spencer basically claims that Dessler got it backwards: increased temperatures did not cause an increase in cloudiness--rather, increased cloudiness caused the increase in temperatures.

[joshcryer]

3. Dressler has already responded to Spencers blog:

http://www.realclimate.org/index.php/archives/2010/12/f... /

Just to follow this controversy, anyway.

[joshcryer]

4. "I’m in College Station this week, while Dr. Spencer is in Cancun"

Really drives home the conspiracy bullshit. Even "activists" like Gavin don't spend as much time arguing policy.

[Confusious]

7. If you lived in a cold area of the United States That's true.

Cloudy days would be warmer then clear days. The warmth would be caused by the clouds.

[pscot]

8. Ambiguity?

Maybe they're both right.