Cloud 'feedback' affects global climate and warming, study says (w/ Video)

Dec 09, 2010
Image: NASA

(PhysOrg.com) -- Changes in clouds will amplify the warming of the planet due to human activities, according to a breakthrough study by a Texas A&M University researcher.

Andrew Dessler, a professor in the Department of Atmospheric Sciences, says that warming due to increases in greenhouse gases will cause to trap more heat, which will lead to additional warming. This process is known as the "cloud feedback" and is predicted to be responsible for a significant portion of the warming over the next century.

Dessler used measurements from the Clouds and the Earth's Radiant Energy System (CERES) instrument onboard NASA's Terra satellite to calculate the amount of energy trapped by clouds as the climate varied over the last decade. He also used meteorological analyses provided by NASA's Modern Era Retrospective-Analysis for Research and Applications (MERRA) and by the European Center for Medium-Range Weather Forecasts.

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"It's a vicious cycle – warmer temperatures mean clouds trap more heat, which in turn leads to even more warming," Dessler explains. His work is published in the Dec. 10 issue of Science magazine and is supported by a NASA research grant.

While climate models had long predicted that the cloud feedback would amplify warming from human activities, until recently it was impossible to test the models using observations.

"This work suggests that climate models are doing a pretty decent job simulating how clouds respond to changing climates," Dessler says.

Some prominent climate skeptics have recently been arguing that clouds would act to stabilize the climate, thereby preventing greenhouse gases from causing significant warming.

"Based on my results, I think the chances that clouds will save us from dramatic change are pretty low," he explains. "In fact, my work shows that clouds will likely be amplifying the warming from human activities.

"I think we can be pretty confident that temperatures will rise by several degrees Celsius over the next century if we continue our present trajectory of greenhouse gas emissions."

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GSwift7
1.9 / 5 (9) Dec 09, 2010
So he didn't get published in a peer reviewed journal? I wonder why not? Or, did they just forget to mention that part?

Hey, he's got a cool video for utube though. It looks professional. I wonder who he hired to make it?

Too bad those NASA instruments don't see at night or over rough terrain or at high latitudes.
interictal
5 / 5 (3) Dec 09, 2010
Doesn't say in the first paragraph the work is published in Science?
GSwift7
1 / 5 (1) Dec 09, 2010
Okay, lol, I though they were talking about the magazine and not the journal, because that's what it says. I looked on the web site and it's actually in the journal.

The actual journal abstract is a bit different than what this says here though.
GSwift7
2 / 5 (5) Dec 09, 2010
As a matter of fact, his data actually shows a possible range of feedback effects ranging from positive, as it says here, to negative, which he doesn't mention here.

This is still only daytime data. With the other half of the picture still missing, i'd be cautious about what the results really mean.

Here in South Carolina, we had one of the warmest summers on record this year, based daily 24 hour average temperatures, which is a fair way to measure it. Solely looking at daily high temperatures over that same time period paints an entirely different picture though. We never even got close to a daily record high on any single day of this year. It was unusually warm and cloudy nights that made the 24 hour average so warm. That's a good example of how only looking at half the data, as this guy is, can be extremely misleading. Once again, I don't think I would run right out and change my climate model just yet, if I had one.
ArtflDgr
1 / 5 (3) Dec 09, 2010
interesting that eiher all this stuf changed, or humans never existed... for if itdidnt change, then whae stoppepd it all from running off a cliff when things were higher, and us not being here.
BartV
not rated yet Dec 09, 2010
And what happens to all of the sun's energy that is radiated back into space by the clouds? I don't see that addressed here.
apex01
1.9 / 5 (9) Dec 09, 2010
Just more climate change propaganda.
PinkElephant
3.7 / 5 (3) Dec 09, 2010
To counter GSwift7's usual BS dump, here's the full transcript:
Estimates of Earth's climate sensitivity are uncertain, largely because of uncertainty in the long-term cloud feedback. I estimated the magnitude of the cloud feedback in response to short-term climate variations by analyzing the top-of-atmosphere radiation budget from March 2000 to February 2010. Over this period, the short-term cloud feedback had a magnitude of 0.54 ± 0.74 (2σ) watts per square meter per kelvin, meaning that it is likely positive. A small negative feedback is possible, but one large enough to cancel the climate’s positive feedbacks is not supported by these observations. Both long- and short-wave components of short-term cloud feedback are also likely positive. Calculations of short-term cloud feedback in climate models yield a similar feedback. I find no correlation in the models between the short- and long-term cloud feedbacks.


http://www.scienc...23.short
PinkElephant
4 / 5 (4) Dec 09, 2010
And oh by the way, CERES is not sensitive to night vs. day:
The Cloud's and the Earth's Radiant Energy System (CERES) is a 3-channel radiometer measuring reflected solar radiation in the 0.3-5 µm wavelength band, emitted terrestrial radiation in the 8-12 µm band, and total radiation from 0.3 µm to beyond 100 µm.


http://aqua.nasa....eres.php

Nor is it affected by "rough terrain". It's on an effin' satellite.

And oh last but not least, at night the effect of clouds is PURELY to enhance greenhouse effect: as there's obviously no sunlight to reflect back to space...
ryggesogn2
1 / 5 (6) Dec 09, 2010
Clouds are made of H2O.
eachus
1 / 5 (1) Dec 10, 2010
Over this period, the short-term cloud feedback had a magnitude of 0.54 ± 0.74 (2 sigma) watts per square meter per kelvin, meaning that it is likely positive.


There is a problem here, and it is why this particular issue is so effing hard to sort out. The error bounds larger than the result show one aspect of this, when I worked on 3d climate models, the problem was the effect of warmer air on cloud heights.

Everyone has seen a thunderstorm, or I hope you have taken the time to stand in a field, or seashore and watch the whole process. It is the ultimate in (mathematical) chaos. A very slight difference in initial conditions take you from nothing to a roaring monster. We couldn't get a small scale simulation to match reality until we added a lake. (Any sort of thermal plume source would do.)

Not enough room here to fit in all the caveats, but we couldn't extent that model to even widespread weather prediction at the time computers were not up to it.
eachus
3 / 5 (4) Dec 10, 2010
Over this period, the short-term cloud feedback had a magnitude of 0.54 ± 0.74 (2σ) watts per square meter per kelvin, meaning that it is likely positive.


I have no problems with this study, but I can add some background on why it is so effing hard to figure out whether the clouds are a positive or negative feedback system. My bet is on negative, due to the historical record.

But consider a thunderstorm. If you have ever watched a thunderstorm form and then break over you. You know how fast they can form and turn into huge whether systems. Thunderstorms also efficiently move heat higher in the atmosphere--after all they are just big heat engines.

Originally when trying to model thunderstorms on computers, they didn't form. Add in varied terrain or a heat plume from a chimney or lake, and boom it is there. One of the first early use of (mathematical) chaos theory was in modeling thunderstorms.

But modeling such storms today is still next to impossible.
Skeptic_Heretic
5 / 5 (1) Dec 10, 2010
Clouds are made of H2O.

And your commentary is made of Marjon, Jon the Hack Swenson, comments.
eachus
1 / 5 (1) Dec 10, 2010
Over this period, the short-term cloud feedback had a magnitude of 0.54 ± 0.74 (2σ) watts per square meter per kelvin, meaning that it is likely positive.


I have no problems with this study, but I can add some background on why it is so effing hard to figure out whether the clouds are a positive or negative feedback system. My bet is on negative, due to the historical record.

But consider a thunderstorm. If you have ever watched a thunderstorm form and then break over you. You know how fast they can form and turn into huge whether systems. Thunderstorms also efficiently move heat higher in the atmosphere--after all they are just big heat engines.

Originally when trying to model thunderstorms on computers, they didn't form. Add in varied terrain or a heat plume from a chimney or lake, and boom it is there. One of the first early use of (mathematical) chaos theory was in modeling thunderstorms.

But modeling such storms today is still next to impossible.
Skeptic_Heretic
not rated yet Dec 10, 2010
I have no problems with this study, but I can add some background on why it is so effing hard to figure out whether the clouds are a positive or negative feedback system. My bet is on negative, due to the historical record.

Observations say otherwise. The temp in the desert swings to freezing so quickly and easily because of the lack of water vapor and clouds insulating the heat from escaping to space.

The counter argument is on overcast days it is cooler because less visible light becomes black body re-radiation.

It doesn't have an exact measure for either. It's very regionally dependent.
GSwift7
1 / 5 (4) Dec 10, 2010
to counter Pink's usual BS dump:

0.54-0.74= -0.20

0.54+0.74 = +1.28

That's a range from -.2 to +1.28. As you accurately quoted from the original study abstract: "A small negative feedback is possible"

Next: Terra is in what's called a sun-synchronous orbit. It passes the equator at 10:30 am and pm. The CERES instrument is passive, requiring light from the sun to operate. All the CERES data are from 10:30 AM, which is the peak of the diurnal by the way. You don't get a full picture from using only CERES data. You have to combine it with active sensing data from Terra's Moderate-Resolution Imaging Spectroradiometer (MODIS) and lidar measurements of CALIPSO to get the full picture and obtain any nightime data. CERES doesn't even measure flux really. It measures radiance wich in anisotropic, so it needs to compare its results with other satellites to get a result I think?

I was mistaken about rough terrain, other satellites have trouble with mountains.
PinkElephant
5 / 5 (4) Dec 10, 2010
"A small negative feedback is possible"
But obviously unlikely, given the only way you can obtain it is by departing by almost 2 standard deviations from the measured value.
The CERES instrument is passive, requiring light from the sun to operate.
Wrong: "CERES products include both solar-reflected and Earth-emitted radiation from the top of the atmosphere to the Earth's surface."
http://ceres.larc.nasa.gov/
Terra is in what's called a sun-synchronous orbit...
A polar orbit with a period of 98 minutes. It spends just as much time over night-side, as it does over day-side.
You have to combine it with active sensing data from ... MODIS and ... CALIPSO
Only if you want to know cloud coverage in conjunction with radiative flux.
CERES doesn't even measure flux really. It measures radiance wich in anisotropic
Radiance correlates with flux, especially when averaged over many independent measurements.

Your "mistakes" are legion, but always in the same direction...
GSwift7
1.5 / 5 (2) Dec 10, 2010
Okay, disregard most of what I said above. It's been a long day and I was reading quickly rather than carefully.

The part about the results possibly indicating a negative feedback remains true though. If that negative result lies within his own stated error bounds, then that means the feedback could be negative. It doesn't matter how large his error bounds are. If it's inside the errror bounds, then you can't be certain it isn't a negative feedback. You can't just ignore the error bounds.
PinkElephant
5 / 5 (3) Dec 10, 2010
If it's inside the errror bounds, then you can't be certain it isn't a negative feedback.
You can't be certain, but you can bet on it. The odds are very good against it being negative: certainly better than 9:1.

If 2 sigma is 0.74, then 0.2 (for the "negative" outcome interval) represents 0.54 sigma. Assuming Gaussian PDF...

http://en.wikiped...ntervals

... then area under curve between +/- 1.46 sigma is erf( 1.46/sqrt(2) ) = erf( 1.03 ) = 0.855

(using this:)
http://www.daniel...c51.aspx

Of the remaining 14.5% of all samples, only 7.25% lie to the "negative" side of the mean. So, odds of the effect actually being negative, are 7.25%. (Put another way: odds it is positive, are 92.75%.)

But even if it were, against all odds, slightly negative, still as stated in the abstract quoted above, it wouldn't be nearly negative enough to make a dent in all the other positive climate feedbacks.
Shootist
1 / 5 (3) Dec 11, 2010
Here in South Carolina, we had one of the warmest summers on record this year, based daily 24 hour average temperatures, which is a fair way to measure it.


yada. And you still don't have a result which is accurate to within one degree C, while the Climate shysters and thieves want us to believe in a 1/10 of a degree accuracy of theirs.

And I continue to ask for a narrative undergraduate level defense of the averaging procedures use to generate an annual world temperature, but I don't think I will get one. The subject is just too complex, what with needing coefficients for radiative heating of water, average surface area of the oceans and effects of waves on such heating, absorption of re-radiated heat from the oceans partitioned into that due to Co2 and that due to water vapor -- just to mention a few such modeling factors.

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