Climate change modeling: uncertainty due to cloud coverage?

Question

"There is a large uncertainty in the cloud feedback, but all current models predict that the feedback is positive." ( http://www.iop.org/activity/policy/Events/Seminars/file_25825.pdf )

Is this statement true? What would happen if the change in albedo due to cloud coverage is negative? What is the percent uncertainty in cloud albedo estimates from climate models?

Please provide links and specific numbers if possible.

Answer 1

Clouds and water vapor are quite possibly the largest uncertainty in the global climate models right now.  They're tricky because water vapor is a greenhouse gas and low elevation clouds trap heat below, but clouds also reflect sunlight and thus cause cooling.

It's a similar situation to the net effect of global warming on hurricanes.  You've got 2 combatting effects.  In the case of hurricanes, global warming increases sea surface temperatures (SSTs) and wind shear.  Higher SSTs means stronger hurricanes, but stonger wind shear means weaker hurricanes, so scientists are having a hard time figuring out what the net effect will be.

The general thought is that the net effect of increasing cloud cover will be one of warming.  Lindzen believes otherwise, which is basically the reason he's a skeptic, but the models disagree with him.

However, as you can see from the link below, the uncertainty of the radiative forcing from the cloud albedo effect is quite high.

Answer 2

They can not calculate it for the Texas area ..

Answer 3

en.wikipedia.org -

        Manda,

           Try this site - very informative

Answer 4

As your cite says, this is uncertain.  There are no specific numbers that are not highly speculative.

Clouds cut both ways.  Some (mostly high up) clouds cause cooling.  Lower clouds cause warming.  If we warm the air so it can hold more water vapor what will be the resulting increase of clouds of each type?

"In thermodynamics almost every feedback from an energy source is negative. In energy or power conservation the same holds true. This is due mainly to the fact a Cold body can not heat up a warmer body."

In global warming there are some obvious positive feedbacks.  Ice melts, exposes dark ground.  Warmer air holds more water vapor, increases greenhouse effect.  These things are not small.

Answer 5

What a great seminar that must have been!  That's the kind of debate that I believe keeps everyone on their toes and makes scientists go back and look again to make sure their data is as could as it could be.  I wonder about the role of the moderator on this one.  I hope he/she was more than just a timekeeper.

Saying the models are flawed is incorrect.  They are, however, imperfect, but improve as our understanding of the variables improves.

There are a number of uncertainties in relation to cloud feedback. But ultimately I believe there is enough good data in the mix to use the models as a tool in making decisions on how to mitigate gcc.

I'm not a scientist or a mathematician, so that's as far as I'm comfortable in going with this.  The models work overall.  In time they will perform even better.

Answer 6

That's been one of the major reasons that I've been skeptical of the whole movement all along.  That "large uncertainty" renders any predictions about as reliable as using a Magic 8 Ball to determine future trends.  Modeling things like cloud formation, ocean currents, air currents and the like are way beyond the capability of any current technology, yet the loyalists jump on any negative prediction based on these models as "factual" evidence of impending doom.

My position has always been that until we can actually ensure that the models are correct, we'd better learn to adapt to whatever might come down the road.

Answer 7

This is why I am skeptical.  In thermodynamics almost every feedback from an energy source is negative.  In energy or power conservation the same holds true.  This is due mainly to the fact a Cold body can not heat up a warmer body.  The major negative feedback which Lindzon mentioned was when CO2 absorbed energy it warms up, the it will then convect more heat to the upper atmospher and then into space and will cause more heat radiated into space by a Tn^4/Ti^4

Answer 8

a study the look at satellite data that came out last summer shows a negative, not positive feedback.

http://blog.acton.org/uploads/Spencer_07...

A NASA report says water vapour is less than what the models are forecasting:

Ken Minschwaner, a physicist at the New Mexico Institute of Mining and Technology, Socorro, N.M., and Andrew Dessler, a researcher with the University of Maryland, College Park, and NASA's Goddard Space Flight Center, Greenbelt, Md, did the study. It is in the March 15 issue of the American Meteorological Society's Journal of Climate. The researchers used data on water vapor in the upper troposphere (10-14 km or 6-9 miles altitude) from NASA's Upper Atmosphere Research Satellite (UARS).

Their work verified water vapor is increasing in the atmosphere as the surface warms. They found the increases in water vapor were not as high as many climate-forecasting computer models have assumed. "Our study confirms the existence of a positive water vapor feedback in the atmosphere, but it may be weaker than we expected," Minschwaner said.

http://www.nasa.gov/centers/goddard/news...

Answer 9

http://treestostay.blogspot.com/

Answer 10

see...textbook case for why they told us recess was just as important as studying!(you obviously still need to get out more!)

Answer 11

Good question... I think the jury is still out on this as the model is complex, computations huge and contributing factors not precisely known.

Personally I think the ephemeral nature of cloud cover is such that it won't play a large part in overall warming trends but may:

a) Exaggerate the chaotic phase (increased variability in, and extremes of, local weather conditions - hot one week, freezing the next)

b) Be a dampener at the extreme ends - if we enter a cooling phase may tend to keep things warm whereas if we are in a warming phase, to reflect more.

So a paradoxical influence: Moderating at the extremes of overall climate change while exaggerating the "mood-swings"

of mother nature locally.

But, hey! What do I know?

Sorry, but no sources I could find added much more than your link.

P.S. Thanks for the question; this is the sort of thing that I had hoped would be debated in this forum when I first joined not the quasi-religious divide that permeates...