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What do we really need to know about clouds?

June 30th, 2006 by Sean Davis · 8 Comments

In many of my graduate classes, in many journal articles, and in any scientific assessment of the state of our knowldege about the climate system, statements like this one from the Intergovernmental Panel on Climate Change’s (IPCC) Third Assessment Report (TAR) summary can be found

Such (climate) models cannot yet simulate all aspects of climate … and there are particular uncertainties associated with clouds and their interaction with radiation and aerosols.

There is a recognition among atmospheric scientists (and of course, AGW contrarians!), that uncertainties in our understanding of clouds are problematic for everything from weather prediction to projections of future climate. In fact, the range of climate sensitivities of 1.5 – 4.5 °C quoted in the IPCC for a doubling of CO2 is largely a result of various representations of clouds in GCM‘s.

All of this begs the question, what do we need to know that we don’t already know about clouds?

This is a question I’ve been struggling with for the past couple of years. Almost every week I monitor the latest published works in a couple of different journals, and almost every week without fail there are several papers on some aspect of cloud physics. Needless to say, the amount of literature devoted to clouds is staggering, and even someone who studies this topic such as myself is quickly overwhelmed with the sheer amount of information out there. There is a bizarre dichotomy between the overwhelming body of work on clouds and the underwhelming ability to constrain the representation of clouds on a global scale. So why is this?!? Is it simply a matter of spatial resolution in GCM’s? An unsurprising difficulty in the attempt to represent physics over (at least) 10 orders of magnitude (~10-6-104 m)? A lack of data from satellite or ground-based remote sensing, or in-situ measurements? A lack of funding? A lack of scientific focus on the important “big picture” issues?

I suspect that to some degree the difference between a good scientist and a great scientist lies in the ability to identify these important big picture issues and steer their research in that direction. I hope that in the coming months and years, this blog will serve as a useful tool for both myself and other scientists to identify important research directions.

Tags: general interest

8 responses so far ↓

  • 1 sidd // Jul 11, 2006 at 7:07 pm

    I would like to know more about cloud physics. Could you
    recommend a text or web site that I might consult ?

    Clouds are fascinating from a condensed matter physics point of
    view, living as they do on the edge of a phase transition.
    Perhaps some ideas from self organized criticality might apply ?


  • 2 seand // Jul 13, 2006 at 9:49 am

    Hi Sidd,

    There are many sources of information on cloud physics. Here’s a couple that I’ve had more or less good experience with that I can think of (by no means exhaustive!), in no particular order:

    Radiation and Cloud Processes in the Atmosphere : Theory, Observation and Modeling — This is largely focused on radiative transfer within clouds, less so on cloud evolution/microphysics, as I recall.

    Fundamentals of Atmospheric Physics, by Murry Salby — Good intro to atmospheric physics, with some cloud basics in it (as I recall… don’t have it in front of me right now)

    IPCC TAR – Ch. 7 Physical Climate Processes and Feedbacks — This is a good overview of the role of clouds in climate.

    Cirrus, by David K. Lynch (Editor), Kenneth Sassen (Editor), David O’C. Starr (Editor), Graeme Stephens (Editor) — I’ve been reading this some lately. It goes into excruciating detail about cirrus clouds. Wouldn’t really reccomend it unless you want to know a lot of detail.

  • 3 roxy // Aug 5, 2006 at 5:19 pm

    what i was looking for was not on this wensite but it helped me out with some other questioneds

  • 4 Sibel // Aug 17, 2006 at 4:47 pm

    I would like to now what clouds are there for and what would happen if there wasn’t any clouds in the world?

    Also can you give me some godd websites to find this infomation im doin clouds for my assesment

    Thnakyou Sibel

  • 5 seand // Aug 17, 2006 at 5:04 pm

    Right now the Earth’s albedo, or reflectance, is about 0.3. This means that about 30% of the sun’s light is reflected back to space. If there were no clouds, the Earth’s albedo would be lower, and more sunlight would be absorbed. This would cause the Earth’s temperature to become warmer. A good description of what would happen if there were no clouds can be found here.

    According to them,

    If Earth was covered in ice like a giant snowball, its albedo would be about 0.84, meaning it would reflect most (84 percent) of the sunlight that hit it. On the other hand, if Earth was completely covered by a dark green forest canopy, its albedo would be about 0.14, meaning most of the sunlight would get absorbed and our world would be far warmer than it is today

    Good luck on your assessment.

  • 6 Sibel // Aug 21, 2006 at 10:44 pm

    Thankyou for helping me with this and ill talk to you guys later cyaz

  • 7 Sibel // Sep 20, 2006 at 5:03 pm

    hey can u give me a good website to tell me wat clouds mean? thanx

  • 8 nell // Sep 24, 2006 at 10:56 pm

    hello how r u? well i was wondering if u guys can give me some information on why clouds form shapes and how?

    also can u give me ur email adress so its easyer to contact u thanx (wen i mean contact i mean like ask u more questions thats if u do have an email adress?

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