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NASA Research on the Greenhouse Effect 34

Posted by michael
from the bring-the-marshmallows dept.
robsimmon writes "Since it's been a theme on Slashdot recently (with collapsing ice shelves and climate models) here's another article about global warming - scientists at NASA Ames have studied the one area on Earth with a runaway greenhouse effect (the Eastern Pacific). As the ocean gets warmer more water vapor enters the atmosphere, leading to more warming, etc. Unfortunately the press release doesn't say much about why the Earth doesn't continue to heat up, but does provide several possible explanations. Before the flame wars start again, you might also want to read brief NASA summary of global warming science. (a site I work on)"
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NASA Research on the Greenhouse Effect

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  • We have no money! Give us money!

    Then they go and spend several millions on "Perpetual computing" or some such crap. It looks like they've figured out a way to keep the politicians bent over with their asses hanging out and their wallets precariously perched.
  • Would you be able to call it a war with so few combatants?
  • [cnsnews.com]
    Global Warming Models Labeled 'Fairy Tale' By Team of Scientists
    By Marc Morano
    CNSNews.com Senior Staff Writer
    May 14, 2002

    Washington (CNSNews.com) - A team of international scientists Monday said climate models showing global warming are based on a "fairy tale" of computer projections. The scientists met on Capitol Hill to expose what they see as a dearth of scientific evidence about global warming.

    Hartwig Volz, a geophysicist with the RWE Research Lab in Germany questioned the merit of the climate projections coming from the United Nations sponsored Intergovernmental Panel on Climate Change (IPCC.) The IPCC climate projections have fueled worldwide support for the Kyoto Protocol, which aims to restrict the greenhouse gases thought to cause global warming.

    Volz noted that the IPCC does not even call the climate models "predictions" and instead refers to them as "projections" or "story lines." Volz said the projections might be more aptly termed "fairy tales."

    Monday's luncheon was sponsored by the Frontiers of Freedom Institute and titled "Whatever Happened to Global Warming? Climate Science Does Not Support the Kyoto Protocol."

    S. Fred Singer, an atmospheric physicist with the University of Virginia and the Environmental Policy Project, called the IPCC's global warming projections "completely unrealistic."

    ----------------

    You can read the rest yourself. I enjoyed it greatly I've often said exactly what these scientists are saying, and I get flamed for it. Bring on the flame-throwers, oh Chicken Littles!

    Bob-
    • The RWE [www.rwe.de] is (amongst other things) an electric and gas company. They mainly burn coal, natural gas and oil to produce electricity. Mr. Volz talking about global warming is like Mr. Burns talking about radioactive waste.
    • Looking at your sig you are obviously a man of right-wing persuasion.

      That is really a shame. Your politicians told you because the companies who pay to get them into office doesn't want to pay more to keep from polluting.... a shame in deed.

      I bet on cold days you also say things like: "This doen't feel like global warming" because you are some kind of armchair atmospheric physicist.

      If you are so afraid of loosing your SUV then you should demand higher gas mileage and do other things.

      You've been told that the Kyoto Protocol will take away our freedoms and maybe that is true. Sorry the USA isn't alone in the world. One day people around the world will all get sick of us at the same time and we will be in trouble.

      BTW, do you have insurance? On anything. Because if you do I think it's odd that you are against trying to insure that we won't destroy the planet.

      And on an end note:

      Silverman admitted there is room for some skepticism about global warming models because "nobody knows, we don't have god-like abilities [to predict the future.]"


      We don't. We can't just flip a switch in the future and reverse a trend if we start it.
  • "global warming may be the single largest threat to our planet. For decades human factories and cars have spewed billions of tons of greenhouse gases into the atmosphere" - EO [nasa.gov]

    Communists [monthlyreview.org]! All of them! These are the same kinda people who argue that the Earth is a globe, who pray to that demon Darwin, and who kill our unborn babies! Burn them!

    • although I appreciate the sarcasm, you could at least provide the quote in context. from the next paragraph:
      "On the other hand, there are those, some of whom are scientists, who believe that global warming will result in little more than warmer winters and increased plant growth."

      we do try to be fair.
  • Years ago I had the opportunity to talk to the scientist who coined the term "global warming".

    He sincerely regrets that moniker, and (correctly) blames much of the current obstructionism for the misunderstanding that the term has created.

    The real problem is that modification of the earth's albedo and atmospheric composition changes the way that energy from the sun is absorbed. If you can't understand that, go out in the parking lot on a sunny day and check out the difference in surface temperature on differently colored cars. Kapisch? If you put more carbon in the atmosphere, it absorbs more energy, and blocks some from directly reaching the ground. The differential between heat absorbed directly by the Earth's surface from solar irradiation and that absorbed indirectly from the atmosphere has been changed. If you strip out ozone from the upper atmosphere, you change the frequencies of light that are reaching the surface, with similar (but not entirely opposite) effects.

    If you are saying to yourself right now, "this is horseshit with no basis in reality" you can stop reading soon - God wants you to go up to the roof and jump off. Really, don't worry, your faith will take you directly to heaven. Honest, I'm a Republican preacher so you know you can trust me. Go do it now, Jesus is waiting for you!

    Now that we've weeded out the know-nothings and wishful thinkers, back to the subject: If you change the environment in this way, the easiest way to measure the progress of the changes (NOT the most accurate way, but the easiest way) is to look at global average temperature. This DOES NOT mean that your neighborhood gets warmer - in fact, your neighborhood may get significantly colder!! What this means is that the total energy absorbed by the Earth, rather than reflected, has increased. This gives us a crude measure of how rapidly we are fucking up the weather patterns by feeding more energy into an already chaotic system.

    So the next time some idiot (such as those already referenced above) tells you that "global warming isn't happening" you know they are morons with no understanding of the issue - or they wouldn't even use the term "global warming" as a basis for argument. If some other needledick tells you that "global warming isn't a problem, because we'll be able to grow more wheat in Canada and only the equatorial nations will get screwed" you'll know they are a bugfucker because global warming does not mean predictable increases in temperature in any specific area.

    One thing we can definitely expect: As we continue to modify our atmosphere, we will cause more violent weather due to more energy entering the system, and we will cause more species to go extinct as their operating parameters are exceeded. That's science and not wishful thinking by politically motivated pinheads.

    Flame away, Reaganistas!
    • The compositional change in the atmosphere (mostly how much CO2 is present) could theoretically be balanced by changes in the cloud balance (% of clouds to land area.) This would affect the albedo. I have seen research on this presenting solid evidence that the amount of cloudage has increased in the last few decades (the range of good global data.)

      Actually, I believe the biggest effect of global warming (at least a few degrees) is the rise in sea level due to ice cap melting, not single area warming or cooling.

      • You may be right, but I personally feel the biggest effect is the increase in species extinction rates. Reproductive problems in amphibians, particularly, can be attributed to changes in weather patterns.

        Of course, some scientists claim we were already well into the biggest extinction event since the Cretaceous before we even started the "Industrial Revolution".

      • The compositional change in the atmosphere (mostly how much CO2 is present) could theoretically be balanced by changes in the cloud balance (% of clouds to land area.) This would affect the albedo. I have seen research on this presenting solid evidence that the amount of cloudage has increased in the last few decades (the range of good global data.)

        You are absolutely correct - however, the changes in cloud cover could also increase global warming effect, depending on the cloud-top height. The albedo changes are important, of course, and cloud-cover is cloud-cover, as far as shortwave (solar) radiation is concerned, but the effect on global temperatures is based on the balance of the shortwave and the longwave (e.g. terrestrial longwave radiation.) And the type of cloud (low or high) changes the longwave effects.

        For example, low clouds, such as marine stratocumulus, radiate at approximately the same blackbody temperature as does the earth's surface, leading to no real net change in the surface IR budget of the planet, while reducing SW absorption by the surface (due to the increase in albedo, as you have correctly stated.) High clouds (such as cumulonimbus anvil cirrus) OTOH, radiate at a much, much colder IR temperature than do their low-altitude counterpart, and as such, contribute a net warming under the right circumstances to the net radiative budget. The type of cloud, composition, height, and thickness of the cloud all contribute to the cloud radiative forcing, and depending on the mix of these variables, can either negate global warming entirely, or enhance it in a runaway event. And the sad part is, we just don't know exactly which feedback mechanism is more likely.

        The fact that the globe has gotten cloudier (according to empirical evidence) is interesting in itself - but whether it's a good thing or not, we don't know yet. :)

        Actually, I believe the biggest effect of global warming (at least a few degrees) is the rise in sea level due to ice cap melting, not single area warming or cooling.

        Again, correct. I wish people would focus on this and not any assumed microclimate changes. :)
        • I wish I had mod points to mod the parent up.

          Most people don't know that we teeter on the edge of a venusian feedback cycle, with cloudcover contributing to the problem, not countering it.

          See also this graph extrapolating future CO2 concentrations with r^2>0.98 [bovik.org].

          • "Venusian feedback cycle" eh?

            Works great if you're on Venus, BOTOH Venus has the most circular orbit of any planet in the Solar System not an insignificant factor.

            More importantly Venus lies at a distance of 0.72 AU from the Sun. Thus with the inverse square law Venus receives approximately 1.3 times as much energy as the Earth, i.e. 30% more energy from the Sun as the Earth. This is VERY significantly in the runaway greenhouse effect on Venus.

            Trying to assert that any build up of greenhouse gases on Earth due to humanity will cause Earth to develop anything remotely like the atmospheric conditions on Venus in complete nonsense.
            • Works great if you're on Venus, BOTOH Venus has the most circular orbit of any planet in the Solar System not an insignificant factor.

              Hmm...IIRC, Earth's orbital eccentricity is only 0.0167 - pretty darn near circular. Besides which, orbital eccentricity plays essentially no role in determining mean characteristics - if it did, the Northern hemisphere winter would be warmer than Southern hemisphere winters, since Earth's perihelion falls during December. So I'm not sure what you're getting at.

              More importantly Venus lies at a distance of 0.72 AU from the Sun. Thus with the inverse square law Venus receives approximately 1.3 times as much energy as the Earth, i.e. 30% more energy from the Sun as the Earth. This is VERY significantly in the runaway greenhouse effect on Venus.

              You forgot to mention that Venus is smaller - it's mean radius is some 300km less than that of the Earth's. By my calculations, it therefore intercepts by area only 90% of what the Earth receives. Granted it's more 'dense' (per steradian) energy, but it almost balances out. Furthermore, the fact that Venus is entirely covered by clouds lead to a very high planetary albedo, which drastically reduces the amount of solar radiation the surface recieves. I remember calculating the Venusian effective surface temperature based on orbital characteristics as an undergrad - it came out to be pretty close to Earth's, IIRC. The dominant factor in Venus' hellishly hot temperature, therefore, is not due to its orbital characteristics, but rather its chemical composition.

              Trying to assert that any build up of greenhouse gases on Earth due to humanity will cause Earth to develop anything remotely like the atmospheric conditions on Venus in complete nonsense.

              Why do you say this? I doubt you could realistically support this argument. Were Earth to undergo a sufficiently strong positive cloud feedback, it would be entirely possible to achieve a runaway greenhouse effect. Where do you get your science from - your own calculations, or the TV?

              • "You forgot to mention that Venus is smaller - it's mean radius is some 300km less than that of the Earth's. By my calculations, it therefore intercepts by area only 90% of what the Earth receives."

                Correct.

                A(sphere) = 4pi r**2

                Ergo 1/2 A(sphere) would yield the surface area of a planet that would be exposed to solar radiation.
                Thus, given r(Earth) = 12750/2 km, and r(Venus) = 12100/2 km then the surface area of Venus exposed to solar radiation would indeed be ~90% of the surface area of Earth exposed to solar radiation.

                However, I made a typo on the calculator and got a solar flux density for Venus that was 30% of the solar flux density of Earth. This is incorrect. Venus actually has a solar flux density that is ~193% of that of Earth, i.e. nearly twice that of Earth.

                Using the inverse square law: flux density = 1/r**2, then given that Venus is a distance of 0.72 AU from the Sun then the solar flux density for Venus is:

                1/(0.72)**2 = 1/0.518 = 1.929 i.e. near twice that of Earth.

                To conclude:
                While Venus has an exposed surface area that is 0.9 times that of Earth, it receives a flux density 1.93 times that of Earth, thus as 1.93 * 0.9 = 1.74 then Venus receives ~ 3/4 more energy from the Sun than does the Earth.
                • While Venus has an exposed surface area that is 0.9 times that of Earth, it receives a flux density 1.93 times that of Earth, thus as 1.93 * 0.9 = 1.74 then Venus receives ~ 3/4 more energy from the Sun than does the Earth.

                  ...at top-of-atmosphere. You're still not accounting for the fact that the Venusian albedo is 0.65 - nearly twice that of the Earth (albedo = 0.37). Reflected solar energy does not contribute to the radiative balance of an atmosphere.

                  Just for old times' sake, I pulled out my calculations for surface effective temperature based on TOA incident radiation and albedo. Using NASA values for the Venusian TOA solar flux and albedo (see this [nasa.gov] link for the numbers - which confirm (as did my own calculations) that the incident solar flux at TOA of Venus is indeed 1.9 times that of the Earth) I compute using the standard equivalent blackbody temperature formula (e.g. Salby, eq. 1.30.2) that the effective temperature of Venus is 252 K (note that the NASA 'blackbody' temperature is not the effective blackbody temperature because we want to use the visual geometric albedo for shortwave calculations, not the bond value).

                  The equivalent blackbody temperature for Earth is ~255 K. Thus we see the importance of the greenhouse effect - not only does the chemical composition of Venus provide a ~500 K greenhouse warming, but the Earth undergoes an approximate 30 K warming itself, due to water vapor absorption and re-emission in the IR band. Therefore, anything that modifies the ambient surface water vapor budget (such as a slight warming due to CO2 increases, for example) will affect the Earth's 'natural' greenhouse effect. We would do well to understand this phenomenon completely before deciding that anthropogenic emission of CO2 plays no role in global warming. Regardless of all this, we see that the TOA solar fluxes are not the dominant term in the simple radiative budget, as the albedo contributes equally to the equation, and can trivially negate any solar 'advantage' that Venus would have over its more distant solar neighbors.

                  References: Salby, M.L., 1996: Fundamentals of Atmospheric Physics. Academic Press, 627 pp.
                  • Re:parent article correct (Score:1)
                    by Mr_Matt on Tuesday May 28, @02:16PM (#3596466)
                    (User #225037 Info)
                    ""While Venus has an exposed surface area that is 0.9 times that of Earth, it receives a flux density 1.93 times that of Earth, thus as 1.93 * 0.9 = 1.74 then Venus receives ~ 3/4 more energy from the Sun than does the Earth."
                    ...at top-of-atmosphere. You're still not accounting for the fact that the Venusian albedo is 0.65 - nearly twice that of the Earth (albedo = 0.37). Reflected solar energy does not contribute to the radiative balance of an atmosphere."

                    Let's look at your argument. You state that the Venusian albedo is near twice that of Earth, and thus makes a significant contribution to the greenhouse effect on Venus. Therefore, for the Earth to develop the sort of greenhouse effect that is present on Venus it would have to develop an albedo at greater than that of Venus, given Venusian TOA solar flux is ~3/4ths greater that the Terrestrial TOA solar flux.

                    Beyond that there is the question of atmospheric genesis. That Venus has an albedo ~twice that of Earth manifestly demonstrates divergent atmospheric evolutions. The differentiation in the magnitude of the solar flux at 0.72 vs. 1.00 AU in this divergence of atmospheric genesis is necessarily a first order factor. In the early solar system planetary bodies were very much hotter that they currently are. Ergo, the higher solar flux at 0.72 AU in ALL likelihood had a VERY significant impact on the chemical genesis of the Venusian atmosphere.

                    This leaves us with the real question here.

                    Can anthropogenic greenhouse gasses effect the chemical composition of the Terrestrial atmosphere to the degree that its composition reflects (;D) that of the Venusian atmosphere.

                    My answer to this question is that the potency of the differential in the solar flux between 0.72 AU, and 1.00 AU, combined with the residual heat of formation of planetary bodies in the early solar system differs by orders of magnitude from that of anthropogenic greenhouse gasses in effecting the chemical composition of the respective atmospheres of Earth, and Venus, and thus the respective albedos.
                    • Let?s look at your argument. You state that the Venusian albedo is near twice that of Earth, and thus makes a significant contribution to the greenhouse effect on Venus. Therefore, for the Earth to develop the sort of greenhouse effect that is present on Venus it would have to develop an albedo at greater than that of Venus, given Venusian TOA solar flux is ~3/4ths greater that the Terrestrial TOA solar flux.

                      No, no, no...my argument is that since the Venusian albedo is twice that of the Earth, the fact that Venus receives 1.9 times the solar energy of the Earth makes no difference for the effective surface temperature. Read my post again, and I apologize if that wasn't clear. What I'm stating is that the fact that Venus is at 0.72 AU has no effect on the surface temperature being warmer, as it stands presently.

                      Beyond that there is the question of atmospheric genesis. That Venus has an albedo ~twice that of Earth manifestly demonstrates divergent atmospheric evolutions. The differentiation in the magnitude of the solar flux at 0.72 vs. 1.00 AU in this divergence of atmospheric genesis is necessarily a first order factor. In the early solar system planetary bodies were very much hotter that they currently are. Ergo, the higher solar flux at 0.72 AU in ALL likelihood had a VERY significant impact on the chemical genesis of the Venusian atmosphere.

                      This is a more interesting point - it is possible (and realistically likely) that, early in the formation of the Venusian atmosphere, the additional solar radiation received by Venus allowed the precipitation of a runaway CO2 effect. All this shows, however, is that given a sufficient amount of greenhouse gas and solar radiation, a positive-feedback mechanism can occur. This 'runaway' effect will eventually stabilize as heavier and heavier atmospheric species are vaporized - on Venus, the runaway greenhouse stopped with the formation of clouds of SO2, which provide sufficient planetary albedo to stabilize the IR warming of the abundant CO2 present.

                      Finally:

                      This leaves us with the real question here.

                      Can anthropogenic greenhouse gasses effect the chemical composition of the Terrestrial atmosphere to the degree that its composition reflects (;D) that of the Venusian atmosphere.


                      I think the real real question here is this: can anthropogenic gases affect the chemical composition of the Terrestrial atmosphere to the degree that its radiative properties reflect that of the Venusian atmosphere.

                      Remember, the primary greenhouse gas on Earth is water vapor. The Venusian atmosphere is composed of some 82 bars of CO2. Earth contains a roughly similar mass of H2O, but we keep in it our oceans, not in our atmosphere. :) Both CO2 and H2O act to absorb and re-emit thermal infrared radiation - on Venus, the runaway greenhouse effect was virtually guaranteed since there's a phenomenal amount of the absorbing gas in the atmosphere. Here on Earth, we live in a more delicate balance: the surface temperature is not warm enough to vaporize more than a few tens of grams/kilogram of water vapor. This is regulated by the Clausius-Clapeyron equation, which relates the vapor pressure of water to (among other things) the temperature of the air. Thus the argument: an increase in the terrestrial surface temperature (for whatever reason) will coincide with a corresponding increase in water vapor. It is possible (although not well understood) that this can result in a positive feedback loop:
                      • Perturb the surface temperature upward
                      • This results in higher water vapor pressure due to increased surface evaporation
                      • Increase in water vapor leads to increased IR heating of surface
                      • goto 1


                      So there remain two key elements to understanding a 'runaway' greenhouse effect: One, what initial temperature perturbation is necessary to initiate a runaway feedback loop as described above. Two, what is the effect of increased water vapor on high cloud/low cloud cover? This will further modify the radiative properties of the atmosphere, through increases in albedo, and will either permit or negate a positive feedback reaction to occur. Naturally, the second point is one we fail to understand at present. :)

                      Regardless, is has been postulated that a sufficient increase in CO2 due to anthropogenic sources (perhaps as little as a few tens of ppmv more, say) would be sufficient to trigger a water vapor feedback event, or the famous 'runaway' greenhouse effect. We don't need Venusian quantities of CO2 for a runaway event: we only need enough to trigger a runaway event with the radiatively interactive chemical species we do have enough of, namely, water. And we do not sufficiently understand either point one or two well enough to know the answer to these questions.

                      Personally, I find the likelihood of a 'runaway' greenhouse event to be phenominally small, and the 'runaway' event to be largely unnecessary hype. What I do care about is the effect of even a slight warming - just a few degrees Celsius can have a dramatic impact on the climate. Regardless, it's not so much the orbital parameters as it is the chemical concentrations that determine the greenhouse effect, as I hope we've shown to the three people still reading this thread. :) Feel free to respond (post or email: see my homepage for the addy) if you have more to discuss, and I've enjoyed the replies!

          • Thanks for the compliment, but remember my main point: we don't know if we're teetering on the edge yet, because we don't understand the role clouds play. It's perfectly possible that an increase in global mean temperature will lead to an increase in high cloud cover, which tends to negate the greenhouse warming of CO2. The real problem is we don't know what's going to happen - we just don't understand the climate system well enough yet.

            Hampering the problem are posts like the guy that replied to your post - people who don't realize a cloud albedo feedback/radiative transfer budget topic, and instead post nonsense about anthropogenic gases. :) Thanks for the insightful reply - it's a shame people don't get karma for posting when they actually understand what the thread's about. :)
      • Genesis 1:4 "And G-d saw the light, that it was good: and G-d devided the light from the darkness"

        Actually, at one point here on Earth their was a time when you couldn't see out to the Sun.

        Sound fun?
    • I remember an interview with, I believe Carl Sagan. In reference to global warming he had a simple response.. somthing like "how conceited of humans to think we could possibly do anything lasting to this planet. The span of the human race is a blink of the eye for the planet. At least three times in the history of the earth, 99.9% of all life has been wiped out. Yet it bounced right back again.".

      So it boils(pun) down to our concerns about our species being able to survive. I think the fact that we are the only species capable of modifying our environment to survive in the most inhospitible conditions negates any real concern.

      But the real point may be how long we decide to scream about the sky falling when the likely scenario is that the equilibrium will shift in other ways and provide habitat possibilites elsewhere. Just as they have for the entire life of the planet.
      • So it boils(pun) down to our concerns about our species being able to survive. I think the fact that we are the only species capable of modifying our environment to survive in the most inhospitible conditions negates any real concern.

        You had better hope that you are right. I wouldn't want to be around during a mass die off to discover that we can't survive in the new environment.

        And shifting equilibriums can be quite bad. We evolved (both biologically, and socially) for a certain environment. If this environment shifts significantly, it might lead to a considerable decline in our quality of life.
    • Its the cow farts man, I tell you, its all the cow farts!

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