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Model-data-comparison, Lesson 2

Filed under: — stefan @ 10 April 2008

In January, we presented Lesson 1 in model-data comparison: if you are comparing noisy data to a model trend, make sure you have enough data for them to show a statistically significant trend. This was in response to a graph by Roger Pielke Jr. presented in the New York Times Tierney Lab Blog that compared observations to IPCC projections over an 8-year period. We showed that this period is too short for a meaningful trend comparison.

This week, the story has taken a curious new twist. In a letter published in Nature Geoscience, Pielke presents such a comparison for a longer period, 1990-2007 (see Figure). Lesson 1 learned – 17 years is sufficient. In fact, the very first figure of last year’s IPCC report presents almost the same comparison (see second Figure).

Pielke’s comparison of temperature scenarios of the four IPCC reports with data

There is a crucial difference, though, and this brings us to Lesson 2. The IPCC has always published ranges of future scenarios, rather than a single one, to cover uncertainties both in future climate forcing and in climate response. This is reflected in the IPCC graph below, and likewise in the earlier comparison by Rahmstorf et al. 2007 in Science.

IPCC Figure 1.1 – comparison of temperature scenarios of three IPCC reports with data

Any meaningful validation of a model with data must account for this stated uncertainty. If a theoretical model predicts that the acceleration of gravity in a given location should be 9.84 +- 0.05 m/s2, then the observed value of g = 9.81 m/s2 would support this model. However, a model predicting g = 9.84+-0.01 would be falsified by the observation. The difference is all in the stated uncertainty. A model predicting g = 9.84, without any stated uncertainty, could neither be supported nor falsified by the observation, and the comparison would not be meaningful.

Pielke compares single scenarios of IPCC, without mentioning the uncertainty range. He describes the scenarios he selected as IPCC’s “best estimate for the realised emissions scenario”. However, even given a particular emission scenario, IPCC has always allowed for a wide uncertainty range. Likewise for sea level (not shown here), Pielke just shows a single line for each scenario, as if there wasn’t a large uncertainty in sea level projections. Over the short time scales considered, the model uncertainty is larger than the uncertainty coming from the choice of emission scenario; for sea level it completely dominates the uncertainty (see e.g. the graphs in our Science paper). A comparison just with the “best estimate” without uncertainty range is not useful for “forecast verification”, the stated goal of Pielke’s letter. This is Lesson 2.

In addition, it is unclear what Pielke means by “realised emissions scenario” for the first IPCC report, which included only greenhouse gases and not aerosols in the forcing. Is such a “greenhouse gas only” scenario one that has been “realised” in the real world, and thus can be compared to data? A scenario only illustrates the climatic effect of the specified forcing – this is why it is called a scenario, not a forecast. To be sure, the first IPCC report did talk about “prediction” – in many respects the first report was not nearly as sophisticated as the more recent ones, including in its terminology. But this is no excuse for Pielke, almost twenty years down the track, to talk about “forecast” and “prediction” when he is referring to scenarios. A scenario tells us something like: “emitting this much CO2 would cause that much warming by 2050″. If in the 2040s the Earth gets hit by a meteorite shower and dramatically cools, or if humanity has installed mirrors in space to prevent the warming, then the above scenario was not wrong (the calculations may have been perfectly accurate). It has merely become obsolete, and it cannot be verified or falsified by observed data, because the observed data have become dominated by other effects not included in the scenario. In the same way, a “greenhouse gas only” scenario cannot be verified by observed data, because the real climate system has evolved under both greenhouse gas and aerosol forcing.

Pielke concludes: “Once published, projections should not be forgotten but should be rigorously compared with evolving observations.” We fully agree with that, and IPCC last year presented a more convincing (though not perfect) comparison than Pielke.

To sum up the three main points of this post:

1. IPCC already showed a very similar comparison as Pielke does, but including uncertainty ranges.

2. If a model-data comparison is done, it has to account for the uncertainty ranges – both in the data (that was Lesson 1 re noisy data) and in the model (that’s Lesson 2).

3. One should not mix up a scenario with a forecast - I cannot easily compare a scenario for the effects of greenhouse gases alone with observed data, because I cannot easily isolate the effect of the greenhouse gases in these data, given that other forcings are also at play in the real world.


363 Responses to “Model-data-comparison, Lesson 2”

  1. 201
    stephen clarke says:

    Alright,first of all id like to say im not a scientist,meteorlogist,or any of the above.But i have questions that i would like to ask the professionals.I say professionals because its obvious that the views on this sight are clearly stated by top notch scientists and people who know what they are discussing.To begin with,I’ll start with the Co2 issue.Everyone says that the increase in Co2 is causing a a blanket in our atmosphere and trapping in the heat,is it safe to say that,that would be a true
    statement? Secondly,why is there so much argument about if we are really going through a large increase
    in our planet heating. The IPCC is the leading candidate for this hype but are their findings accurate?
    Is there true data and not computer models to verify this is happening on a global scale? Is it possible that erupting volcanoes could cause the rise in Co2 in our atmosphere? Now understandably,its been
    proven that HCFC’s and other types of chemicals is not good for the enviroment.But is it not safe to
    say,that increased Co2 levels is good for plant life and other types of vegatation? Now,considering that Water Vapor is 95% of greenhouse gases,would it not be safe to say that the increase in water vapor
    could be a cause of increased heating.Would the increase in water vapor trap in more heat? And lastly,
    what about the HOLE in the atmosphere.If a hole would exsist and would allow more radiation to enter,
    why would it not allow for things to escape it?I know that this a very complex subject and i thank you
    for listening to me.I’m also aware that sometimes there is no clearcut answer to certain questions,Im
    really concerned about the truths of this issue.Ive done quite a bit of research on this topic and
    seem to be getting alot of arguments on both sides by very compatent scientist.Is Global Warming really
    rapidly changing our planet because of fossil fuels or is something else happening that we are not being
    told about? thank you

    [Response: If you are genuinely concerned about these issues, please go to the material linked on the 'Start Here' page (at the top of this page). Much of your confusion will be clarified with a little background reading. - gavin]

  2. 202
    spilgard says:

    Re #195. This recalls an old argument put forward to disprove the theory of sound waves. On a quiet night, a cricket’s chirp can be heard from a mile away. If the ridiculous pressure-wave theory is correct, it means that this tiny insect is capable of keeping several cubic miles of air in a state of constant agitation. Nice try, silly scientists!

  3. 203
    tom watson says:

    So according to gavin, C02 contributes 20%. Well one wonders at the imagination of definition that comes up with 20%. And I do wonder at how the overlap works when there is at a minimum 20 times as much H20 as C02 by PPM. If the amounts of mass as I have described are correct and my specifications of specific heat and heats of fusion and vaporization is correct. I do wonder at what magic science give CO2 some green gas property that is orders of magnitude larger than it’s known physical properties.

    And then the objective observation of satellites shows no warming. All that CO2 with 20% magic warming green house gas property and it cannot be found.

    And rod taylor says amateurish. OK you cannot explain the magic of your science and anything that question the magic 20% must be amateurish.
    Rod I have read all kinds of crap and giberish all over realclimate.org.
    I am also a professional and I am give freely of my wisdom and time. And that article you call amateur, I find greatly informative and insightful. I did not scan it, I read it, I read again and I thought about it. It is a very rational application of deductive and inductive reasoning in how to simplify understanding the effects of doubling the amount of the trace gas CO2 in the Earth’s atmosphere. I believe scientists are not engineers because they think differently and vice versa. that is not good or bad, it’s different. All three of my children are engineers. We have conversations that no one other than engineers would have a clue about what we are talking about.
    Click on my name and you will find a small sample of my PASTWORK.

    If you cannot comprehend what is presented in that paper, if is is only amatuerish to you, well maybe climate science is the refuse of the amateur.

    It quite simple, If it has no heat it is cold. It has cooled, the heat was not trapped. the heat went away. All that which says it should have and it will have is wrong as it does not have.

    All all the expert who claim otherwise are in denial. Maybe my minds eyes can visualize the fluid mechanics of the atmosphere better or maybe not. But all forces, all properties, do not give CO2 any ability to be some 20% green house gas by any rational definition of the meaning of green house gas.

    Or maybe one can come up with some specific definition where it could be sane to say CO2 is the 20% gas. OK then the measurements show that green house gas effects compared with generic insulation effects and convection effects are 20 times smaller than currently modeled.

    [Response: Much as I find your desire to continually demonstrate your confusion, brave, even noble, its connection to the actual physical world is zero. Please go away and read something relevant - Kiehl and Trenberth 1997 would be a good start, and don't come back until you have a coherent argument as to why they, and everyone else, are wrong. Enough is enough. - gavin]

  4. 204
    Jeff says:

    Tom, it is hard to take you seriously when confuse simple processes such as absorption and adsorption. I can understand a misspelling here and there, but you have used this term seven times in your comments to this thread. Radiation cannot be adsorbed because a) it is not molecular and b) it does not form a thin film.

  5. 205
    Rod B says:

    Nick (180), the implication in “Humanity at large will not come around by itself until the stuff hits the fan in a way that is obvious without analysis…” is that you’re talking to the people in the context that ‘do you believe this and think we should do something about it’, is going to cause them a lot of grief and work. For instance asking “would you do this if Uncle Sam or his relatives gave you a whole lot of stuff?” is sure to get positive replies — even if the person has no idea what you’re asking about. It was also curious that far more people positively agreed with AGW than the number who had heard a lot about it.

    None-the-less, I was impressed with the thoroughness and openness of the poll. Hardly any pollsters publish the actual questions asked, to avoid being attacked for built-in bias (which far too many polls have). It did raise some thought questions in my mind. I think the hypothesis above is still valid. The somewhat surprising poll results remind me that any time one is dealing with mass psychology and predicting what the mass will do/support/resist is pretty much a crap shoot. I would hazard a guess that the preponderance of the pollees (??) who said they support AGW mitigation and have heard about GW still don’t have a clue of which they speak. But…, interesting.

  6. 206
    Rod B says:

    re Ike’s 182: a clarification: the US Navy does not have or take an official opinion on global warming; in fact there are mixed opinions within the meterology and oceanography branch, and within Naval Research. In any case they defer to NOAA and the Commerce Dept. for official pronouncements.

  7. 207
    Rod B says:

    ps not withstanding Gore’s declassifying naval measurements, which they view as military secret, for his own (and, granted, other scientist’s) use.

  8. 208
    Rod B says:

    No, Martin (185), I would and recently have challenged those mendacity examples here in RC. But, IMHO, it kinda ends with semantics, and I felt no benefit would accrue from re-running the debate

  9. 209
    Rod B says:

    David (198), do GW models predict jet stream shifts????

  10. 210
    David B. Benson says:

    Rod B (207) — I’m the wrong person to ask; I only reported what the article states.

    That said, I see know reason why a good general circulation model could not do so.

  11. 211
    JCH says:

    Are you claiming Al Gore, all on his little lonesome and without the approval of the Navy, declassified something the United States Navy wanted to remain classified?

  12. 212

    Re #207 where Rod B says do GW models predict jet stream shifts???

    That is what is says here!

    Cheers, Alastair.

  13. 213
    tom watson says:

    re 202 Jeff, well jeff, my typing sucks. And the only thing I check is when the spell checker in my firefox browser underlines a spelling or typo error. And to an EE, well db always goes together with 3. Currently jeff, firefox and EE are underlined. Jeff would not be. Firefox considers itself a proper name also. And EE well…. Maybe CO2 has some magical adsorption properties. It seems no observations find it’s 20% absorption of photons.

  14. 214
    Nick Gotts says:

    Re #203 Rod, certainly if you asked people “Will you give up flying / your car / eating meat / your plasma TV to stop climate change, even if people in other countries didn’t”, you’d surely get a different answer. However, this is the most comprehensive poll I’m aware of, it’s recent, and the order of the questions has been chosen carefully – for example the question about whether developing countries should cut their emissions came before the question which posed this as part of a deal whereby they got aid and technology, so we can see how much difference that made. I think there is a good chance that if political leaders, in the next few years, were to negotiate seriously for an international deal, people could be convinced to go along even with measures that would be economically painful, provided they were convinced the deal as a whole was more or less fair. At any rate, I think the poll shows that dismissing this possibility is too pessimistic.

  15. 215
    Jim Eager says:

    Re Stephen Clarke @ 199

    Everyone says that the increase in Co2 is causing a blanket in our atmosphere and trapping in the heat,is it safe to say that,that would be a true
    statement?

    A blanket is not a perfect analogy for the greenhouse effect, which is of course much more complicated. What CO2 and other greenhouse gases do is absorb heat energy in the form of infrared light radiated by Earth’s surface, blocking it from reaching space, much like a blanket would. But that energy doesn’t stay absorbed. Instead it is quickly released, either by being transmitted as sensible heat to other gas molecules through collision, or it is emitted right back into the atmosphere as infrared light, where it can be absorbed again, and emitted again, and so on. Eventually that energy does make it to space, but in the process it warms the atmosphere.

    Secondly,why is there so much argument about if we are really going through a large increase
    in our planet heating.

    Hardly anyone now asserts that there has been no warming since the actual measurements quite plainly show a clear and sustained warming trend over the past century, although some do still dispute the extent and cause of the warming. Recently the rate of warming has appeared to slow or stall, but it is not yet known if the this is because of year-to-year variation, or if the long term trend has actually changed.

    The IPCC is the leading candidate for this hype but are their findings accurate?

    Hype? The IPCC examined and summarised the current science on the state of the climate and the observed effects and potential effects of climate change. If anything, their summary is more conservative than many scientists. For example, last summer’s melt of Arctic sea ice outstripped the projections in the IPCC report. So has the rate at which the Greenland ice cap is melting.

    Is there true data and not computer models to verify this is happening on a global scale?

    Yes, mountains of it. Libraries full of it. Warehouses full of it. Walk-in freezers full of it. All of what is currently observed and measured about past and current climate change is from the real world, not computer model projections. What models are used for is analysing and understanding the real-world observations and measurements and making projections about the possible future extent and impact of climate change.

    Is it possible that erupting volcanoes could cause the rise in Co2 in our atmosphere?

    This one is a simple and clear-cut no. In modern times world-wide volcanic activity emits between 145 and 255 million metric tonnes of CO2 each year, depending on how many eruptions there are and how large they are, even in a year with a big eruption like Mt. Pinatubo in 1991. That is less that 1 percent as much as human activity emits each year, which is currently around 29 billion tonnes per year. The eruption of a megavolcano, such as the Yellowstone caldera, would be a different story, but in that case volcanic CO2 would be the least of your worries. In fact, if you live in North America you’d likely have no more worries at all.
    See: http://www.bgs.ac.uk/programmes/landres/segs/downloads/VolcanicContributions.pdf

    But is it not safe to say,that increased Co2 levels is good for plant life and other types of vegatation?

    It’s not as simple as that. Some plant species do thrive in CO2-rich conditions, all other conditions being equal, such as poison ivy and kudzu, but not all do, including many of our important cereal grains. Also, CO2 is only one plant nutrient, and plant growth is limited by the nutrient that is in shortest supply, not the one in most abundant supply. In any case, all other conditions will not likely be equal in a warmer, CO2-richer atmosphere. In a warmer world some agricultural areas will see less precipitation, or the rains will come at the wrong time in the growing season, so some crops may not be able to grow where they do now. Most of our crops are also sensitive to heat, again, including most of our grain crops, so they may not be able to grow where they do now even if water is available. As I said, it’s not as simple as CO2 is good for growing plants.

    Now,considering that Water Vapor is 95% of greenhouse gases,would it not be safe to say that the increase in water vapor
    could be a cause of increased heating.Would the increase in water vapor trap in more heat?

    It would, if the amount of water vapour in the atmosphere could be increased. But the amount of water vapour that the atmosphere can hold, or its relative humidity, is limited by temperature and pressure, so the only way to get more water vapour in the atmosphere is to first increase the temperature or the pressure of the atmosphere. You see the problem? Add more water vapour and it will just condense out and precipitate to the ground as rain or snow. This doesn’t happen with CO2, and we know it is accumulating in the atmosphere because we are emitting it faster than the ocean and biosphere can take it up.
    See: http://en.wikipedia.org/wiki/Humidity

    And lastly, what about the HOLE in the atmosphere.If a hole would exsist and would allow more radiation to enter,
    why would it not allow for things to escape it?

    I would think that it might since ozone is a greenhouse gas, and it might perhaps be a contributing reason why the Antarctic is so cold despite the prediction that it should be the poles that warm the most. Then again, the Antarctic ice cap is also very high, and therefore colder than the Arctic, and the continent is insulated from warmer air and water by circumpolar winds and currents, and the depth of the atmosphere at the poles is much less than elsewhere, so I don’t really know how much more radiant heat there is to lose due to the ozone hole. Maybe someone else can help with this question.

  16. 216
    Paul Middents says:

    Re Rod B #205

    The submarine Arctic ice data was very carefully sanitized to protect detailed submarine track and mission information. The operational side (submariners) were supportive of this effort. It happened because Mr. Gore pressed for it. The only opposition came from some within the intelligence community. This information was of great value to the Arctic research community. I’m not sure what you are trying to imply with the “for his own use” throw away line.

    I think there is a lot more submarine derived oceanographic data of great potential value that should be declassified and released to the scientific community.

  17. 217
    Rod B says:

    JCH, given Gore’s current status the Navy would have certainly had to agree to declassify the information. And though I’m sure their default preference would be to not declassify (always the case in DOD or any other) I’m sure they decided they could give up the measurements in the narrow strip of Arctic and ‘help science’ without losing very much military value. I have no idea if they fought hard against it or not. And I have no disagreement with it — though neither am I the one responsible to assure our subs can outmaneuver the Ruskies in the Arctic Ocean. My only point was to clarify that the Navy is not/was not publicly or officially jumping on the AGW cause.

  18. 218
    Rod B says:

    Alastair, Well, they didn’t actually say jet stream shifts are one of the outputs of GW models, though they surely try to leave that impression with phrases like “consistent with” and “these shifts fit the predictions..” I find it hard to believe that jet stream patterns are outputs of GW models, but would like to know if they are. Not a real important question; but seems it should be easy, simple and straightforward.?.?

  19. 219
    Rod B says:

    Nick (212), I still don’t go as far as your conclusions. But, as I said earlier, too, I was surprisingly impressed with the poll and its methodology, as you recite. There is a new little question mark in my brain’s garage.

  20. 220
    Rod B says:

    Paul (214), I appreciate the insight. “For his own use” was a well-deserved (IMO) cheap shot!

  21. 221
    Timothy Chase says:

    Jim Eager (#213) wrote:

    I would think that it might since ozone is a greenhouse gas, and it might perhaps be a contributing reason why the Antarctic is so cold despite the prediction that it should be the poles that warm the most. Then again, the Antarctic ice cap is also very high, and therefore colder than the Arctic, and the continent is insulated from warmer air and water by circumpolar winds and currents, and the depth of the atmosphere at the poles is much less than elsewhere, so I don’t really know how much more radiant heat there is to lose due to the ozone hole. Maybe someone else can help with this question.

    Ozone is a greenhouse gas. However, it operates primarily in the lower stratosphere. But this is not the main difference between it and other greenhouse gases. Ozone absorbs radiation principally in the UV band. As such it is able to absorb energy directly from sunlight. And thus if you increase the amount of ozone, in the lower stratosphere, you increase the warming in the stratosphere, and this will have the effect of reducing the warming that takes place at the surface — as some of that ultraviolet will be radiated back into space without ever reaching the surface. However, this isn’t something that receives a great deal of focus undoubtedly since the effects are minor.

    But in any case, ozone depletion is responsible for the majority of the cooling trend in the lower stratosphere. Given the fact that thermal radiation is radiated by the surface primarily in the infrared band and is quite negligible in the ultraviolet band, ozone depletion will have a negligible effect on the ability of the surface to radiate its thermal radiation.

    However, given the fact that it increases the temperature differential between the surface and the stratosphere, it increases the strength of the polar vortex and thus its cooling effect upon the surface — as is suggested by the cooling pattern around the south pole.

    For the image, please see:

    Antarctic Heating and Cooling Trends
    http://rst.gsfc.nasa.gov/Sect16/antarctic_temp-AVH1982-2004.jpg

    Other greenhouse gases are transparent to both ultraviolet radiation and visible radiation. They can neither absorb nor emit in those parts of the spectrum. As such, they rely upon the sunlight being absorbed by the surface and re-emitted as infrared thermal radiation for their effect as they are opaque to certain bands of infrared radiation.

    Methane operates primarily in the troposphere and carbon dioxide operates principally in the mid to upper troposphere — where the atmosphere becomes especially dry. Now as much of the infrared radiation that gets absorbed by greenhouse gases gets reradiated towards the surface, it will warm the surface. But more importantly, it lowers the rate at which radiation reaches the top of the atmosphere. Likewise, it lowers the rate at which thermal radiation reaches the middle and upper stratosphere — and thus the rise in tropospheric carbon dioxide is the dominant cause of a cooling trend found at those altitudes.

    In fact, this is what pictures such as the following rely upon for measuring concentrations of greenhouse gases at various altitudes:

    NASA AIRS Mid-Tropospheric (8km) Carbon Dioxide
    http://www-airs.jpl.nasa.gov/Products/CarbonDioxide/

    The image is carbon dioxide at 8 km. You will notice the plumes rising off the heavily populated east and west coast of the United States. What is being measured is the infrared radiation being absorbed and then reemitted by carbon dioxide. The thicker the carbon dioxide, the more opaque the atmosphere becomes to the infrared radiation in that channel. So in essence, you are seeing the enhanced greenhouse effect in action when you look at that photo. And we are able to do the same thing with water vapor and methane – a few of the videos found here deal with those:

    Multimedia Animations
    http://airs.jpl.nasa.gov/Multimedia/Animations/

    *

    Since solar radiation is relatively constant, this means that raising the level of greenhouse gases in the atmosphere results in an imbalance between the rate at which energy enters the climate system and the rate at which energy leaves the climate system. Since energy is conserved, the heat content of the climate system must rise — and it will continue to rise until the temperature is sufficiently high for the rate at which energy is emitted at the surface to compensate for the increased opacity of the atmosphere to thermal radiation — and for the rate at which energy enters the climate system to equal the rate at which energy leaves the climate system.

    *

    One small correction for Jim: while the absorption of thermal radiation by greenhouse gases will warm the atmosphere, the radiation of thermal radiation by greenhouse gases will cool the atmosphere, and as energy enters the atmosphere through moist air convection and thermals, this has the effect of shifting the balance between the warming due to the absorption of thermal radiation and cooling due to the radiating of thermal radiation in favor of cooling — such that the net direct effect of greenhouse gases is primarily that of cooling the atmosphere while warming the surface. However, this isn’t uniformly the case throughout the atmosphere — as carbon dioxide (for example) will result in net direct warming of the atmosphere over a certain range of wavelengths over a certain range of atmospheric pressure.

    The following shows calculated degrees of cooling per day*wavelength as a function of pressure (which decreases exponentially with altitude) and wavelength for co2, ozone and water vapor.

    Radiation & Climate: Major Projects
    Line-by-line calculation of atmospheric fluxes and cooling rates 2
    http://www.aer.com/scienceResearch/rc/m-proj/abstracts/rc.clrt2.html

  22. 222

    Re #216

    Rod,

    I don’t think that the models output the latitude of the jet stream, but they do produce a simulation of the global climate in action which would have jet streams in it. By the Law of Averages some of the models will have the jet stream moving polewards :-)

    I went to a conference at the Royal Society a few weeks ago and tried to convince an expert there that I had found out where the models were going wrong. I was told that it was impossible that I was correct because the professor had 30 years experience with climate models. Moerover, if looked at the output from the models I would see their outputs were exactly the same as seen in the satellite photographs. But… In the next session of the meeting it was stated that the models produce a double Intertropical Convergence zone (ITCZ.)

    Isn’t that true Gavin? You were there.

    For those who do not know, the ITCZ is the main (single) cloud formation that wraps around the equator in the tropics produced by the meeting of the Hadley Cells, and can be seen on satellite images such as this this one or this one. One wonders, if the modellers cannot get that right how much reliance to place on their predictions for the jet stream. One also wonders how an expert with 30 years experience in climate modeling did not know that one and one makes two!

    Cheers, Alastair.

  23. 223

    Martin Lewitt writes:

    You may have missed the discussion of the Camp and Tung results in this thread:

    No, I didn’t. I became suspicious of their results when I realized they weren’t accounting for the Earth’s albedo when they made their preliminary flux calculations, which introduces a 31% error right there. If their approach is that sloppy, they probably made plenty of other mistakes as well.

    [Response: I would recommend a more wait and see attitude, KK Tung has a very good track record and so I am doubtful about your claim. I'll try and have a look at it when I get some time. - gavin]

  24. 224

    tom watson writes:

    Dear Barton Paul Levenson, do have such an instrument? How does it work and what does it tell you about how CO2 is causing back radiation?

    No, my climatology is all on the theoretical side. To attribute the back-radiation to CO2, I assume they checked which wavelengths the energy was coming in on. The wavelengths at which CO2 absorbs infrared energy are the same wavelengths at which it emits infrared energy, e.g. the very strong bands around 14.99 microns.

  25. 225

    tom watson writes:

    H20 has concentrations of 20 to thousands of times that of CO2.

    Water vapor averages about 3870 ppmv and carbon dioxide about 385 ppmv, so it’s about ten to one. It’s less than that by mass, since the carbon dioxide molecule weighs twice as much as a molecule of water vapor (44 AMU versus 18).

    H20 adsorbs serveral times the wavelenghts of CO2 if in equal concentrations with CO2.

    Don’t you mean “absorbs?” Adsorption refers to stuff collecting on a grain, I believe, like glass beads cooling off and adsorbing water. I could be wrong but that was the impression I had.

    It’s specific heat is similar, but H20 has a heat of fusion plus vaporization that is 600 times that of CO2.

    The latent heat of vaporization of carbon dioxide is about 571,300 Joules per kilogram, compared to 2,260,000 for water vapor — about four times as high, not 600 times as high. And since carbon dioxide is almost always a gas at Earth climate temperatures, its latent heat doesn’t really affect anything. Water vapor is the major substance with a phase-change cycle in the Earth system.

    There is more H20 than CO2 by orders of magnitude.

    See above.

    It’s heat storage is a few orders of magnitude greater than CO2.

    The heat capacity or specific heat of water vapor is around 1870 J/K/kg, compared to 850 or so for carbon dioxide — about three to one.

    And H20 adsorbs an order of magnitude of more wavelengths than CO2.

    Again, I think you probably mean “absorbs” here.

  26. 226

    JCH writes:

    Are you claiming Al Gore, all on his little lonesome and without the approval of the Navy, declassified something the United States Navy wanted to remain classified?

    As Vice President, Al Gore managed to get the information on thinning Arctic ice declassified, yes.

  27. 227

    Gavin writes (understandably):

    Response: I would recommend a more wait and see attitude, KK Tung has a very good track record and so I am doubtful about your claim. I’ll try and have a look at it when I get some time. – gavin

    I don’t mean to slander a colleague, and you’re right that they might be vindicated. But reading the preprint at

    http://www.amath.washington.edu/research/articles/Tung/journals/solar-jgr.pdf

    I find the text in the introduction (not the abstract, my bad):

    The factor of 4 is to account for the difference between a unit area on the spherical earth and the circular disk on which the solar constant is measured, while 0.85 is to account for the 15% of the TSI variability that lies in the UV wavelength and is absorbed by ozone in the stratosphere with the remaining reaching the lower troposphere, the surface and the upper ocean [Lean, et al., 2005; White, et al., 1997].

    Note that they’re talking about surface warming, which is the only reason I can figure out for why they’d ignore heating of the atmosphere. And I don’t see the albedo mentioned anywhere in there, or in the text surrounding it. It looks awfully like they just forgot about it.

    Plus, the amount of UV absorbed should be about 7%, shouldn’t it? Rather than 15%? All the solar energy absorbed in the atmosphere is only 19-20% of incoming according to K&T ’97, so it’s hard to believe that most of that is ultraviolet.

  28. 228
    Jim Eager says:

    Timothy, thanks for addressing the role of ozone and it’s south polar hole, and for expanding on the greenhouse mechanism. I was trying to give Stephen a explanation that was better than the simple blanket analogy without getting too technical, but I oversimplified. And in my haste I somehow got ozone mixed up. I do know that it is excited by UV, not IR. Shouldn’t post late in the evening.
    Regards,

  29. 229
    Jim Galasyn says:

    Those sunspots/cosmic rays/phlogiston particles are certainly working their magic:

    March the warmest on record over world land surfaces
    By RANDOLPH E. SCHMID, AP Science Writer
    Thursday, April 17, 2008

    (04-17) 17:41 PDT WASHINGTON (AP) — Planet Earth continues to run a fever. Last month was the warmest March on record over land surfaces of the world and the second warmest overall worldwide. For the United States, however, it was just an average March, the National Oceanic and Atmospheric Administration reported Thursday.

    NOAA’s National Climatic Data Center said high temperatures over much of Asia pulled the worldwide land temperature up to an average of 40.8 degrees Fahrenheit (4.9 degrees Celsius), 3.2 degrees (1.8 C) warmer than the average in the 20th century.

    While Asia had its greatest January snow cover this year, warm March readings caused a rapid melt and March snow cover on the continent was a record low.

    Global ocean temperatures were the 13th warmest on record, with a weakening of the La Nina conditions that cool the tropical Pacific Ocean.

    Overall land and sea surface temperatures for the world were second highest in 129 years of record keeping, trailing only 2002, the agency said.

    Complete analysis: NCDC: Climate of 2008

  30. 230
    tom watson says:

    Dear Barton Paul Levenson re 223: I expressed the numbers in what I feel are the most reasonable based upon what exists.

    Now 20 to thousands, my ratio of water to H20 can actually be 1 to thousands. But 1 to 30 covers only the vapor phase of H20 and 5 to 20 covers what I guess to be the majority, And in the tropics, 15 to 25 would be most common.

    In comparing heat of fusion, specific heat and heat of vaporization I count none fof CO2 as on Earth in the range of normal Earth temperatures and pressures CO2 does not undergo any phase change. Ingornance of such considerations may be considered a far greater ignorance than the possible mistaken use of adsorb.

    Now specific heats are .85 and 1 for C02 and H20, molar weight is 40 and 18.
    molecule specific heat is thus 1.888. We can say twice. But heat of fussion and heat of vaporization are added. They are 0 and 600.

    So even using your twice with your 10 times as many. you muliply 5 by 600. which gives 3000. In the tropics where solar energy is double and quadruple that of higher latitudes, where the heat of advective warming come from, the effects of water do reach impacts of thousands over that of CO2.

    I have more detailed explanations of CO2 and H20 at http://toms.homeip.net/global_warming/what-the-hell-is-air.html

    And last night I added a new annotated dew-point-PPM-Relative_Humidity.jpg
    http://toms.homeip.net/global_warming/dew-point-PPM-Relative_Humidity.jpg

    And forgive me Barton Paul Levenson, I find unless one seeds some glaring error or exaggeration, one gets a less serious consideration. It is funny how human nature is that way.

    So Barton Paul Levenson, do you know where one finds the explanation, the math and the hand waving that shows how CO2 is the 20% green house gas as pontificated by “the gavin” who has the power of the green text.

    [Response: I told you to read Kiehl and Trenberth, then try Clough and Iaconno (1995), or Ramanathan and Coakley (1979), or even read my post on the topic -it's not perfect, but it's close enough. None of this has anything to do with specific or latent heats. - the gavin]

  31. 231
    tom watson says:

    Re Jim Eager 213: That was a very good post. I personally do not like every using the term blocking, I think consistently in terms of delay. If every fall there is a new frost on some day here in Monroe CT. The delay of the hear of summer is ended. Other than that it was every good.

    You also said:
    Hardly anyone now asserts that there has been no warming since the actual measurements quite plainly show a clear and sustained warming trend over the past century, although some do still dispute the extent and cause of the warming. Recently the rate of warming has appeared to slow or stall, but it is not yet known if the this is because of year-to-year variation, or if the long term trend has actually changed.

    If heat is delayed, a day, a month, a year, a decade, that heat must be somewhere. When there is a globally cold year, has not all heat stored from the past been dissipated. If it has not, where is it?

    A warmer year only suggests there has been heating, It is a sum of integration of all past non dissipated heat and pressent heating. A colder year shows that nothing has delayed the dissipation of the past heat.

    All I’ve read says the ocean is not warmer and the atmosphere is not warmer.
    Yet CO2 has had it 20% supposed green house gas effect (according to the gavin) augmented by how much in the last 5, 10, 20 years.

  32. 232
    Ike Solem says:

    Well, it’s pretty clear that the models underestimated the rate at which Arctic ice is melting – apparently due to oceanic heat transport and dynamic mixing in the atmosphere. RodB says that this is not the “official position” of the Navy.

    However, that’s not quite true: Now the Pentagon tells Bush: climate change will destroy us, 2004

    The document predicts that abrupt climate change could bring the planet to the edge of anarchy as countries develop a nuclear threat to defend and secure dwindling food, water and energy supplies. The threat to global stability vastly eclipses that of terrorism, say the few experts privy to its contents.

    Many scientists have looked at the issue of why the Arctic is melting so fast, and this comment from the interview is worth looking at to understand how interdisciplinary climate science works:

    Dr Wieslaw Maslowski: Well, personally I have my own perspective on all the carbon emission and global warming. However, I wanted to make very clear that the tools that we have used so far for our studies are not involving or allowing us to discriminate between greenhouse gases effect or other climate variability. So, what we see is what we see but there is no direct cause, there is no possibility for us to link direct cause of ice melt to something like greenhouse gases. My personal perspective is that we definitely should be cutting on the emission rates worldwide and it may not stop whatever the changes that are happening right now but we are still not very certain what kind of changes we can expect not only within the next 10 years but within 20 – 50 years into the future. So, if we sit and do nothing then definitely it will be much worse than if we try to actually reduce our pollution and emissions of carbon dioxide into the atmosphere for the long term.

    Other scientists have looked closely at at the possible forcings for climate, however – carbon dioxide emissions, methane emissions, N2O emissions, the water vapor feedback (which links to precipitation and cloudiness changes, indirectly), changes in solar irradiance, reflective aerosols in the atmosphere, black carbon aerosols over snow, changes in land and ocean albedo, and so on – so we can use that work to show that fossil fuel combustion is the main cause of the observed warming.

    Take solar forcing. Some claim that the present warming is due to “early 20th century increases in solar intensity” by referencing fig 4 in Lockwood & Frohlich (2007) (Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature.)

    Well, we know that changes in solar intensity have a response time of a few years, not five decades, because when Pinatubo injected all those aerosols into the atmosphere, the reflection of sunlight led to a cooling and drying of the global atmosphere within a few years. Increases in solar radiation don’t require a fifty-year lag time to see a response. So, if solar irradiance has been flat and even slightly decreasing recently, there is no way that could be the main factor.

    On the other hand, people who look at atmospheric CO2 and methane all agree that these gases are warming the planet based on complicated physical calculations and detailed observations of the present and of ice cores, very well discussed here at RC. What people don’t have a good understanding of is how fast this will happen – but when models predict a ice-free Arctic in 2100, and observations indicate an ice free Arctic in a decade or so. . .

    It makes you wonder if we are also going to soon hear that “models have underestimated the rate of warming and melting around Antarctica.”

  33. 233
    JCH says:

    I think it was actually Bush and Gates who declassified the Arctic information for Senator Ozone Man. Not the current versions of Bush and Gates, but the old versions of Bush and Gates.

    [Response: Nope. It was Gore. - gavin]

  34. 234
    David B. Benson says:

    Barton Paul Levenson (223) — I agree. He should have written ‘absorbs’ and your understanding of ‘adsorbtion’ is essentially correct.

  35. 235
    JCH says:

    “The push for scientific access to this secretive realm began some two years ago in Congress, with Senator Al Gore gaining a preliminary release of data. Momentum built slowly in private groups like the Council on Foreign Relations and recently gathered speed in the Bush Administration as criticism of its environmental record mounted.

    On May 28, President Bush, a former Director of Central Intelligence with a special interest in spy satellites, signed a directive that cleared the way for environmentalists to use the nation’s spy gear and records. Already, three teams of scientists and intelligence officials are being formed to explore this new frontier. …” – NYT, 1992

  36. 236
    Phil. Felton says:

    Re #228

    Given your misunderstanding of the mechanism of GHG you might try reading:

    Chemistry of Atmospheres: An Introduction to the Chemistry of the Atmospheres of Earth, the Planets and Their Satellites
    By Richard P. Wayne

  37. 237
    Ike Solem says:

    JCH, that refers to the use of satellites to get data on things like the extent of deforestation in the Amazon and Indonesia, the rate of desertification in Africa’s sub-Saharan Sahel, and so on, as reported in the Wall Street Journal. Any scientist who wants access to that data has to go through a fairly extensive background check in a very controlled process, and that’s why we now have good estimates of Arctic sea ice extent. Obviously, who gets to use look at such satellite information is a sensitive matter.

    Until now, only a handful of federal civilian agencies, such as the National Aeronautics and Space Administration and the U.S. Geological Survey, have had access to the most basic spy-satellite imagery, and only for the purpose of scientific and environmental study.

    What these records are, however, are nuclear submarine records for a limited region of the planet, the Arctic, beginning when nuclear submarines first began taking long voyages under the Arctic ice, beginning in 1958, during which temperature and ice thickness data were taken.

    There are many still-classified records of submarine voyages that would likely give a far better picture of the history of global ocean temperatures over the past fifty years or so. It is possible that if all that data was released, it would show what submarines had been where when, but it is of course possible to filter the data to hide all that information, somewhat reducing the accuracy maybe, but still better than no release of data at all.

    The first paper written using the submarine records was

    Thinning of the Arctic Sea-Ice Cover
    D.A. Rothrock, Y. Yu, and G.A. Maykut
    University of Washington, Seattle, Washington
    GEOPHYSICAL RESEARCH LETTERS, VOL. 26, NO. 23, PAGES 3469-3472, DECEMBER 1, 1999

    Comparison of sea-ice draft data acquired on submarine cruises between 1993 and 1997 with similar data acquired between 1958 and 1976 indicates that the mean ice draft at the end of the melt season has decreased by about 1.3 m in most of the deep water portion of the Arctic Ocean, from 3.1 m in 1958 – 1976 to 1.8 m in the 1990s. The decrease is greater in the central and eastern Arctic than in the Beaufort and Chukchi seas. Preliminary evidence is that the ice cover has continued to become thinner in some regions during the 1990s.

  38. 238
    tom watson says:

    Dear “the gavin” re: [Response: I told you to read Kiehl and Trenberth, then try Clough and Iaconno (1995), or Ramanathan and Coakley (1979), or even read my post on the topic -it’s not perfect, but it’s close enough. None of this has anything to do with specific or latent heats. - the gavin]

    I expect Clough and Iaconno or Ramanathan and Coakley would only say what is written in your fine post. 2005/04/water-vapour-feedback-or-forcing/
    I do appreciate your link. feedback or forcing, I don’t comprehend in that description or over-simplification. I do not argue your description is wrong, but very incomplete.
    Do I have the skills to express with words what is clear in my minds eye?

    Where do I, how do I construct the common reference of understanding.
    What you speak about may be true for the conditions at zero altitude. But as one goes higher into the altitude, the blocking of CO2 and H20 to heat returning to the earth gets greater and greater over that free path of escape to space.

    As you point out, H20 fills any vacuum, any sub dew point atmosphere very quickly. That H20 is also a convection forcing agent. Convection I see as short circuiting the ability of all parts of the atmosphere to delay the eventual escape of heat to space. And the convective short circuits increase as one approaches lower altitude to the ground.

    The temperature of the earth is
    1. the Current imput of the Sun
    2. plus the heat delayed by GHG
    4. plus the heat delayed longer stored in oceans.
    5. plus other??? (to cover but you did not mention and I skipped 3)
    minus the heat escaping via radiation.

    CO2 doom advocates see CO2 increasing 2 and 3, and 2 effects increasing 4.
    I believe, my life wisdom sees h20 driven convection makes all the suppositions on CO2 doom scenario extremely unlikely.

    All current measurements cannot find the required delayed heat from the supposed CO2 GHG properties. There is always the ivory tower of suppose and the real world of what satellites see. Satellite vision over the last couple of decades does reveal truths with implications that confirm and deny ivory tower suppositions.

  39. 239
    aaron says:

    I’m curious, following Pinatubo how much did humidity fall, how much did percipitation change, and how much did evaporation decrease, and how much water remained in the air as increased clouds?

    Anyone know of some good reading?

    Also, how can I figure out how much a lack of sunlight would change humidity, keeping temp equal, for various temps?

  40. 240
    JG says:

    It’s interesting to watch the “he did / no she did” comments about the declassification of data for environmental purposes. As one who participated in some aspects of the pre-ETF events, I can tell you that Bush/Clinton/Gore/Bush/”whichever politician you want” was just the visible link in a long chain of scientists who, with feet in both worlds, pushed hard for the use of remarkable synoptic data sets with, at the time, remarkable technical quality. As I commented to one of my (planetary scientist) colleagues in early 1992, the period of arm-chair geological field trips (of Earth) was about to start (this was pre-Google Earth which is much better!). But, the declassification process is a long one spanning many years. So whether Senator Gore encouraged it (as a spokesman for the scientists who knew what they wanted and why), President Bush who authorized it through the EFT and other acts, or President Clinton signed off on specific data sets, none was the scientific driving force. Of all of these politcos Senator (and VP) Gore best understood the implications of these data sets and became a vocal advocate. But that matters little. The role of the President in signing or authorizing declassification into law or action is deciding how best to protect the vital interests of the US, a decision based on the collective wisdom of advisors and the President. So, what difference does it make who claims “first” in this issue? Just be glad there were scientists in the know, political advocates with a smidgeon of understanding and Presidents who wisely listened to advisors. It could have turned out different.

    For reference, so we can include President Clinton in the fray: http://www.nro.gov/PressReleases/prs_rel.html . There are many more documents of historical interest that explain the real background of it all – it is never what it seems – but unlikely to be published anywhere.

    Great blog site. Brave and patient souls on all sides of the issue. Keep posting!

  41. 241
    JCH says:

    Actually, the New York Times article referred specifically to various measurements taken by vessels of the United States Navy, and that included measurements of the thickness of Arctic ice.

  42. 242
    Timothy Chase says:

    Jim Eager (#228) wrote:

    Timothy, thanks for addressing the role of ozone and it’s south polar hole, and for expanding on the greenhouse mechanism. I was trying to give Stephen a explanation that was better than the simple blanket analogy without getting too technical, but I oversimplified. And in my haste I somehow got ozone mixed up. I do know that it is excited by UV, not IR. Shouldn’t post late in the evening.

    Honestly I thought you had done a good job and was somewhat envious of the patience you were showing the person you were responding to. But then I saw a point or two I thought I could touch on but was rushed enough that my ability to hit just the points that needed it was pretty much shot, so what you got was almost stream-of-consciousness. I had to get up in six hours, have been dealing with a heck of a commute and not getting enough sleep — and weekends have been downtime — to the extent that they weren’t swallowed up by work. My apologies.

  43. 243
    Rod B says:

    This discourse over my minor clarification is curious. Fortunately it’s being taken over by the “he did; no, she did” (JG), which also matters not a twit in the scheme of things as JG points out. But, to keep Ike (232) et al on tract, the US Navy takes no official position, pro or con, on AGW. Would they admit (if they had to) that Arctic ice is melting due to “oceanic heat transport and dynamic mixing in the atmosphere” the answer has to be yes: what the hell else is there? Secondly, DOD is taking no official position on the prediction for or against AGW — the editorial license taken by the Observer not withstanding. Are they contemplating the effects, threats, and possible responses if it occurs? I certainly hope so! Just because they have invasion plans for nearly every place on earth (and they do, at some level or another) doesn’t mean they predict or expect their use.

  44. 244

    tom watson –

    The figures for relative contribution to the greenhouse effect come from radiative-convective models of Earth’s atmosphere, and removing the components one by one to see what the effect is. This model, which gets quoted a lot, finds that 26% of the clear-sky greenhouse effect is accounted for by carbon dioxide:

    K&T97

  45. 245
    John Finn says:

    Re: #190

    Martin Lewitt writes:

    The Sun has gotten hotter. The fact that it did so prior to 1940, and then just pretty much just remained so, does not alter its ability to explain warming, even to this day .

    BPL responds : Yes it does.

    OK, BPL, assuming all other factors had remained the same, when do you think the warming from the increase in solar activity would have leveled off – bearing in mind that the solar peak was actually in the late 1950s (rather than 1940). And do you think that the warming would have continued at the pre-1940 rate.

  46. 246
    Martin Lewitt says:

    Re: Ike Solem #232,

    I don’t make a blanket claim that the recent warming is due to the solar activity that has been maintained since the early 20th century although it strains credulity to suggest that these unusually high activity levels are a mere unrelated coincidence. Your Pinatubo argument doesn’t hold water. That is an example of negative aerosol forcing, not solar forcing. While aerosols act through modulating solar energy, the variation in distribution of that energy that they cause is a different coupling to the climate than results from variation in external solar forcing. If we want to know how much of the recent warming should be attributed to solar, we need better models, just as we do for GHGs.

    The climate commitment studies show that the climate system response to new levels of forcing takes decades and centuries. Just as the level of solar forcing did not disappear during the Pinatubo event, it also persisted through the midcentury cooling event. The longer duration of the midcentury cooling does not make a qualitative difference, although subjectively, one may want to attribute the recent temperature rise to global brightening, rather than solar or GHG forcing, since global brightening is more directly responsible for the dramatic shape of the temperature curve, the ultimate source of the warming that makes the temperatures achieved more unusual in the historical and paleo record context is the unusual levels of solar activity and GHG forcing.

    I suspect that we don’t really understand the mid century cooling event. It was a time of significant aerosol and particulate pollution, three major conflicts WWII, Korea and Vietnam, open air nuclear testing, leaded gasoline, etc. I suspect that each of these contributed unique elements that we haven’t really been able to assess with the latest instrumentation. For instance, the short period of open air nuclear testing injected levels of tritium into the stratosphere, that did not drop to normal levels through precipitation and decay until the 1980s. I haven’t seen a lot of analysis of the radiative forcing of lead particulates, and the peak usage and eventual phase out of leaded gasoline rather neatly overlaps with this time period. The cleanup of sulfates contributing to acid rain, and the fall in communist block economic activity all coincided with the end of the cooling period. So, in a very real sense the recent warming probably is anthropogenic, but in a temporary way that doesn’t project into the future beyond the climate commitment that was masked or unveiled by this one period.

  47. 247
    Ike Solem says:

    RodB,

    It is true that the Bush Administration has censored many reports from government agencies on global warming, but that doesn’t change the reliability of the science, does it? Are you going to argue that the warming and melting in the Arctic has NOT outstripped all the predictions of the climate models?

    Generally speaking, if a computer model fails to predict something accurately, people then start looking for what the model missed – that’s true in any area of science and engineering – airplane wing design, say. Actually, models are more useful when they fail because they show you what it is you’re missing.

    There is a long record of this administration censoring government scientists and reports, which was the subject of a House hearing – see here.

    Another, more recent example is the gross editing of a CDC report on global warming: Full Version of White House “Edited” CDC Climate Report – with highlights!

    These were not minor edits the White House PR spin machine would like us to believe. The word-count for the CDC Director’s Senate testimony went from 3,107 to 1,500 after the White House got through with it.

    Whole sections on health related effects to extreme weather, air pollution-related health effect, allergic diseases, water and food-borne infectious diseases, food and water scarcity and the long term impacts of chronic diseases and other health effects were completely wiped out of the testimony.

    There are many examples:
    Bush Aide Softened Greenhouse Gas Links to Global Warming

    A White House official who once led the oil industry’s fight against limits on greenhouse gases has repeatedly edited government climate reports in ways that play down links between such emissions and global warming, according to internal documents.

    Thus, it’s not too surprising that the White House also censored the Pentagon report on global warming, is it? That allows people such as yourself to claim “these government branches have no official position on global warming”, which is probably why it’s done.

  48. 248
    Hank Roberts says:

    No question many of the scientists in the Navy may have wanted the research to be publicly available. The Navy has published much more climate work; I’ve been finding and pointing to links to thesis publications for example for some years.

    That particular NSF Press Release that Gavin links to is not available any longer. Pity. I’m sure I cited it recently as well.

    Google still has the text in its cache, here:

    http://www.google.com/search?q=cache:VOVB9J0dpq8J:www.nsf.gov/news/news_summ.jsp%3Fcntn_id%3D102863+%22gore+box%22+%22vice+president%22+%22press+release%22&hl=en&ct=clnk&cd=3&gl=us&lr=lang_en&client=firefox-a

    NOTE — I argue against hiding links to references behind hilighted words. Sure, it’s shorter. But IF you hide the actual citation behind a hilighted word, then later — when the ref. disappears — most people won’t know how to search for that reference.

    Lest it be lost, if our hosts don’t mind — here’s the full text:

    ——begin——-

    Press Release 98-006
    Newly Declassified Submarine Data Will Help Study of Arctic Ice
    Map of Gore Box

    http://www.nsf.gov/news/mmg/media/images/pr986_f.jpg

    Map of Arctic Ocean where formerly classified submarine data are now being released for study.
    Credit and Larger Version should be clickable download from http://www.nsf.gov/news/news_images.jsp?cntn_id=102863&org=NSF

    January 28, 1998

    This material is available primarily for archival purposes. Telephone numbers or other contact information may be out of date; please see current contact information at media contacts.

    A treasure-trove of formerly classified data on the thickness of sea ice in the Arctic Ocean, gathered by U.S. Navy submarines over several decades, is now being opened. Data from the first of approximately 20 cruise tracks — an April, 1992 trans-Arctic Ocean track — has just been released, and information from the rest of these tracks, or maps of a submarine’s route, will be analyzed and released over the next year-and-a-half.

    “The data opens up a magnificent resource for global change studies,” said Mike Ledbetter, National Science Foundation (NSF) program director for Arctic system science.

    Climate modellers differ over the fate of the great expanse of Arctic sea ice, which is about the size of the United States. More than half the ice melts and refreezes each year.

    “The Navy has collected data for decades on ice thickness in the Arctic, which was important to know for navigation and defense,” said Ledbetter. “But this information is also extremely important to science, now giving us a history of sea ice that we could not collect any other way.”

    “The data is essential to building a baseline of sea-ice thickness in the Arctic basin to examine how global change affects ice cover,” explained Walter Tucker of the U.S. Army Cold Regions Research and Engineering Laboratory. Tucker is supported by NSF to process and analyze all digital ice-draft data collected by Navy submarines in the Arctic since 1986. The National Snow and Ice Data Center at the University of Colorado-Boulder is handling the actual data release.

    The Arctic Submarine Laboratory, on behalf of the Chief of Naval Operations, approved declassifying the sea-ice data within a specific swath of the Arctic Ocean, roughly between Alaska and the North Pole. The area is known as the “Gore Box” for Vice President Al Gore’s initiative to declassify Arctic military data for scientific use.

    The data will provide a historical context for current, more intensive studies of Arctic ice by the Surface Heat Budget of the Arctic Ocean (SHEBA) project, in which NSF has frozen a ship into the ice to serve as a floating science platform for 13 months. SHEBA’s aim is to chart the fate of the pack ice, ultimately improving predictions of global change.

    ——-end——–

  49. 249
    Mr Henderson says:

    I must express my admiration for the patience of those who have worked to improve Tom Watson’s understanding.

  50. 250
    Jim Eager says:

    No apologies needed, Tim. Rereading my first paragraph simplifying the greenhouse effect, the confusing wording is all too glaring now.
    As for my patience, Stephen was polite in his post and his desire for answers to his questions seemed sincere, and I’m inclined to give that kind of post the benefit of the doubt. I’m way out of my league here in many discussions, but it’s thanks to those of you who are so willing to share your expertise and add to the reading list that I’ve acquired a much better grasp of the basics.


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