Open Mind

Feedback

April 4, 2008 · 122 Comments

If earth were nothing but a big ball of rock, then computing the effect of changes in energy balance on our planet’s temperature would be easy. That’s because the only relevant factors would be the shortwave (SW) solar energy coming in, and the longwave (LW) radiation escaping to space, and we’ve got a good handle on that. The Stefan-Boltzmann radiation law enables us to compute that for near earth conditions, an additional 1 watt per square meter (W/m^2) of energy coming in to the planet would increase temperature by about 0.3 deg.C. This is the climate sensitivity to radiative forcing, which is the temperature change due to an additional 1 W/m^2 of climate forcing. It’s not the same as the climate sensitivity to doubling CO2; doing that would increase radiative forcing by around 4 W/m^2, so climate sensitivity to doubling CO2 would be around 4 times greater, about 1.2 deg.C. (Note: this is based on a global average temperature of about 14 deg.C, which is a real-world value, but if earth had no atmosphere it would be considerably cooler and climate sensitivity would be a bit less.)

But: earth has an atmosphere, and oceans, and ice caps, and glaciers, and plants and animals and people, oh my! As a result, the response of the climate system to additional climate forcing is quite a bit more complicated. Temperature change can alter other factors which themselves affect climate forcing, which in turn affects temperature, in a feedback loop. Because of these feedbacks, it becomes difficult to estimate with precision exactly how climate responds to climate forcing because it can be difficult to estimate the feedback factors with precision. Let’s consider some of the known factors, and estimates of their impact on climate sensitivity.


Ice and Snow Albedo Change

One of the most clear-cut is albedo feedback; albedo is the reflectivity of the earth. Some of the incoming solar energy never enters the climate system at all; it’s not absorbed then re-radiated, it doesn’t drive climate, it simply bounces right back to space. The fraction of incoming solar energy which is scattered back to space is earth’s albedo, and is just about 0.3 (so 30% of incoming solar energy is reflected away).

As the climate warms, snow and ice tend to reduce. But snow and ice are much more reflective than land and open ocean. Hence climate warming tends to reduce highly reflective snow and ice, and therefore reduce albedo. Reduced albedo means more incoming solar energy is absorbed into the climate system, warming the planet even further, so ice/snow albedo is a positive feedback, i.e., one which tends to amplify rather than reduce warming.

Sea ice has another affect, that it’s a good insulator. So when sea ice disappears, it enables more heat to escape from the open water. Hence the disappearance of sea ice when the surface is in darkness can actually cool the region, whereas in solar illumination it tends to warm. The greatest warming occurs when a region loses its sea ice when illuminated but recovers it when in darkness. This makes the north polar region most susceptible to ice-albedo feedback; if the north polar ice cap is absent in summer but recovers in winter, the net warming of the polar climate will be substantial. This is one of the main reasons that the north polar region shows so much more warming than the rest of the world. The south polar region is covered by land (Antarctica) and its ice cap is vastly thicker than the sea ice in the north, so in the south polar region the effect is not nearly so great.

The northern hemisphere also has far more land than the southern, particularly in latitudes near to, but not in, the polar region. Hence the northern hemisphere is also much more susceptible to snow-albedo feedback. The southern hemisphere simply doesn’t have nearly as much land area which even can be covered by snow, so variations of snow aren’t nearly so great and snow-albedo feedback isn’t as great a factor.

All of which means that polar amplification is vastly greater for the northern hemisphere than the southern. This has been clearly established by surface temperature measurements, and is also supported by climate models. Here’s the temperature change (normalized so the global average is 1 unit) over a century as a function of latitude (south to the left, north to the right) according to climate models used for the 4th Assessment Report (AR4) of the IPCC (from Bony et al. 2006, J. Climate, 19, 3445):

latitude.jpg

Only slight amplification is indicated in the south polar region but great amplification is indicated in the north, in accord with observations of surface temperature over the last several decades. There’s no doubt, either theoretically or observationally, that snow/ice albedo feedback is a positive one (increasing warming), and that it affects the north polar region most strongly.

Both historical and satellite observations unambiguously demonstrate a strong trend of decrease in northern hemisphere sea ice, especially in the summer season, and historical data indicate a long-term, but no recent, reduction of southern hemisphere sea ice. Observations also indicate a declining trend in northern hemisphere snow cover.

Water Vapor and Lapse Rate

Basic physics (the Clausius-Clapeyron equation) indicates that as temperature increases, the amount of wator vapor in the air should also increase. In fact it’s likely to do so in such a manner that absolute humidity (the water vapor content of the air) increases while relative humidity (the fraction of saturation level) remains roughly constant. The increase of water vapor content in the atmosphere over the last several decades has been confirmed observationally (Santer et al. 2007, PNAS, 104, 15248; Mieruch et al. 2007, Atmos. Chem. Phys. Discuss., 7, 11761).

Water vapor is an important greenhouse gas, so more of it in the atmosphere should lead to greater greenhouse warming; hence increased wator vapor is a positive feedback due to its radiative effect; this is often called the water vapor (WV) feedback. But water vapor has another impact; it’s responsible for the lapse rate of the atmosphere being different from its value for a dry atmosphere. The lapse rate (LR) is the rate at which temperature changes with altitude in the atmosphere. It tends to follow the moist adiabat rather than the dry adiabat, because of the impact of water vapor; increases in water vapor tend to reduce the lapse rate, although water vapor isn’t the only influence. If the LR increases, it will tend to increase surface warming, but if it decreases it’ll decrease surface warming.

Computer models indicate that the impact of LR will be a negative feedback in the tropics but a positive feedback outside the tropics, and that the global effect will be negative. They also indicate that the positive feedback from the radiative effect of water vapor (WV) is larger than the LR negative feedback, so the net effect is a strong positive feedback in the climate system. In addition, models which show greater WV positive feedback also tend to show greater LR negative feedback, as expcted, so the uncertainty in combined WV+LR feedback is less than that of either factor alone.

Clouds

The feedback effect of clouds is the one least well understood, and for which different computer models give the greatest uncertainty. Clouds are a positive feedback for their LW (long-wave) radiative effect because of absorption and emission of infrared radiation, but a negative feedback for their SW (short-wave) radiative effect because they reflect incoming sunlight back to space; the reflectiveness of clouds makes them a potent influence on earth’s albedo. They also affect the circulation of the atmosphere and the distribution of areas with lots of water vapor compared to drier regions.

Computer models estimate the total feedback effect from changes in cloud dynamics is another positive feedback. Observations indicate a reduction of cloudiness, especially in the tropics, and satellite data clearly indicate that the global albedo is declining (Wielicki et al. 2005, Science, 308,825). Nonetheless, the cloud feedback has the highest level of uncertainty in climate models.

Other Feedbacks

There are other feedbacks, but they are generally not yet included in computer model simulations. For example, warming of the oceans will lead to the release of dissolved CO2 from seawater, increasing atmospheric CO2 and causing further warming — another positive feedback. It may also lead to the disintegration of methane clathrates, releasing large quantities of methane (an even more potent greenhouse gas per molecule) into the atmosphere. The melting of permafrost likewise threatens to release vast quantities of CO2, as does the desertification of forest areas like the Amazon rain forest. Changes of land use and plant distribution affect earth’s albedo, so changes in the biosphere may constitute another climate feedback. Generally, the feedbacks unaccounted for in computer model simulations tend to be strongly positive feedbacks, but their likely magnitude, and especially the time scales on which they operate, are uncertain.

Total Feedback Estimates

Estimates of total feedback in the climate system are very strongly positive; they’re well summarized in Bony et al. (2007):

feedback.jpg

The only negative feedback is the lapse rate (LR), and it’s dominated by the many positive feedbacks. As stated earlier, the feedbacks not included in this figure tend to be positive.

Uncertainty in Climate Sensitivity

Of course estimates of the magnitude of climate feedbacks, like all scientific estimates, are uncertain. There’s even greater uncertainty in their impact on climate sensitivity, because sensitivity depends on feedback in a nonlinear fashion. If each degree of warming leads, through feedback, to another f degrees of warming, then f is the feedback factor. That addition warming will itself trigger feedbacks, leading to f \times f degrees more warming. And that will lead to f \times f \times f degrees, etc., etc. The total impact of a feedback factor f is therefore to multiply the externally-caused warming by a gain factor

G = 1 / (1-f).

If the feedback is positive, and our estimate of the feedback factor f is only a little in error, the estimate of the gain factor can be very much in error. Most of that error is on the high side; it’s much easier to get an accurate lower limit to climate sensitivity than an accurate upper limit. That’s one of the reasons that it’s so hard to pin down climate sensitivity estimates with precision, and one of the reasons different estimated ranges tend to show much less “spread” on the lower limit than on the upper limit.

All in all, the existence of feedbacks cannot be denied, and the evidence is overwhelming that the bulk of their impact will be to amplify warming, not to suppress it. The precise amount of amplification remains uncertain, and the resultant climate sensitivity even more so. But considering that the greatest uncertainty is not whether sensitivity may be much less than current estimates, rather it’s whether sensitivity may be much more than current estimates, is hardly a reassuring thought. The uncertainty in feedbacks, and in sensitivity, is no comfort; rather it’s cause for greater concern.

Categories: Global Warming · climate change

122 responses so far ↓

  • kim // April 4, 2008 at 3:22 pm

    What about feedback effects in the oceanic oscillations. The Argo data is showing, among other things, that various processes in the oceans are not well enough understood to validate present models. Considering that the oceans hold a large amount of heat, isn’t this a serious flaw?
    ===========================

    [Response: Compare and contrast the words "oscillation" and "trend."]

  • Ian // April 4, 2008 at 4:35 pm

    Tamino, thanks for an excellent overview. A quick question: Elsewhere I’ve seen reference to “fast” feedbacks (e.g., sea ice, clouds, water vapor) and “slow” feedbacks (e.g., ice sheets, land use), with sensitivity estimates normally based on the fast feedbacks alone. Do the surface albedo estimates that you’ve shown above include slow feedback estimates (e.g., for ice sheets)?

    [Response: No, they don't. Computer models don't indicate much mass wasting of ice sheets in Greenland or Antarctica over the next century, although recent research indicates that's a possibility. I think James Hansen has considered the greater sensitivity which would ensue from "slow" feedbacks.]

  • nanny_govt_sucks // April 4, 2008 at 4:43 pm

    All in all, the existence of feedbacks cannot be denied, and the evidence is overwhelming that the bulk of their impact will be to amplify warming, not to suppress it.

    What “evidence”? You’ve talked about computer models. Computer models do not produce evidence.

    Have you had a look at the DATA coming from the NASA Aqua satellite? There are some that are saying it shows feedbacks are 0 or negative. From http://www.theaustralian.news.com.au/story/0,25197,23411799-7583,00.html

    Duffy: “Can you tell us about NASA’s Aqua satellite, because I understand some of the data we’re now getting is quite important in our understanding of how climate works?”

    Marohasy: “That’s right. The satellite was only launched in 2002 and it enabled the collection of data, not just on temperature but also on cloud formation and water vapour. What all the climate models suggest is that, when you’ve got warming from additional carbon dioxide, this will result in increased water vapour, so you’re going to get a positive feedback. That’s what the models have been indicating. What this great data from the NASA Aqua satellite … (is) actually showing is just the opposite, that with a little bit of warming, weather processes are compensating, so they’re actually limiting the greenhouse effect and you’re getting a negative rather than a positive feedback.”

    [Response: I talked about a helluva lot more than just computer models:

    Both historical and satellite observations unambiguously demonstrate a strong trend of decrease in northern hemisphere sea ice, especially in the summer season, and historical data indicate a long-term, but no recent, reduction of southern hemisphere sea ice. Observations also indicate a declining trend in northern hemisphere snow cover.

    The increase of water vapor content in the atmosphere over the last several decades has been confirmed observationally (Santer et al. 2007, PNAS, 104, 15248; Mieruch et al. 2007, Atmos. Chem. Phys. Discuss., 7, 11761).

    Observations indicate a reduction of cloudiness, especially in the tropics, and satellite data clearly indicate that the global albedo is declining (Wielicki et al. 2005, Science, 308,825).

    First: anything from Jennifer Marohasy is unreliable. Second: learn to read.]

  • Elery Fudge // April 4, 2008 at 4:44 pm

    We could probably learn more about albedo and radiation loss to space at all wave lengths. It would be nice to have a satellite such as the Triana launched to L1 to measure all emitted radiation. A second satellite to continuously monitor radiation loss from the dark side would also be valuable.

  • Barton Paul Levenson // April 4, 2008 at 5:05 pm

    Amen to Elery’s comment. More satellites, more instruments. Hopefully the next administration will be less prone to suppress space climate research.

  • nanny_govt_sucks // April 4, 2008 at 5:28 pm

    My apologies for briskly skimming your article.

    Basic physics (the Clausius-Clapeyron equation) indicates that as temperature increases, the amount of wator vapor in the air should also increase. … The increase of water vapor content in the atmosphere over the last several decades has been confirmed observationally (Santer et al. 2007, PNAS, 104, 15248; Mieruch et al. 2007, Atmos. Chem. Phys. Discuss., 7, 11761).

    Look at Santer et al 2007 figure 1. Observations show no trend, then a jump in 1998, then a decline since then. This is hardly consistent with global average temperature data.

    [Response: You're applying the same "see only what you want to see" approach to Santer, that you did to my post.

    The observations are *entirely* consistent with global temperature data. The "no trend" from 1988 to 1997 is consistent with temperature, as impacted by the Mt. Pinatubo explosion. The jump in 1998 is completely consistent with the similar temperature increase due to the giant el Nino, as is the decline afterward to higher-than-pre-1997 levels. Look also at Mieruch et al., the temperature-WV connection is as plain as the nose on my face.

    Only trolls like you believe that the temperature-WV connection is anything less than clear. It's time for me to take fred's advice and cut the trolls loose.]

  • Paul Middents // April 4, 2008 at 5:48 pm

    n_g_s cut and paste of Mahorasy is the second time recently I’ve been afflicted by this bit of denialist misinformation. A local know nothing columnist regurgitated the same thing.

    This seems to have roots in the 2004 NASA Goddard release:

    http://www.nasa.gov/centers/goddard/news/topstory/2004/0315humidity.html

    This relates to the 2004 work of Minschwaner and Dessler:

    http://www.met.tamu.edu/people/faculty/dessler/dessler04.pdf

    From the abstract:

    “The analysis suggests that models that maintain a fixed relative humidity above
    250 mb are likely overestimating the contribution made by these levels to the water vapor feedback.”

    Gavin Schmidt commented in Real Climate that this study only looks at tropical effects high in the troposphere which are unlikely to have a large impact on the overall climate.

    Following the work forward, Minschwaner and Dessler report in 2006:

    http://www.met.tamu.edu/people/faculty/dessler/minschwaner2006.pdf

    From the abstract:

    “Furthermore, the implied feedback in the models is not as strong as would be the case if relative humidity remained constant in the upper troposphere. The model mean decrease in relative humidity is _2.3% _ 1.0% K_1 at 250 mb, whereas observations indicate decreases of _4.8% _ 1.7% K_1 near 215 mb. These two values agree within the respective ranges of uncertainty, indicating that current global climate models are simulating the observed behavior of water vapor in the tropical upper troposphere with reasonable accuracy.”

  • Wade Michaels // April 4, 2008 at 6:06 pm

    Whenever this issue comes up, I always feel torn. We currently know some of the positive feedbacks involved and some of the negative feedbacks…and we’re learning more every day.

    But inasmuch as the current science lends itself to a runaway scenario, I just can’t bring myself to completely accept it. It seems counterintuitive. (or ignorant, if you will).

    We know the earth has SOME sort of overpowering negative feedback because we’ve had multiple glaciations. But what? when? how?

    I can’t help thinking that the models should at least account for this somehow (although that would completely bias them).

    Something similar to Einstein’s anti-gravity fudge factor…a climatological constant.

    Thoughts?

    [Response: I think you're operating under the misconception that feedback leads to a runaway scenario. It doesn't, and there's no need to invoke any unknown feedback (positive or negative) to limit the temperature excursions during glacial cycles.]

  • Wade Michaels // April 4, 2008 at 6:07 pm

    By ignorant, I mean…ignorant on my part.

  • Hank Roberts // April 4, 2008 at 6:31 pm

    Wade, “rate of change”
    Look up “biogeochemical cycling” — that’s what’s known about natural processes. Then look at the rate of change during the last couple of centuries — it’s about 100x as fast, on the one variable we are controlling (atmospheric CO2).

    Here’s one recent interesting abstract (follow the citation links for more)
    http://icesjms.oxfordjournals.org/cgi/content/abstract/fsn008v1

  • David B. Benson // April 4, 2008 at 6:33 pm

    Once again, nicely done Taminno!

  • Chris Colose // April 4, 2008 at 6:36 pm

    Roger Pielke made a similar comment on my blog in the post “How not to discuss the Water Vapor feedback” about WV not changing much since 1998. It is also well acknowledged by skeptics that “global warming stopped in 1998.” Weird, eh? Taking the anomalous ‘98 year as a start point is always curious, but if you do that then the temperature rise has not been incredibly significant, but still clearly positive. The response to Mt. Pinatubo provides a real-world confirmation of our understanding of WV feedback (see Tony Del Genio’s article in Science entitled “the dust settles on water vapor feedback.”)

    As for clouds, they are a large reason for the range between 2 to 4.5 C for a doubling of CO2. As noted by Tamino, models have cloud feedbacks ranging from neutral to strongly positive. It doesn’t look like much room for a strong negative one, because we have data showing low cloud cover (they control the albedo more than any other kind) decreasing as it gets hotter. More discussion in Bony et al. (how well do we understand…) and work by Soden and Held, and the NAS report on feedbacks.

    To Wade– plug in a feedback factor < 1 into the equation by Tamino and you’ll find that the series of feedbacks converges at a point that does not lead to a runaway effect. Another option is to have something reverse the trend.

  • Gavin's Pussycat // April 4, 2008 at 8:02 pm

    Wade, glaciations do not require a negative feedback — they require a negative forcing, which may then be amplified by a positive feedback (or diminished by a negative one).

    The recent cycle of ice ages and interglacials has been convincingly related to astronomical forcing in the form of variations in Earth axis tilt and orbital eccentricity (google for Milankovich), helped by some positive feedbacks (like albedo). What pushed the Earth into this regime originally has been speculated to be increased rock weathering (absorbing CO2) due to the rise of the Himalayas (a negative forcing!).

    And then there are the “Snowball Earth” episodes — separate, long story :-)

  • DocMartyn // April 4, 2008 at 10:07 pm

    “The Stefan-Boltzmann radiation law enables us to compute that for near earth conditions, an additional 1 watt per square meter (W/m^2) of energy coming in to the planet would increase temperature by about 0.3 deg.C.”

    Just how does it do that in an atmosphere which contains water present in three phases?

    [Response: People who don't bother to read are getting really annoying. That means you.

    What part of "If earth were nothing but a big ball of rock" is unclear? What part of "But: earth has an atmosphere, and oceans, ..." in the *next* paragraph is unclear?]

    Does the Stefan-Boltzmann equation deal with the relationship between air pressure, humidity and temperature?
    An what is the effect of the earth rotation? I cannot be notice you have not attempted to model the Diurnal cycle. It is somewhat complicated, but can you explain the three day changes in Temperature we observe here:-

    http://www.net-weather.org/outside_temperature.html

    [Response: The *average* temperature of a rotating solid mass, over the entire globe, is very well approximated by balancing the incoming solar irradiance with outgoing longwave radiation according to the Stefan-Boltzmann equation.]

  • Dave Andrews // April 4, 2008 at 10:40 pm

    “Computer models don’t indicate much mass wasting of ice sheets in Greenland or Antarctica over the next century, although recent research indicates that’s a possibility”

    So what exactly does this mean - “I’m hedging my bets, actually though I don’t really know”

    [Response: No, it means that computer models don't indicate much mass wasting of ice sheets in Greenland or Antarctica over the next century, although recent research indicates that's a possibility.

    Your comment is NOTHING BUT SNARK. Thank you for confirming that deleting garbage comments isn't just a good idea, it's necessary.]

  • TCO // April 4, 2008 at 11:13 pm

    Please don’t delete snark commentsJust delete commercial spam.

    [Response: There are comments that have some snarky elements, and there are comments that are nothing but insult with no substantive content whatsoever. The latter are going into the trash bin. The former may as well, it's at my discretion.

    There are also comments that sling mud but just show the writer simply hasn't bothered to read what's in the post. Those too are destined for deletion.]

  • Bob North // April 4, 2008 at 11:41 pm

    HB - very nice description of some of the various feedback mechanism. Particularly, your explanation of why the north pole is showing so much more warming than the south pole is clear and very easy to understand. I do have a couple of questions though.

    On the sea ice/ enhanced warming factor, is my understanding correct that the reason that the enhanced warming is greatest when you lose increasing amounts of ice in the summer (illumination period) and gain it back in the winter (darkness) is that the newly-formed sea ice acts as an insulator and basically keeps the ocean from losing its newly-gained heat during the winter months?

    Second, with respect to the calculated 0.3 degree climate sensivity for each W/m^2 of additional radiative forcing, since this is based on the Stefan-Bolzman equation for a black body and earth is neither a black body or even a gray body, shouldn’t there be some plus/minus amount on that number (e.g., 0.3 deg +/- 0.05 deg.). I don’t doubt that the Stefan Baltzmann law provides a good estimate of the inherent climate sensitivity, but it does seem that it can’t be exact.

    Regards,
    Bob North

    [Response: Yes, the sea ice which re-forms acts as an insulator to hold heat in the ocean.

    Bear in mind that application of Stefan-Boltzmann applies to the airless, oceanless ball of rock. Also, the emissivity tends to be equal to the absorptivity, so those factors cancel each other out, making Stefan-Boltzmann an excellent approximation for a rapidly rotating solid body.]

  • Geoff Larsen // April 5, 2008 at 12:06 am

    Chris Colose wrote
    “As for clouds, they are a large reason for the range between 2 to 4.5 C for a doubling of CO2. As noted by Tamino, models have cloud feedbacks ranging from neutral to strongly positive. It doesn’t look like much room for a strong negative one, because we have data showing low cloud cover (they control the albedo more than any other kind) decreasing as it gets hotter. More discussion in Bony et al. (how well do we understand…) and work by Soden and Held, and the NAS report on feedbacks”.

    But what is the cause and what is the effect.

    Roy Spencer has submitted a paper to the Journal of Climate. From a post by Roy Spencer on Roger Pielke Snr’s blog, Dec 30, 2007 “Cause versus Effect in Feedback Diagnoses by Roy W Spencer”.

    http://climatesci.org/2007/12/30/update-cause-versus-effect-in-feedback-diagnosis-by-roy-w-spencer-12302007/

    “On August 8, 2007, I posted here a guest blog entry on the possibility that our observational estimates of feedbacks might be biased in the positive direction. Danny Braswell and I built a simple time-dependent energy balance model to demonstrate the effect and its possible magnitude, and submitted a paper to the Journal of Climate for publication.

    The two reviewers of the manuscript (rather uncharacteristically) signed their names to their reviews. To my surprise, both of them (Isaac Held and Piers Forster) agreed that we had raised a legitimate issue. While both reviewers suggested changes in the (conditionally accepted) manuscript, they even took the time to develop their own simple models to demonstrate the effect to themselves.

    Of special note is the intellectual honesty shown by Piers Forster. Our paper directly challenges an assumption made by Forster in his 2005 J. Climate paper, which provided a nice theoretical treatment of feedback diagnosis from observational data. Forster admitted in his review that they had erred in this part of their analysis, and encouraged us to get the paper published so that others could be made aware of the issue, too.

    And the fundamental issue can be demonstrated with this simple example: When we analyze interannual variations in, say, surface temperature and clouds, and we diagnose what we believe to be a positive feedback (say, low cloud coverage decreasing with increasing surface temperature), we are implicitly assuming that the surface temperature change caused the cloud change — and not the other way around.

    This issue is critical because, to the extent that non-feedback sources of cloud variability cause surface temperature change, it will always look like a positive feedback using the conventional diagnostic approach. It is even possible to diagnose a positive feedback when, in fact, a negative feedback really exists.

    I hope you can see from this that the separation of cause from effect in the climate system is absolutely critical. The widespread use of seasonally-averaged or yearly-averaged quantities for climate model validation is NOT sufficient to validate model feedbacks! This is because the time averaging actually destroys most, if not all, evidence (e.g. time lags) of what caused the observed relationship in the first place. Since both feedbacks and non-feedback forcings will typically be intermingled in real climate data, it is not a trivial effort to determine the relative sizes of each“.

  • P. Lewis // April 5, 2008 at 12:39 am

    Tamino said

    The south polar region is covered by land (Antarctica) and its ice cap is vastly thicker than the sea ice in the north, so in the south polar region the effect is not nearly so great.

    To put some bones on that: the mean elevation of the north polar region is essentially sea level (ice thickness about 3 m or so max.), whereas Antarctica has a mean elevation of ~2 km; bed elevations range from ~2.5 km below sea level (Bentley Trench), to ~50 m below sea level (South Pole) to ~1.6 km above sea level (Dome A); mean ice thicknesses are ~1.3 km in WA and ~ 2.2 km in EA.
    [Figures culled from a BAS factsheet pdf for which I've lost the link.]

  • TCO // April 5, 2008 at 12:40 am

    [Response: There are comments that have some snarky elements, and there are comments that are nothing but insult with no substantive content whatsoever. The latter are going into the trash bin. The former may as well, it's at my discretion.

    There are also comments that sling mud but just show the writer simply hasn't bothered to read what's in the post. Those too are destined for deletion.]

    Please don’t delete any of these either. (I am behaving my usual butt-manly troll self. But would prefer to rip the [edit] Make them cry. Humiliate them. Hurt them like kids on the playground.)

    [Response: Then maybe you should start your own blog.

    I'm getting tired of having to deal with garbage everywhere. I'm also tired of seeing the *same* garbage again and again. I'm especially annoyed at comments whose only purpose is to embarrass me and/or climate science, which only indicate staggering ignorance, but if left unanswered might actually serve that vile purpose. They contribute nothing but confusion. It's gonna stop, because those people will get tired of seeing their comments vanish into nothingness.]

  • Lost and Confused // April 5, 2008 at 1:12 am

    Tamino, in light of your responses to TCO here, would you be willing to review Open Thread? There is a number of posts that would belong in the trash bin by those standards. I am not sure how much you noticed this, but the garbage is not limited to one “side” of this discussion.

    More importantly, and I do not mean this as an insult, but both you and many other posters here have misrepresented MM’s work. This problem can be seen in the discussion of WA in Open Thread. I dislike being critical of a host, but your mistake is the same mistake made by many of the posters. As such, you are somewhat responsible. I hope a meaningful discussion can arise, as I value nothing more than the truth.

    Also, I apologize for posting this here, as it is not topical. Feel free to delete it if you wish, I just thought it would be easier for you to see it here.

    [Response: I won't remove comments after having allowed them.

    You think I and others have misrepresented MM, we diagree. I don't intend to stifle disagreement, and when it comes to the MBH98 discussion on the open thread I haven't taken sides in moderating comments. When arguments arise, passions are inflamed, and it's a fine line between allowing passionate, even angry disagreement, and rejecting what's too inflamatory.

    But anyone can see that there are comments -- on this very thread, and elsewhere too -- which don't fall into the category of disagreement or even passionate angry insulting disagreement. They're just stupid. That stuff has got to stop. And I reserve the right to delete other comments that I find offensive. But the main thrust of my comment is, that I'm rejecting the stupid stuff.]

  • Lost and Confused // April 5, 2008 at 1:32 am

    I understand the point of not deleting posts you have allowed, and I agree. I mainly mentioned it to highlight there is garbage beyond that aimed at the “consensus” position. Neither “side” is perfect.

    [Response: No disagreement about that.]

  • Aaron Lewis // April 5, 2008 at 1:49 am

    I think the importance of fresh water floating on seawater in the formation of sea ice is understated. My expectation is that one of the first signs of significant Antarctic Ice Sheet melt would be a sudden increase in sea ice area around Antarctica as the freezing point at the sea’s surface increased from -1.8C to 0C. This would enhance SH warming.

    I am also concerned that anthropogenic particular haze is interfering with estimates of climate sensitivity to CO2 and other greenhouse gases. If anything disrupted the production of our haze, increased atmospheric clarity could cause an unpleasant surge in the rate of warming from GHG already in the air.

    The above two items are not meant in any way to be criticism of this excellent post, but to reinforce your thesis that the climate system is complex enough to be interesting, and worth diligent study.

  • fred // April 5, 2008 at 7:05 am

    The argument is logically fairly simple. It is that any small rise in temperature however caused will trigger larger rises. We then have what may be a partial or a complete list of feedbacks both positive and negative that result in this. None are specific to CO2 based warming. Any warming of the required amount, however caused, ought to do it if the argument is correct.

    So its natural to look back at the climate record and ask whether this two stage warming has in fact happened in the past. If you look at the Hadley or GISS charts of anomalies, the temperature rise between 1910 and 1940 seems to be roughly comparable in size and speed to the recent warming, and the overall temperature in the thirties was not too different. Its hard to be sure about Roman and Medieval warmings, but probably they were as warm as today - maybe they were slower. Whatever, the rate should not matter, its the actual temperature that is supposed to trigger the subsequent warmings, isn’t it?

    It seems we have a series of natural experiments, and I’m not clear what the argument says happened during them. Did the earlier warmings for some reason fail to trigger the feedbacks? Was there some cooling trigger, and if so what, and how did it work? Was the issue that the absolute temperature was not high enough to activate the feedbacks? Or is the presence of CO2 producing continuous warming, and that’s what is hypothesized to activate the feebacks, as opposed to some more transient causes in the past.

    That would be a valid argument but one would like to know what exactly the past transient causes were before accepting that they were relevantly different.

    Comments?

    [Response: I'll make a couple. First, there's really not evidence that medieval or Roman times were as warm as today, the evidence is to the contrary. Second, we just don't have enough data about prior changes in water vapor or cloudiness, and as far as I can tell no data at all about changes in the lapse rate.

    We do have undeniable evidence about one of the feedbacks during the very distant past, the ice age cycles: the disappearance of ice sheets. Those long-gone times also give evidence of one of the "other" feedbacks, the warming-induce release of CO2 from the oceans.]

  • David B. Benson // April 5, 2008 at 4:51 pm

    Bob North Looking into

    http://en.wikipedia.org/wiki/Climate_model

    at the zero-dimensional model, the Stefan-Boltzman factor is multiplied by an ‘effective emmisivity’ to account for global warming gases.

  • Timothy Chase // April 5, 2008 at 4:53 pm

    Chris Colose wrote:

    As noted by Tamino, models have cloud feedbacks ranging from neutral to strongly positive. It doesn’t look like much room for a strong negative one, because we have data showing low cloud cover (they control the albedo more than any other kind) decreasing as it gets hotter.

    Cloud cover diminishing in the tropics, beginning with the lower altitudes, and presumably this could be an “Iris Effect” where the rate at which longwave (thermal) radiation escapes increases due to a reduced cloud greenhouse effect, resulting in a negative feedback.

    However, the reduction in cloud cover has almost exactly balanced this with the increased absorption of shortwave radiation as shown by the diminished earth albedo — over the past couple decades. Less sunlight is being reflected by the clouds and thus more sunlight is being absorbed at the surface, and thus the net effect of the reduction in clouds is neutral.

  • chriscolose // April 5, 2008 at 6:05 pm

    Geoff,

    I’ve not seen a published paper that really calls into question that clouds can act as a feedback to changes, or one that really argues that cloud changes are occurring by themselves today an forcing modern global warming. I’m more skeptical about things coming from Roy Spencer (because I learned the boy who cried wolf story when I was little), but if there is a peer-reviewed reference out there that provides convincing evidence for such mechanism, I’m all ears

  • Ken Feldman // April 5, 2008 at 6:42 pm

    Fred wrote:

    “So its natural to look back at the climate record and ask whether this two stage warming has in fact happened in the past. If you look at the Hadley or GISS charts of anomalies, the temperature rise between 1910 and 1940 seems to be roughly comparable in size and speed to the recent warming, and the overall temperature in the thirties was not too different. Its hard to be sure about Roman and Medieval warmings, but probably they were as warm as today - maybe they were slower. Whatever, the rate should not matter, its the actual temperature that is supposed to trigger the subsequent warmings, isn’t it?”

    You’re ignoring a lot of evidence that it’s currently warmer today than it has been in thousands of years, ice shelves and glaciers that have melted back and left behind biological evidence that can be carbon dated. Here’s a short list:

    - Western Canada tree stumps 7,000 years old;
    - Baffin island plants more than 1,500 years old;
    - The “ice man” found in the Alps, 5,000 years old;
    - The flowers left behind in the melt of South American glacires, 5,000 years old;
    - The Larsen ice shelf, 12,000 years old.

    In addition, there’s evidence that the Arctic Ocean hasn’t been ice-free for more than a million years. We’re going to see that in the next 5 to 25 years.

    And don’t forget that the CO2 forcing is continuing to increase, as we haven’t started to make a dent in the amount of our carbon emissions.

    There’s also about another 0.5 degrees C “in the pipeline” from the current forcing.

  • fred // April 6, 2008 at 7:00 am

    KF - the important thing is to figure out the logic of what’s being argued, then consider the evidence. It seems like the version of the argument implied by your comment would be: yes, feedbacks are always triggered by warmings, and had there been any warmings in the past comparable to the one we see today, they would have been triggered. But, your argument would go on, there have been none, so it was never triggered. If this is the argument, then it would be falsified by the discovery of one episode of previous warming which did not trigger the feedbacks.

    You argue that there have not been any comparable warmings in the last few thousand years. Not sure. Obviously the Middle Ages or Roman times is hard to establish with certainty. Though, the Romans did grow grapes for wine near Hadrian’s Wall, and Hannibal did cross the Alps, and the Vikings did farm in Greenland, none of which we could do now. Maybe it was regional. If this form of the argument is the generally accepted one, then MBH and similar proxy studies on the last 2000 years are absolutely central to the debate.

    But come further forwards. If you look at the charts for the early 20C, you’d have to ask why that warming was not enough to trigger the feedbacks. There could be an explanation, its just not clear what it is.

    [Response: You're laboring under some serious misconceptions, primarily because you've been suckered by propaganda. For instance, all the things you say "none of which we could do now," actually ARE happening now (except Hannibal crossing the alps, and it's Greenlanders rather than Vikings farming in Greenland).

    And the feedbacks DID happen during previous warmings. There's no "minimal level" of warming required to trigger feedbacks, they just happen. If the warming is small, so is the feedback, if it's large, the feedback follows suit.]

  • fred // April 6, 2008 at 7:03 am

    Just to add a bit to the previous comment: is there any quantification of the feedback effect? That is, is there any account which says how much initial warming is required to trigger it, and what the magnitude of the effect is at different initial warmings?

  • Gavin's Pussycat // April 6, 2008 at 12:33 pm

    Geoff Larsen,

    interesting stuff. Cloud cover is definitely the most uncertain element in our understanding of the climate system, and the thing to focus new work on.

    Taking note of the argument of the difficulty of correctly identifying cause and effect; doesn’t this also apply to the Spencer et al. (2007) paper? I remember reading it and thinking just that.

  • L Miller // April 6, 2008 at 2:41 pm

    Just to add a bit to the previous comment: is there any quantification of the feedback effect? That is, is there any account which says how much initial warming is required to trigger it, and what the magnitude of the effect is at different initial warmings?

    As Tamino already mentioned above there is no “minimum amount of warming needed to trigger feedback”. Climate is complex nonlinear feedback system with multiple inputs and outputs but you can get an idea of what feedback does by looking at a simple single input, single output linear feedback system. Lets say B is your feedback factor and A is your systems response without any feedback at all.

    http://upload.wikimedia.org/wikipedia/commons/e/ed/Ideal_feedback_model.svg

    In this case your response an input (forcing) will be:

    Negative feedback
    Change in output / change in input = A/(1 + B*A)

    Positive feedback
    Change in output / change in input = A/(1 - B*A)

    (Note: For the positive feedback loop to remain stable B*A must be small (between 0 < B < 1) but the negative loop will always be stable unless there is a time delay in the feedback factor B.)

    If A = 1 and B = 0.5 and you get a change in input (forcing) of 10%
    Negative feedback 0.1(1+ 0.5) = ~6.7% change in output

    Positive feedback 0.1((1-0.5) = ~20% change in output

    IOW positive feedback gives you changes in output that are greater then your forcing, negative feedback gives you changes in output that are smaller then your forcing. This is always going on and it’s contingent on “hitting a certain point for feedback to kick in”. In fact if you look at the small magnitude of the forcing thought to have caused previous climate changes you can’t explain it without significant positive feedback.

  • fred // April 6, 2008 at 3:19 pm

    I’m just trying to understand what the argument is at the moment. It is, then, that a given amount of forcing is amplified by a certain percentage?

    Tamino, if you would like to take a trip to Hadrian’s Wall one of these days, I will travel to you there. It is an interesting and remarkable historic monument. I am not sure of the evidence for vine growing there in Roman times, but can assure you, there are none there now. And if you asked the local inhabitants why not, you would get a colorful answer in what you might think was ancient Pictish!

    [Response: You're not sure what the evidence is? In your previous comment you simply stated it as a fact. And you used the phrase "near Hadrian's wall," which could be interpreted as covering a large area of England.

    It sounds a whole lot like the "can't grow wine grapes in modern England" argument from Avery & Singer's idiotic book. You might be interested in this.]

  • L Miller // April 6, 2008 at 5:02 pm

    I’m just trying to understand what the argument is at the moment. It is, then, that a given amount of forcing is amplified by a certain percentage?

    Because climate isn’t a linear system it won’t be a fixed percentage but otherwise that’s the basic idea. There are some other effects like response time and some desirable properties like being able to eliminate the effect of an unstable element.

    This isn’t “an argument” though; it’s just what feedback does. Feedback is an element that plays a large part in determining the final response of a system. When feedback exists in a system you are never going to be able to understand that how that system responds to a forcing without accounting for that feedback, that’s not so much an argument as a fact.

  • Gavin's Pussycat // April 6, 2008 at 6:52 pm

    Stupid question: in the above feedback graph from Bony et al (2007), does the vertical axis give the initial feedback f? Or rather, the total feedback f+f2+f3+… ? Also, it is not a dimensionless number as f etc. would be… shouldn’t these values be multiplied by some sensitivity value in units of K/(W/m2)?

    (BTW the unit stated in the caption appears to be wrong :-) )

    [Response: Not a stupid question at all. As I see it, it's the initial feedback not the total. And yes, to transform that to dimensionless feedback parameter one should multiply by the 0.3 K/(W/m^2) "default" sensitivity. Finally, I agree the units should be W/m^2/K, not W/m/K; I expect it's just a typo.]

  • TCO // April 6, 2008 at 7:58 pm

    The Clausius Clapeyron equation of thermodynamics does not dictate constant relative humidity. I do agree that warming will tend to raise H2O in the atmosphere, but it is Le Chatelier’s principle really. It is NOT CLausius Clapeyron (which does not dictate mixtures of states in any case).

  • TCO // April 6, 2008 at 8:09 pm

    1. Very nice post.

    2. I think there are interesting analogies in reactor design and in physical intution for how various factors (shape, age, temp) etc affect various aspecst of nuclear reactor (power, Centerline temp, xenon, temp coeffe of reactivity, etc.) I wonder if anyone has remarked on this and/or drawn some insights between the fields.

    3. I think the reason for the high spread in feedback estimates is that the system is very complex and hard to properly model. In some sense that might mean we’re more at risk, but it also means that we do’t know for sure that we are seriously at risk.

    4. Given the imho serious issues with undersanding this complex system, I fall back on the observed runup in temp with CO2 as one of the best indicators of the reality of AGW and the danger of future AGW.

  • henrikoelund // April 6, 2008 at 10:13 pm

    Tamino
    You say that Greenlanders are now farming again in Greenland? Please tell me where - I have been to Greenland several times - the only farming I have seen are the old Viking farms, still buried in permafrost.

    [Response: Look here.

    Maybe I need a new policy. Folks who aren't willing to spend five minutes with google, have their comments disappear without explanation.]

  • Hank Roberts // April 6, 2008 at 11:19 pm

    You could include an explanation:
    http://justfuckinggoogleit.com/

  • steven mosher // April 7, 2008 at 12:24 am

    Dang Tamino, are you testy cause it’s tax season? I know I was for the past few days.

    Let me suggest something and then you throw mud pies or not.

    1. Just snip the idiot stuff that bugs you. The stuff that goes over whatever line you determine. people will figure out the line. Part of the fun of posting is testing that line. So just snip stuff. people will get pissed, the smart ones will discern your limits. Don’t be capricious and people will regulate their own behavior ( except for TCO, he requires regular beatings )

    2. Don’t reply inline to the idiot stuff that bugs you. Dont tell an idiot that they are an idiot.
    Unless of course I am that idiot. Knowledge is power. ‘yes dear’ is the right response or just dont feed the trolls.

    3. If you must feed a troll, then stuff them full. Everybody jump on the troll. This destroys the discussion, but it’s often fun.

    [Response: What's "part of the fun" for the kids, is a real chore for the one who has to clean up after dozens of them.]

  • Ken Feldman // April 7, 2008 at 5:09 am

    I’m curious as to why skeptics argue that Hannibal’s route across the Alps couldn’t be done today. Although the pass he took isn’t known, it’s known that he crossed in the snow and his troops were dispirited and tired after marching through the snow for two days. See this link:

    http://www.livius.org/ha-hd/hannibal/alps.html

    As to farming in Greenland, you have to ignore a lot of stories to be unaware of how much of it is occuring now. This is a good summary:

    http://www.csmonitor.com/2007/1001/p01s02-wogn.html

  • fred // April 7, 2008 at 6:37 am

    The Hadrian’s Wall wine reference was from a usually reliable friend, but I have not been able to verify it.

    Northampton and Leeds seem to be the furthest north confirmed sites. Not Hadrian’s Wall, but further north than you’d think of trying it today. English wine definitely does exist today, I’ve drunk some from a Sussex vineyard. It wasn’t more than acceptable, but it was English, and apparently there are quite a few (small scale) vineyards springing up in southern England. I’m surprised to hear anyone denies that.

    However, the question remains - not rhetorical but just getting clear about the argument. The argument is that any warming will be subject to the feedback amplification. There undoubtedly have been warmings in the past 2000 years. There undoubtedly was a Roman and a Medieval warming. We can argue about how great they were later. They did not lead to about a 0.2 degree warming per decade as forecast by the IPCC. Are we saying that the only reason they did not was because they were not big enough warmings?

    The question is then not so much whether farming in Greenland or vineyards in the UK are possible today. The question is why the previous warmings which allowed them in the past did not invoke the feedback consequences that are forecast for this century.

  • fred // April 7, 2008 at 7:21 am

    I can think of three reasons why the feedbacks might not have happened during previous warmings:

    1) The temperature impulse was a one-off and short lived, today’s is hypothesized to be continuous and long duration. We’d need some mathematics to make this plausible as explanation.

    2) The previous initial non-CO2 warming wasn’t big enough. Again, some math needed: how big must it be to start the cycle?

    3) It was regional - the warmings did occur, but not globally, so large ocean outgassings did not happen because it didn’t get warm enough where it counts.

    4) There have been no previous warmings on the present scale in historical times. This is what the Hockey Stick seemed to show.

    Maybe more possibilities will occur to others.

  • Geoff Larsen // April 7, 2008 at 11:13 am

    Gavin’s Pussycat

    “Taking note of the argument of the difficulty of correctly identifying cause and effect; doesn’t this also apply to the Spencer et al. (2007) paper? I remember reading it and thinking just that”.

    I don’t see how unless I’m misreading; this paper relates to satellite observations of dynamic, daily oscillations of a precipitation system.

    First of all one should discriminate between the effect on warming/cooling of low-level clouds(eg cumulus clouds) & high-altitude clouds (eg cirri-form (ice) clouds in the middle & upper tropical troposphere). The former cool & the latter warm.

    Spencer et al’s Aug. 2007 paper, “Cloud and radiation budget changes associated with tropical intraseasonal oscillations”, relates to the latter, warming type of clouds.

    Their conclusions were: -

    “The composite of fifteen strong intraseasonal oscillations we examined revealed that enhanced radiative cooling of the ocean-atmosphere system occurs during the
    tropospheric warm phase of the oscillation. Our measured sensitivity of total (SW + LW) cloud radiative forcing to tropospheric temperature is _6.1 W m_2 K_1. During the composite oscillation’s rainy, tropospheric warming phase,
    the long-wave flux anomalies unexpectedly transitioned from warming to cooling, behavior which was traced to a decrease in ice cloud coverage. This decrease in ice cloud coverage is nominally supportive of Lindzen’s ‘‘infrared
    iris’’ hypothesis. While the time scales addressed here are short and not necessarily indicative of climate time scales, it must be remembered that all moist convective adjustment occurs on short time scales. Since these intraseasonal
    oscillations represent a dominant mode of convective variability in the tropical
    troposphere, their behavior should be
    considered when testing the convective and cloud parameterizations in climate models that are used to predict global warming”.

  • Hansen's Bulldog // April 7, 2008 at 12:25 pm

    The reason we’re expecting such rapid warming this century is that the change in forcing is so fast. Just to give an idea of the time scales: during a deglaciation, CO2 concentration will rise by about 100 ppmv (which for a deglaciation is a feedback, not a forcing). But that takes 5,000 years minimum. We’ve managed to do it in about 200 years — 25 times as fast — and since the increased CO2 is anthropogenic, it’s a forcing not a feedback.

    And fred, your impression that medieval/Roman warming might have been as great as we have today, is no more founded on solid evidence than the claims that they still can’t farm in Greenland or grow wine grapes in England.

  • Henry // April 7, 2008 at 12:46 pm

    Tamino, what would explain the possible levelling/reduction of year on year CO2 which looks as though it might be recorded at Mauna Loa this year?

  • Timothy Chase // April 7, 2008 at 1:59 pm

    Geoff Larsen wrote:

    Spencer et al’s Aug. 2007 paper, “Cloud and radiation budget changes associated with tropical intraseasonal oscillations”, relates to the latter, warming type of clouds.

    Their conclusions were: …

    Spencer is studying the Madden-Julian Oscillation as a means of determining the effects of higher temperatures upon cloud formation over the ocean. But there is only one problem: as this is an oscillation, what you are dealing with is periodic behavior which by its very nature dynamic, not static, yet you are trying to draw conclusions about what will essentially be static from it - what happens when the higher sea surface temperature forces the system to equilibrium - and the clouds that are associated with that equilibrium.

    To see the problem with this, imagine trying to calculate the relationship between the climate’s sensitivity to solar insolation - on the basis of the difference in temperature between day and night. Obviously you can’t draw a conclusion regarding the temperature that the earth would be if days were as dark as nights simply on the basis of how cold the nights are - because nights haven’t had the chance to achieve equilibrium.

  • fred // April 7, 2008 at 3:36 pm

    Tamino, maybe Roman & Medieval warmings were not as great as today’s.

    But if they were, does the theory require them to have produced the levels of warming forecast from today’s warming?

    In short are you arguing for number 4 of my three choices above? I’m not arguing is it right or wrong, just want to know what the theory is.

    [Response: I'd say that if those warmings were as warm as today, but that the response already included the feedbacks, then there'd be no further warming expected. Since the time scale for equilibrium is about 30 years (according to computer models), we can expect that the feedback effect would already have been felt (aside: James Hansen has raised the possibility of "fast" and "slow" feedbacks, the fast corresponding to about 30 years, the slow taking longer). If the warming due to *forcing* were as great as we see today, then I'd fully expect feedbacks to bring about even more.

    And one of the things to keep in mind is that forecasts for the next century don't just include feedback response to what we've already done, they include the expectation that we'll do more. Just about everybody (myself included) expects CO2 levels to continue to rise over the next several decades due to human activity, possible longer depending on how quickly and effectively we reduce greenhouse gas emissions. Computer models suggest that if we halt greenhouse gas emissions completely, right now, we'll only get about another 0.6 deg.C warming *total*.

    And yes, my belief is that it's #4 that applies. I might modify it to say that there have been no previous forcing changes on the modern scale in historical times, and earth hasn't yet equilibrated to the forcing change.]

  • David B. Benson // April 7, 2008 at 5:51 pm

    fred — I know of no evidence that in Roman times the globe was warmer than today and plenty of evidence which suggests it was not. Just because Roman Britian was warmer does not mean the entire world was.

    The same applies to the midieval warm period. There is good evidence which suggests it was only warm in parts of northern Europe, and not globally.

  • Lee // April 7, 2008 at 6:47 pm

    **if* Roman Britain was even warmer.

    The current northern limit of grape cultivation in England is actually very near Hadrian’s wall. Check out the limit on this map, and the commercial wineries in the “Northern” region by clicking the link.

    http://www.stratsplace.com/maps/england.html

  • P. Lewis // April 7, 2008 at 7:26 pm

    I wasn’t going to enter into this, but since Lee has ventured, I’ll just to add the following.

    The most northerly “commercial” vineyard in the UK (below the line in Lee’s linked map) is Mount Pleasant Vineyard, at Bolton Le Sands, near Carnforth, just south of the Lake District.

    This is only slightly further north than Ryedale Vineyards, at Westow, about 20 km NW of York, who have been going about 20 years.

    There are also limited vineyards at Helmsley and Castle Bolton (about midway between the two above), which I’ve visited in the last couple of years.

    None of these is actually commercial with regard to wine production. Ryedale Vineyards, weather permitting, may be productive with regard to wine this year or next I think (they’ve been going about 20 years growing vines). Mount Pleasant Vineyard has been growing vines since 1996 and AFAIK are not producing wine (of even small commercial quantities — but if they’re looking in …).

    And there are anecdotal instances (letters) of small numbers of vines being grown outdoors in Scotland above, but close to, the line drawn in Lee’s linked map, though this is essentially just gardening so far as I’m aware — and likely only in western Scotland around the Argyll area, which is subject to generally warmer weather than the rest of Scotland by virtue of the impact of the North Atlantic Current of the Gulf Stream.

  • Hank Roberts // April 7, 2008 at 7:58 pm

    Henry, look at the text on preliminary vs. final data alongside the Mauna Loa chart, and look back at previous years for similar variations even after final numbers were charted. Nothing out of the ordinary has showed up.

    You may also want to compare the change around the time the USSR collapsed with the next few years, depending on what the auditors make of the current global economy.

  • Henry // April 7, 2008 at 8:19 pm

    That’s helpful, thanks Hank. So in your view there’s nothing unusual going to happen with the CO2 figures? You don’t see them ever levelling off or even decreasing on their own?

  • fred // April 7, 2008 at 8:38 pm

    http://www.winelandsofbritain.co.uk/lecture.htm

    has a map by the author of the book Winelands of Britain. If this is right, then I was wrong about vineyards near Hadrian’s Wall in Roman times, and Leeds is probably also over the border. The map does seem to show that today’s northerly limit is roughly comparable to the medieval and Roman limits.

    Still, its not that critical to our particular argument if it was a bit warmer or cooler, what counts is was it reasonably close.

    Northampton turns out to be not all that far north - its within both the modern and ancient limits, so I was wrong to say you wouldn’t go that far north today. There were reports in the Independent that the Nene Valley (near there) had been quite a wine center in Roman times.

    Richard Selley, the author, also shows on the map where wine will be grown in future. Hadrian’s Wall does appear feasible according to this, but not until 2100. They will probably still talk Pictish then….

  • Hank Roberts // April 7, 2008 at 9:08 pm

    > So in your view there’s nothing
    > unusual going to happen going to
    > happen

    Er, no. I said nothing of the sort.

    I recommend reading what’s published. I will recommend that you read it again later, to see if anything unusual happened.

    Look at the trend. Look at what the source says about preliminary information and how long it takes to have final information available.

    Look at what you want to see, and avoid seeing what isn’t there.

  • Hank Roberts // April 7, 2008 at 9:11 pm

    Oh, and, Henry, you might take a look at this image too.

    http://tamino.files.wordpress.com/2008/04/data.jpg?w=500

    See anything that resembles ” levelling off or even decreasing on their own” there?

    If so reading the accompanying article will be helpful.

  • TCO // April 7, 2008 at 11:07 pm

    (Actually trying to chat science while drinking gin)

    For sake of discussion:* Let’s accept that the MWP was confined to Northern Europe. Let’s further accept that within that region that it had reasonable duration/magnitude such that definite affects (treeline moves, etc) were similar and slightly in excess of to date warming in Northern Europe.

    Now given the above: what does this mean about the system? Is it like a squishy balloon that is prone to oscillation in location of warmness but not different global averages? Do models of the climate indicate that it is prone to this sort of behavior? Was it some sort of long term cycle in mechanism of currents or the like? Or just the succession of excursions (throwing a bunch of sixes)? If the system is capable of this sort of definite deviation from averageness, does it make it more likely that the system is capable of overall devations?

    *Within this talk, you can’t then argue against these premises. The whole point is to discuss what it means if they are true. Not to debate if they are. (That can occur on it’s own.)

  • David B. Benson // April 8, 2008 at 12:37 am

    TCO // April 7, 2008 at 11:07 pm — I think that MWP also included some portions of eastern North America, Greenland and Iceland. But it does not change what I take is your central point.

    The Gulf Stream takes warm salty water from the Caribbean (or thereabouts) to northern Europe. Which keeps northern Europe warmer when it does and cooler when it doesn’t. Just where the water cools enough to sink into the deep ocean then ‘depends’. But I doubt this can be considered to be a long-term cycle. It is not like a harmonic oscillator.

    We know from paleoclimate studies that the climate can swing about 6 K between stades (massive ice sheets) and interglacials. Within that range there is considerable climate internal variability.

  • TCO // April 8, 2008 at 1:25 am

    I have questions, more than I have points. Sometimes, the questions are pointed, but they really still are questions. People get too wrapped around their fragile egos and don’t want to really think and enjoy the beauty of discovering math and nature and our own capacity for discovery.

    On the ice ages, let’s leave them out for the second as they may be explained by orbital changes.

  • L Miller // April 8, 2008 at 4:45 am

    On the ice ages, let’s leave them out for the second as they may be explained by orbital changes.

    The point is that ice ages can’t be explained by orbital changes themselves because they have almost no effect on the total solar energy the earth receives. This means without feedback they can’t cause ice ages.

    What causes ice ages is how much solar energy goes into the Northern Hemisphere. When a larger percentage of the solar energy the earth receives goes to the NH the whole planet warms, when the SH gets more the whole planet cools. The total solar energy the earth receives stays pretty much constant.

  • fred // April 8, 2008 at 6:05 am

    Tamino gives a logically coherent answer to the MWP and RWP question. The point is that even if the temps are similar to today’s, they are arguably not comparable, because of the length of time it takes the feedbacks to kick in. So what we would be comparing is the MWP at its height with the modern warming at its start.

    Its essentially saying that it may be warmer now than it was then in like for like terms, even if the temperatures of 2008 were roughly similar to those of 1208. This additional ‘warmth’ would then be enough to permit us to forecast, using the same feedback mechanism, that feedbacks would lead to a larger ultimate rise in temperature this century.

    Interesting point that needs some thought. Hansen’s recent paper seems to be along the same lines with the long term and near term feedbacks, and seems to be suggesting a sensitivity of the climate to CO2 doubling of around 6C.

    If its right, its quite important, and its worth a thread in its own right.

    [Response: In fact RealClimate has a post on that right now. From which I learned a few things; for instance I mistakenly included ice albedo as one element of sensitivity estimates, but ice sheet dynamics are not so included (although snow albedo is); ice sheets fall into the "slow" rather than "fast" category.

    I'll emphasize again that the real reason we're expecting so much temperature increase over the next century is that we expect so much increase in forcing (because of continued GHG emissions); if we could magically halt all emissions instantly we're only headed for about another 0.6 deg.C. We haven't doubled CO2 from pre-industrial levels yet! But -- emissions aren't gonna hit zero any time soon.]

  • Petro // April 8, 2008 at 1:06 pm

    Tamino repeated:

    “..we’re only headed for about another 0.6 deg.C.”

    Even that would be about the same amount of increase in the global temp we have felt during last century. And that will come only in a third of the time.

    We human have already induced a dramatic climate change. Our era is not named as anthropocene in vain.

  • TCO // April 8, 2008 at 1:26 pm

    L Miller:

    Agreed and I knew that.

  • luminous beauty // April 8, 2008 at 1:59 pm

    TCO,

    You might be amused to discover that the really interesting outcome of MBH PCA is that regional climate variability is mapped and delineated.

    The kind of thing that gets lost and confused when one is too busy with the trees to see the forest.

  • TCO // April 8, 2008 at 9:37 pm

    I’m aware that there is a part of his paper that looks into this, but I’ve never looked much into it, nor do I have an opinion as to the credibility (or even importance) of this section.

  • fred // April 8, 2008 at 10:32 pm

    Christopher Monckton has a guest post on Roger Pielke’s site, on feedbacks and their magnitude and changing estimates of them. Worth reading.

    No, you are quite right on emissions. There is no way China India and Russia are going to cut back on emissions in the least, any more than the Japanese will ever give up on whaling while there is still even one of those magnificent creatures left alive. It makes you think Freud was right about Thanatos. Or Calvin about original sin. Or both.

    [Response: Christopher Monckton IS a [edit].]

  • luminous beauty // April 8, 2008 at 10:34 pm

    Thus I surmised.

  • Hansen's Bulldog // April 8, 2008 at 11:04 pm

    fred, you need to learn that sometimes the word “[edit]” really does apply. Some people *really do* fit that description; you don’t, but Anthony Watts, and Christopher Monckton too, absolutely definitely do.

    You need to be able to tell the skeptics from the [edit]. When you recommend anything by Monckton, you show that you don’t know how. You repeat claims that we can’t farm in Greenland or grow wine grapes near Hadrian’s wall — did those beliefs advance your understanding, or did they obstruct it? You got that information from [edit].

    So accept the ugly truth: they really exist. Calling them by polite names doesn’t alter the fact that not only will they fail to advance your understanding, they’ll actually retard it. It’s quite clear that your goal is to understand the truth. Until you learn who the real [edit] are and clear them out of the way, you won’t be able to achieve your goal.

  • David B. Benson // April 8, 2008 at 11:30 pm

    TCO // April 7, 2008 at 11:07 pm — With regard to your questions about MWP, etc., have you considered W.F. Ruddiman’s thesis about the Holocene, as set forth in his popular book “Plows, Plagues and Petroleum”?

    There is even a Wikipedia page about it…

  • TCO // April 8, 2008 at 11:37 pm

    Here is what I got when I googled “Peilke Monkton feedback”:

    http://sciencepolicy.colorado.edu/prometheus/archives/prediction_and_forecasting/001343the_consistentwith_.html

    I find the discussion interesting and the questions that the skeptic is raising interesting. And untardish. And I didn’t see Monkton around.

  • TCO // April 8, 2008 at 11:54 pm

    Benson: I just looked at a bunch of the Ruddiman stuff. Not sure what your point is or how that stuff ties in.

  • dhogaza // April 9, 2008 at 12:04 am

    TCO, there are two Roger Pielke’s, The Younger (who is probably too rational to allow a [edit] like Monckton to post a guest blog entry at prometheus), and The Elder, who is more than willing to allow a [edit] like Monckton on board.

    Here: http://climatesci.org/

  • dhogaza // April 9, 2008 at 12:05 am

    strange, it ate my post?

    Anyway, TCO, you want to visit the website of Pielke The Irrational Elder, not Pielke The More Rational Younger.

    http://climatesci.org/

    Now let’s see if my post appears awaiting moderation this time …

  • dhogaza // April 9, 2008 at 12:06 am

    Third try?

    TCO, try Pielke Sr’s site, climatesci.org.

  • David B. Benson // April 9, 2008 at 12:56 am

    TCO // April 8, 2008 at 11:54 pm — Ruddiman proposes that the MWP was anthropogenic in origin as was the so-called Little Ice Age. He claims the unusual stability of the Holocene climate was directly due to human activity.

  • henrikoelund // April 9, 2008 at 1:11 am

    Tamino - thanks for the link. And Ken Feldman too.
    You said:
    “Maybe I need a new policy. Folks who aren’t willing to spend five minutes with google, have their comments disappear without explanation.”

    Well it´s your blog.

    Did you really read Der Spiegel? The guys farming are not all Greenlanders - one Dane, one Swede and an Inuit - the Swede hoping to strike gold(Vanadium) - spoken like a true farmer!
    And what did they harvest? - oh yeah, potatoes the most resilient vegetable of them all. And he had reindeer - one of the most resilient animals in the world.
    And then there were 19 (nineteen) cows on the entire island - are you serious? 19 cows! This is farming!
    This is priceless stuff. I have to believe this is a joke on your part - and a good one!
    The other story from Qassiarsuk was also nice, more potatoes and even radishes. Unfortunately the sheep did not have anything to eat. Strange with all this green in the pictures. Notice the ice is still in the water in summer.
    The article mentioned that Eric the Red had hundreds of cows - and he did not have choppers to fly in hay. Could it be that it was warmer then? - so there was enough grass to eat.
    Being Danish myself we hear a lot about the weather in Greenland. This winter it was all about record low temps down to -40 C in Nuuk, the capital in the south of Greenland and of course the ice. To this day in April + 90 % of the coastline is covered with ice. Not exactly like Northern Europe.
    I hope all the cows made it through this climate change.

    [Response: First you directly implied that there's no farming at all happening in Greenland. Now that that's been shown false, you want to suggest that they're "only" growing potatoes, as if that doesn't count. Keep moving that goalpost.

    There are more web references about agriculture in Greenland. I'll let you get familiar with google on your won.]

  • TCO // April 9, 2008 at 1:34 am

    Dhog:

    Ok, I looked at that. It was somewhat [edit]. Not as wierd as the Basil stuff, but I didn’t really follow it that well actually. The feedback stuff seemed to be presented in a reasonable manner (even if wrong…or right…I did not parse it.) At the end, there were a couple of those trademark meanders, sniping at other things (adaption versus mitigation, and the recent down trend). I find this to be a common flaw of skeptics (SM). At the least it is sloppy and annoying. At the worst, it shows a sort of skewed brain.

  • TCO // April 9, 2008 at 1:36 am

    Benson:

    I guess I need to read the Ruddiman stuff more closely. I realize that he thinks the agricultural revolution has had an impact, but was not aware that he had a theory describing why the MWP was so prominent than and not for the last several hundred years (i.e. the wiggliness).

  • Dano // April 9, 2008 at 2:18 am

    First, apologies for the edited phrase. At one time I knew better. Now,

    Speaking of human nature and confirmation bias, that Monckton on RP Sr’s site is a good example of how human nature and confirmation bias works, and the denial industry takes full advantage of it:

    This is not a typical denialist article that uses the construction of agreement-argument-message.

    Agreement must be first - as in sales - in order to get the subject’s head nodding. Then the cherry-picked/out-of-context/quote-mined etc argument, then the message that the author wishes to deliver. Why? It is key in sales to get the subject’s head nodding to have success. This is why you see so many denialist industry articles with little anecdotes in the first 2 paras of the work. In the future, look at these constructs when reading something from the denial industry. You’ll see it.

    Now, why is the Monckton a poor piece of propaganda?

    First, there is the distraction of many equations. They are very attractive and authoritative, hence their placement first - to impress the lay reader. But the lay reader won’t be shaking their head in agreement.

    Next, there is the appearance in the last 2 paras of the trigger phrases:

    o expensive guesswork
    o “global warming.” [scare quotes is a current message -D]
    o the self-evident truth that adaptation as (and if) necessary would be orders of magnitude more cost-effective than mitigation
    o the IPCC’s bizarre decision
    o IPCC’s estimates of climate sensitivity are prodigiously exaggerated
    o temperatures have not risen for a decade
    o the phase-transition in global temperature trends that occurred in late 2001 [watch for this phrase - will it catch, or is this message too poorly constructed to catch on -D]
    o there is no “climate crisis”

    Remember - repetition is the key to successful messaging. Monckton got that training. These will reinforce the standard message. But,

    The central message - no great reliance can be placed upon the IPCC’s central estimates - is buried deep in the confusion of equations and is partially lost. It is partially recovered with the cherry-picked graph and the implication of the caption “the rate of warming is self-evidently less than that which the IPCC had expected, and is very likely to be harmless. ”

    I suspect the caption is expected to be the message carried forth in this cycle by unsuspecting dupes, rubes, stooges, bots, and denialists.

    Lastly, if anyone had the tiniest doubt over whether RP Sr was a denialist, this Monckton piece should put that to rest. Wow. What a pile, in so many ways.

    Best,

    D

  • TCO // April 9, 2008 at 2:39 am

    Actually I felt that Sr. had some reservations as he made it clear that the post was from someone else and that peer-reviewed literature needed to be done if the result really had any worth.

  • Hank Roberts // April 9, 2008 at 2:56 am

    >Monckton

    Consider this is business advertising and it makes sense.

    http://members.ebay.co.uk/ws/eBayISAPI.dll?ViewUserPage&userid=bikerbikerbiker
    Christopher Monckton Limited, business consultants

    Europe’s leading business consultancy, specialising in solving problems caused by over-mighty State bureaucracy so that your business can survive and be profitable. We deal firmly with tax offices, zoning and planning authorities, major departments of government, and international governmental organizations. If the State is treating your business unfairly, call us on +44 7974 431410 or email monckton@mail.com. We’re here to help.
    The above page is maintained by: bikerbikerbiker( 60Feedback score is 50 to 99) About Me

  • Lee // April 9, 2008 at 3:53 am

    Greenland has grass / hay farming for sheep, with close to 25,000 sheep slaughtered annually in recent years. In 2007, there were reports that some farms managed two hay cuttings for the first time. Greenland has emerging dairy farming, with a target of 100,000 liters of milk annually within a couple years. They are growing potatoes, carrots, and in 2007 for the first time ever, broccoli, along with salad farms of several new vegetables. This is all a result of longer growing season, and more land amenable to farming.

    Citations for this are all over the internet - Google is your friend. Or maybe not. These data were from memory from the last time I encountered someone claiming that there is no farming on Greenland.

  • dhogaza // April 9, 2008 at 4:16 am

    Actually I felt that Sr. had some reservations as he made it clear that the post was from someone else and that peer-reviewed literature needed to be done if the result really had any worth.

    Dude, Faux-Lord Monckton is a well-known crank, and there’s no way in the world that Sr. is unaware of it.

    Allowing to appear, even with almost unnoticeable caveats, is an endorsement, and is in line with Sr’s beliefs.

    You reach too hard to support your own beliefs by arguing for the innocence of those who don’t deserve the defense…

  • Timothy Chase // April 9, 2008 at 4:19 am

    henrikoelund wrote:

    And what did they harvest? - oh yeah, potatoes the most resilient vegetable of them all. And he had reindeer - one of the most resilient animals in the world…

    Not just potatos…

    Greenland’s broccoli is bad for our health
    By SARAH LYALLIN
    NARSARSUAQ, GREENLAND
    04 November 2007
    http://news.scotsman.com/climatechange/Greenlands-broccoli-is-bad-for.3477050.jp

    Incidentally, it pays to keep in mind that when we are speaking of broccoli, cauliflower, or carrots, these are veggies that have to compete with what can be imported by means of modern transportation — and they are still cheaper for people in Greenland to grow for themselves. Strawberries on the otherhand are still more expensive to grow locally. The same — it would appear — is true of potatos — which can be grown abroad and shipped in more cheaply than it can be locally grown. But centuries ago, the choice wouldn’t have been between what could be produced locally and that which can be shipped in but between producing locally or not having any produce at all.

    Not arguing that Greenland wasn’t warmer a few centuries ago than it is today. That is quite possible — and in fact I suspect it was.

    However, the current view is that any Medieval Warm Period was regional, not global, that the global average temperature hasn’t been as high as this for several thousand years — and that temperatures will continue to climb for several decades even if we stop emissions today. And while the justification for various conclusions in paleoclimatology may ebb and flow to some extent with the accumulation of empirical evidence, I believe radiation transfer theory is fairly solid — as it rests upon quantum mechanics. More carbon dioxide necessarily means that the atmosphere will become more opaque to thermal radiation, and the degree to which it does this is as much a given as the rate at which a rock will fall when released.

  • fred // April 9, 2008 at 6:30 am

    You all need to stop frothing at the mouth and get to the part that is interesting. If it is correct. That is the part in green and pink a bit down the page, where he states how the estimates for forcing and feedback have changed over time. I don’t know if its true, but if it is, its interesting.

    Hank R, what on earth is that link about?

  • fred // April 9, 2008 at 6:45 am

    Pielke doesn’t seem in the least irrational. It may not be a site, and he may not be a person, who you all agree with. But he’s perfectly rational. It may be mistaken to think that AGW proponents have given too much emphasis to CO2 as opposed to other man made changes. It may be quite wrong to think that the heat content of the oceans is a significant indicator. But it is not irrational. If you put everyone who has such reasonable, but perhaps mistaken, ideas into the category of denialists, you really are treating this thing like a religion and calling everyone who differs from you in any respect an unbeliever. In an open society you will produce more skeptics than converts by doing that.

    I don’t really see why he should not have given Monckton a guest post, or what is so terrible about the posting. The temp graph seems a bit funny, but I’m not sure why the hysterics about the rest of the post. Other than that you don’t like Monckton. Well, tough, deal with the arguments.

  • Hansen's Bulldog // April 9, 2008 at 12:49 pm

    fred, I’m actually trying to help you achieve your goal.

    So here’s a serious question: do you agree that giving serious consideration to Anthony Watts’ blog posts moves you *farther* from the truth rather than closer? Or would you say that Watts has an interesting post about feedbacks, and if I retort that he’s not worth listening to, you’d respond “Well, tough, deal with the arguments.”

    Here’s another serious question: *if* you accept Watts as unreliable and not worth responding to, do you think he’s the only one?

    I did this topic at your request. But the request was rather a long time ago. Along the way I got seriously sidetracked by a number of things, including refutations of idiotic arguments. How much time and effort did I expend, how long did you have to wait for the topic to be discussed seriously? Frankly, I’m really looking forward to forgetting about Watts. Let him go his merry way in delusion, I have better things to do.

    Christopher Monckton is in the same class with Watts. You say “Well, tough, deal with the arguments.” I have better things to do. Now here is the most important lesson you may ever learn about the global warming “debate”: YOU TOO HAVE BETTER THINGS TO DO.

    Until you accept the fact that some delusionists aren’t worth listening to and don’t deserve the time it takes to respond, you yourself will cripple your understanding. Christopher Monckton is one of those: not worth reading or responding to. If you want to learn the truth, stop reading Monckton and become a regular at RealClimate.

  • Hank Roberts // April 9, 2008 at 7:41 pm

    > that link
    That’s Monckton’s business link.
    Check it out for yourself.

  • fred // April 9, 2008 at 7:55 pm

    Hank R, are you seriously saying that Christopher is selling his consulting services on ebay under the name of bikerbikerbiker?

    Seriously? The site itself is rather bare of clues as to who owns it. Maybe you know more?

  • Hank Roberts // April 9, 2008 at 8:17 pm

    Follow the links, Fred. It’s no secret.
    Google is your friend.

  • Adam // April 9, 2008 at 9:21 pm

    That phone number is also a mobile (cell) number (starts with a 7). Read into that what you will.

  • Hank Roberts // April 9, 2008 at 9:41 pm

    Clue:
    http://www.google.com/search?q=monckton+bikerbikerbiker

  • Tom Woods // April 10, 2008 at 12:58 am

    Tamino,

    Maybe I’m being ignorant here. But one step I never see included in feedbacks in papers I have read (especially when trying to determine how temperature changes from ice age to hypsythermal) is the sea-level change aspect. The average lapse rate in the troposphere is roughly 6.5°C/km. The sea-levels rose ~130m from the peak of the previous ice age to present. This would equate to a temperature rise of ~.8°C over land areas, would it not?

    If you have any information on this, perhaps a paper you could point me to that takes this into effect?

  • Timothy Chase // April 10, 2008 at 2:47 am

    Regarding Christopher Monkton’s now defunct consultancy, also check:

    http:// cei. org /content/christopher-monckton

    … but remove the spaces.

  • Hank Roberts // April 10, 2008 at 5:14 am

    CEI says he’s no longer a Director, but it’s not clear the business is closed. But someone else can worry about why he’s still advertising if he’s not doing it.

  • fred // April 10, 2008 at 5:31 am

    Well, he is a famous eccentric, and you could call that eccentric all right. Wonder if it generates any business? Perhaps I should try it.

    But getting back to the point, is his diagram about the changing relative importance assigned to direct forcing and feedback correct? Because without being very clear about what exactly it means, it is an interesting observation if true.

  • Barton Paul Levenson // April 10, 2008 at 10:23 pm

    fred posts:

    I don’t really see why he should not have given Monckton a guest post

    This is why:

    http://members.aol.com/bpl1960/Monckton.html

  • Barton Paul Levenson // April 10, 2008 at 10:25 pm

    Tom, your question interests me as well. Does anybody here know the answer?

  • Hank Roberts // April 11, 2008 at 1:36 am

    Gore’s added the newer research to his slide show — one slide remains from the old set: http://www.ted.com/talks/view/id/243

  • Lost and Confused // April 11, 2008 at 4:07 am

    I try not to be cynical, but the part of Al Gore’s presentation (that Hank Roberts linked) that stuck with me after watching that was his dishonesty about Daniel’s Harbour. In a part discussing the Arctic Circle, he shows a house falling off a cliff, as the cliff collapsed.

    The first thing to note is Daniel’s Harbour is nowhere near the Arctic Circle. The second thing to note, is the collapse was caused by erosion, a natural occurrence, not global warming.

    I would like to assume this is a honest mistake. I would also like to assume Gore will fix it, perhaps even admit to the mistake and apologize for it. Unfortunately, I find assuming things is difficult to do, and after the uncorrected errors in An Inconvenient Truth, I cannot assume this.

    The worst part is this kind of error is mostly meaningless. There is no reason for it not to be corrected. I hope that it is, but until it is, it will just be one more reason for me to scoff at Gore.

    [Response: I've heard, and I believe it to be true, that the erosion itself is due to the disappearance of sea ice and the melting of permafrost. Therefore it is indeed due to global warming.

    In my experience, the errors and outright lies in claims about mistakes in Gore's presentations, are vastly more numerous and more serious than mistakes in Gore's presentations. He's been the target of the worst "swift-boating" in modern times.]

  • fred // April 11, 2008 at 7:35 am

    Hank R, read your piece on Monckton. Still do not understand why any of this is a reason why Pielke should not give him a spot for this particular post.

    Still do not grasp why the movement in IPCC estimates on the relative contributions of feedback and direct forecasting cited in the post is either wrong or uninteresting.

    Your own views on MWP and what Wegman said differ from my own (if the committees were endorsement, I’d hate to see condemnation), but you’d still get a guest post. One of the nice things about Pielke is, he cites material on a variety of subjects from different points of view (as with the Willis stuff recently). It is hard to see why he should not. If Monckton’s post really is as awful as people are saying, though they do not say what about it is so awful, Pielke will have turned out to do his arguments no favors by publicizing them. They will just get refuted faster, and that will be good for us all.

  • dhogaza // April 11, 2008 at 1:14 pm

    Still do not understand why any of this is a reason why Pielke should not give him a spot for this particular post.

    Actually, I’m glad Pielke, Sr. did so. His reputation within the scientific community is already fairly well set, this just adds to it.

    Pielke Sr. gets extra gold stars for not allowing comments on his blog, so no one gets to point out why Monckton is full of the brown stuff.

  • fred // April 11, 2008 at 7:21 pm

    Does anyone, anyone at all, have any views on whether the following simple statement is true:

    1995 estimates:
    direct forcing 4.44
    feedbacks 3.56
    sensitivity 1.80

    2001 estimates:
    direct forcing 3.71
    feedbacks 5.89
    sensitivity 2.59

    2007 estimates:
    direct forcing 3.47
    feedbacks 7.20
    sensitivity 3.08

    That is, as time has progressed, if this is true, the IPCC seems to have concluded that the climate is a lot more sensitive to CO2 doubling than it had at first thought, but that this sensitivity is less made up of direct forcing, and a lot more made up of feedbacks.

    Does this, if true, really not strike anyone as interesting or worth the slightest comment? Even if its pointed out by a guy wearing a kilt?

    [Response: Are these forcings due to doubling CO2?

    The IPCC AR4 states that the direct radiative forcing due to doubling CO2, averaged over all models, is 3.80 longwave, -0.13 shortwave, for a net of 3.67 . That's not 3.47. So my first thought is that the most important phrase in your comment is, "if true."]

  • Hank Roberts // April 11, 2008 at 9:38 pm

    > whether the following simple
    > statement is true ..
    > …
    > if this is true, the IPCC seems to
    > have concluded

    There’s a step missing in your logic.

    Are you attributing the numbers you posted to a source? Does that source attribute them to the IPCC?

    Cite, please?

  • Hank Roberts // April 11, 2008 at 9:40 pm

    Searching, this is close but not spot on:
    http://homepages.see.leeds.ac.uk/~earcs/mrespea/archive/2006-Andrews-dissertation.pdf

  • fred // April 11, 2008 at 10:32 pm

    Hank R, yes, the source is the Monckton posting on Pielke. Sorry, I thought that was clear. And yes, the source is attributing these numbers to the IPCC in different years.

    Yes also, Monckton seems to be attributing the direct forcing to CO2 doubling. That is what the post seems to be saying, that he is following the IPCC of the dates mentioned in doing this.

  • TCO // April 11, 2008 at 10:45 pm

    (Respectful request) Tamino, please don’t use the term “swiftboating”. You and I have different opinions on Senator Kerry’s USN service (I know some of his mates). I respect that you think you’re right, but we are on different sides and neither one of us thinks that debating this stuff will be on topic.

    [Response: Request denied.]

  • dhogaza // April 11, 2008 at 11:13 pm

    Well, Fred, did you notice that he simply decides that the lower CO2 forcing estimated by AR4 combined with the lower estimate for feedback from 1995 is the “correct” figure for the net change due to a doubling of CO2?

    And then he reduces this due to Spencer’s latest paper which Spencer claims revitalizes the Lindzen “iris effect”?

    And then reduces it AGAIN based on Lindzen’s “iris effect” hypothesis?

    If another author claims to support Lindzen, will he reduce the figure a third time?

    And nowhere does he discuss error bars (which would reveal that the lower 1995 figure for CO2 forcing which he prefers come with much wider error bars than those for the lower but more tightly bound AR4 figure)?

    I haven’t checked his arithmetic or his numbers. You don’t need to in order to see how misleading and skept-rdish this is.

    Ask yourself why Pielke Sr. would give voice to such garbage.

  • Hank Roberts // April 11, 2008 at 11:14 pm

    Check Monckton’s cite, see if he is quoting correctly.

  • dhogaza // April 11, 2008 at 11:20 pm

    So, Fred, what’s your opinion of this statement by Monckton:

    Set aside the self-evident truth that adaptation as (and if) necessary would be orders of magnitude more cost-effective than mitigation, a conclusion that tends to be overlooked

    Self-evident truth?

    Sorry, the self-evident truth is that in 10 years all the water’s going to boil out of the oceans and it will be venus Earth!

    See? Two can play that game … bwa-ha-ha-ha.

    Get the point, Fred?

  • dhogaza // April 11, 2008 at 11:53 pm

    Oh, I just realized that “skept-rdish” could be misunderstood as a reference to the previous label that some found offensive.

    I had a different vowel than “a” in mind, and since HB doesn’t care for vulgarity on is blog, wrote it “-”.

  • Hank Roberts // April 12, 2008 at 3:46 am

    Just say ’stooge’ — the word has an impeccable pedigree (it’s Lindzen’s aptly cautionary term, as passed on by Judith Curry). And it’s a caution to all of us.

  • dhogaza // April 12, 2008 at 4:15 am

    Just say ’stooge’ — the word has an impeccable pedigree

    Stooge has a varied background. It was in common usage among British POWs during WWII with a meaning equivalent to “lookout”, i.e. a POW lookout that warned those working on tunnels and the like of approaching German guards.

    So I’d prefer some sort of term that can’t be interpreted to have a positive meaning …

    Though of course I’m aware that modern dictionaries seem to be unaware of the WWII Brit POW slang…

  • Lost and Confused // April 12, 2008 at 5:42 am

    Tamino, after seeing that presentation I looked to see if what you said was true, that the erosion was caused by global warming. I was unable to find anyone or anything saying the collapse at Daniel’s Harbour was caused by global warming. I find it implausible that global warming could be faulted, when erosion is a natural thing in a place like that. It would take quite a bit to convince me that was the case, and I have seen nothing to indicate it.

    I know of at least two important statements in An Inconvenient Truth that are complete lies. Al Gore never corrected them. I will never be able to respect him until he admits these sort of mistakes. As of now, he has lied to millions of people.

    [Response: Of course erosion is a natural process. But the rate at which it happens is profoundly affected by the amount of sea ice and the melting of permafrost. But I guess if you were unable to find evidence, then it must not exist. And if you find it implausible, then it must be false.

    As for Al Gore lying, I don't believe you. Put up or shut up. But if you decide to carry on with this, take it to the open thread.]

  • fred // April 12, 2008 at 7:26 am

    I’ve no opinion (yet) on the merits of reduction of warming versus adaptation to it. It is a huge totally different topic.

    I’m simply interested by the way in which the IPCC view of the forces making for warming has apparently changed in the last 10-15 years. Its rising importance in the argument does reinforce my prior intuition that feedback is the critical issue. Get to the bottom of this, and we will be able to make a proper assessment of the AGW hypothesis.

    Or I will. I realize you guys already think you have done all that…

    [Response: I'm actually offended by your naivete (and that's the kindest word I could think of). The very idea that whether or not IPCC estimates of climate forcing and feedback have changed over the years enables one to "make a proper assessment of the AGW hypothesis" is idiotic.

    I guess the fact that estimates of the gravitational constant have changed over the years, with each new research reporting a different value, enables us to make a proper assessment of general relativity? Of course not. It only gives denialists a method to impugn climate science. EVEN IF those numbers are correct, it doesn't mean anything other than scientists are constantly refining their estimates of numerical quantities.

    And I seriously doubt that those numbers are correct. There've been comments here suggesting that he has *deliberately* massaged them to try to make the IPCC look bad. Well I *have* read some of his past works, before I knew about him, and it would fit perfectly with his existing pattern.

    And now you have the *gall* to come here, not even bother to find out if it's true or not, but expect US to do the work, to find the numbers in the IPCC reports? Go read the IPCC reports, find the numbers for yourself, and YOU tell US. And be sure to give chapter and verse, because after this episode I doubt folks will want to take your word for it.]

  • Hank Roberts // April 12, 2008 at 4:14 pm

    The slides — one Alaska, one Newfoundland — are at 6:56 on the video of Gore’s new slideshow from the TED talk.

    Remember Canadian spelling: “harbour” will find the latter story.

    These are cases of accelerated erosion undercutting banks that have been stable for long enough to build on them. What’s changed? Melting permafrost; melting sea ice. Longer periods of time when there’s water rather than ice next to soil that’s less solidly frozen. More wave action against the cliffs.

    ———-excerpt————–

    “… this is the first time emergency measures officials have dealt with such a slide in Newfoundland and Labrador.
    A landslide last October …

    The cliff stabilized over the winter, but thawing soil in recent weeks has been cited as contributing to the latest slides.

    Scientists have noted that the cliff — based not in the bedrock commonly seen across Newfoundland but in clay — was heavy at the top, and eroded at the bottom.”
    ———end excerpt———-
    http://www.cbc.ca/canada/newfoundland-labrador/story/2007/04/19/daniels-harbour.html

    Is it different in the areas where warming is happening the fastest and the transition from ice to water is changing the environment fastest?

    Compare, say, California — geologically rapidly uplifted, poorly consolidated marine sedimentary rock beach cliffs along much of the coast. There, the landslides have been going on rather steadily over the longer term.

  • David B. Benson // April 12, 2008 at 6:56 pm

    Factlet: The acceleration due to gravity acting alone near the surface of the earth at sea level is

    9.80665 m/s

    not corrected for geodesy in the vicinity for which the value is required.

  • chriscolose // April 15, 2008 at 3:37 pm

    Tamino–”ice sheets fall into the “slow” rather than “fast” category.”

    Sea ice and snow are “fast”, ice sheets are “slow”

  • curious // May 23, 2008 at 11:49 am

    Excellent article , thank you (from Spain).

    I also appreciate your answers to the misinformative comments, though I understand it must be weary.
    Thnx

  • Curioso // May 24, 2008 at 12:55 am

    Among skeptics, I’ve also heard of some possible negative feedbacks on which I haven’t found much information on the net (I translate from a Spanish forum, I hope it makes sense, because I’m not an expert) :

    - A temerature rise in the Norwegian region might decrease (as it already happened in the past) deep water generation, or even stop it, as an effect of the stratification of the surface water, or because there are less difference in temperature between the Caribbean region and Norway, and therefore the Gulf Stream slows-down. This slow-down, or even shut-down of the deep waters generation would have a global influence on the Thermohaline circulation (Conveyor Belt), that distributes energy and nutrients throughout the planet. A slow-down of the Thermohaline Circulation would lead to a decrease in global temperatures, as there wouldn’t have a transfer of heat between tropics and poles. Therefore, a temperature increase might lead to a decrease in the medium term.

    *I’ve read that the Gulf Stream is wind-driven and that a slow-down of the Thermohaline Circulation would only have a regional cooling effect (on northern Europe), but I don’t know.

    - A warming period can lead to a massive release of icebers over the Atlantic (similar to the past Heinrich events). This would decrase the temperature in the Atlantic Ocean and may affect the deep water generation in the Mediterranean (as it already happened in the past).

    - Albedo may not vary so much, as there are less albedo in the poles, but more in the tropics, because of the clouds and desertification.

    *I know that most scientists think that clouds would be a positive feedback, though it seems to keep a lot of uncertainty.

  • curious // May 24, 2008 at 1:08 am

    *Regarding what I’ve just posted, I don’t know if “deep water generation” is correct, “deep water formation” sounds better to me right now (though I guess I made many other mistakes)…

  • kim // May 24, 2008 at 5:54 am

    Uh, T, I think you misunderstood Fred. He was saying that ‘feedback’ is the critical issue. He suggests getting to the bottom of that issue, not getting to the bottom of the IPCC’s attitude. I suspect you are blind to the problem of water vapor and ‘feedback’, but still, just read what he wrote.
    ======================

Leave a Comment