Dear David-- On the issue of uncertainties, indeed they exist, but their importance really depends on the question being asked--on the largest questions, things are quite clear; on the smallest scales, departures from the large-scale averages remain somewhat uncertain. [The recent paper by David Rind (The Consequences of Not Knowing Low- and High-Latitude Climate Sensitivity--Bulletin of the AMS) should also be thought of as an augmentation to the IPCC section you mention.]
On testing models, I assume you are aware of the Climate Prediction project that has been running a good GCM many times with variations of its key adjustable parameters (see http://www.climateprediction.net/). Again, the large-picture is very convincing--the finer scale not so much. I would just relate one story about uncertainties from an event in about October 1997 (so just before Kyoto meeting). Pat Michaels and I appeared before the Virginia Coal Council to present our views of the science (me presenting IPCC and Pat offering a critique). Indeed, there were differences in the projections of future warming ranging from maybe 1-5 C by the end of the 21st century. Several of the next speakers spoke about the likely cost of reducing emissions, and the industry economist view was something like $200 a ton whereas the CEO of a utility company said they were sequestering carbon in reforestation projects in South America at $5 a ton. I think these results made clear that it is uncertainties in other parts of the problem that are larger and matter most. The best comment on uncertainties, however, was by the head of the coal miners union, whose comment was that all these uncertainties don't matter a whit--what matters is what the Administration believes (clearly, he understands politics). Indeed--on this issue, I agree that the key issue is not the details of the numbers, but whether we are going to commit to make the change away from GHG-releasing energy technologies. We've now waited so long (recall, the first report to the US President on this was in 1965) to do much that we need to do a lot quite rapidly--and in figuring out that path, the numbers all seem to point to using a whole portfolio of approaches if we are to get where we need to be, and even then we might well benefit from some (even some significant) geoengineering. Mike On 9/22/08 11:34 AM, "David Schnare" <[EMAIL PROTECTED]> wrote: > > Mike: > > Thanks for your thoughtful response. With regard to the ocean sink, > I'm not sure the dynamics of that are quite ready for prime time. > After all, the bouy data shows no statistically significant warming at > any thermocline, and we should be seeing that by now, according to the > IPCC. > > As for integration of regression data into climate models, I think > your representation of the IPCC work goes a bit too far. Take a look > at the discussion on uncertainty in Chapter 10 (10.5.1). The fact is, > until someone runs a monte carlo simulation of a good GCM (probably > requiring about 50,000 to 150,000 itterations), allowing each > assumption to vary within their probability distributions, we are not > going to understand whether the models are giving us measures of > central tendency, or whether they are being manipulated by biases > (known and unknown, intended and unintended). The "ensemble" work is > faulty from its conceptual inception, and can not replace direct > analysis of assumptions. > > Now, I know that no one has the time or money to do the kind of > simulations on GCMs that the rest of the modeling world takes as a > requisite given in validating models, but that leaves the > uncertainties large and the regression analysis an important > validating tool for GCM projections. > > We are now well off-topic for this group, so I'll leave it at that. > > David. > > > On Mon, Sep 22, 2008 at 10:36 AM, Mike MacCracken <[EMAIL PROTECTED]> > wrote: >> The Douglass et al paper (so 2007 instead of 2006) I was referring to was: >> >> Douglass DH, Christy JR, Pearson BD, Singer SF. 2007. A comparison of >> tropical temperature trends with model predictions. International Journal of >> Climatology 27: doi:10.1002/joc.1651. >> >> This is a paper also about tropospheric temperature trends and has both >> Douglass and Christy as authors. And the much better and extensive analysis >> that rebuts it is by Santer et al. 2008: Consistency of modelled and >> observed temperature trends in the tropical troposphere. International >> Journal of Climatology. In press. >> >> I did not mean to infer they ignored volcanic aerosols--fine to take them >> out as one has dates of volcanoes. But near as I could tell they ignored >> sulfate aerosols in the troposphere, which (by IPCC) are an important offset >> to the GHG warming influence. Near as I could tell--they did not account for >> their direct or indirect effects. >> >> As to merging the results of regression analysis and model projections (or >> model performance), that is exactly what is done by the detection and >> attribution studies that the IPCC has devoted a chapter to in at least the >> last three assessments--and this last one shows quite good agreement for >> various regions of the world). I would note that the models take care of >> things like ocean heat capacity, so the thermal inertia (recall that >> something like 90% of the retained heat is in the ocean, and that takes time >> to build up). Indeed, the models have uncertainties in their representations >> of tropospheric sulfate aerosols, but they do find that they make a >> significant negative contribution to the forcing (that is, they lead to some >> solar radiation being reflected to space). >> >> And on the paper, to end with a positive, it was nice to see that they find >> do agree that solar radiation was decreasing as the world was warming--so is >> not a factor in recent warming. >> >> Best, Mike >> >> >> On 9/21/08 10:40 PM, "David Schnare" <[EMAIL PROTECTED]> wrote: >> >>> >>> Well, Mike, tell us how you really feel. >>> >>> If you want to dump on J.J. Hnilo (Program for Climate Model Diagnosis >>> and Intercomparison, Lawrence >>> Livermore National Laboratory, Livermore, California) and Bob Knox >>> (Thermocline flux exchange during the Pinatubo event," D. H. Douglass, >>> R. S. Knox, B. D. Pearson, and A. Clark, Jr., Geophys. Res. Lett. 33, >>> L19711, doi:10.1029/2006GL026355 (2006)), that's up to you. They >>> looked the paper over before it went to the journal and seemed to find >>> it worthy of publication. >>> >>> As for your points, they don't all match up with the paper. Douglass >>> and Christy did a standard regression analysis, pulling out those >>> elements from the variation they knew were unrelated to CO2, including >>> stratospheric aerosols. They didn't ignore them. >>> >>> Ken: I'm not sure what your point is. When I was attacked at a >>> climate change commission meeting while suggesting that climate >>> geoengineering is an insurance policy into which we should put >>> significant research dollars, the IPCC author argued that the models >>> underlying that approach were wildly uncertain. When I reminded him >>> they were the same models used to support some of the IPCC work, he >>> took affront. >>> >>> The problem that has not been addressed within the climate science >>> community is the conflict between using GCMs to predict outcomes, and >>> using regression analysis to define the determinants to future >>> behavior. They ought to support each other, but they don't seem to do >>> so with any level of robust confidence. Those of you who spend a lot >>> of time with models might find it helpful to try to meld these two >>> approaches. Until one group or the other does so, there will continue >>> to be a basis for uncertainty about either approach. Heck, Ken, you >>> might even call that skepticism. It's a science thing. I guess that >>> can be amusing. For me, its just frustrating because both approaches >>> have a legitimate science basis and neither explains the outcomes of >>> the other. >>> >>> David. >>> >>> On Sep 21, 2:57 pm, "Ken Caldeira" <[EMAIL PROTECTED]> wrote: >>>> It is amusing that some climate skeptics seem to accept climate science >>>> when >>>> it says that climate engineering schemes will to some extent work but are >>>> less willing to accept that same science when it says that human-induced >>>> global warming is real. >>>> >>>> It is like accepting modern medicine while denying Darwinian evolution. >>>> >>>> On 9/21/08, Mike MacCracken <[EMAIL PROTECTED]> wrote: >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>>> Dear David--You must be kidding when you say we should be looking at this >>>>> paper. The last paper by Douglass et al ended up being thoroughly rebutted >>>>> (or article is about out) as a result of very poor statistical practices; >>>>> this journal is known to have no serious peer-review (that the authors are >>>>> submitting it there says something already about the quality of their >>>>> argument--the analysis not being good enough even in their mind to be sent >>>>> to a better journal); etc. >>>> >>>>> Among the obvious problems: >>>> >>>>> 1. So, if I get surface warming that involves the weakening of an >>>>> inversion--such as is occurring across the polar regions--that >>>>> contribution >>>>> to warming should be of no concern or interest or influence--all that >>>>> matters is the change of tropospheric temperature. The authors seem to be >>>>> considering a 1-D world where the whole troposphere and surface are fully >>>>> and continuously connected by convection, night and day, year around for >>>>> all >>>>> latitudes. Sorry, but that is not the case, and we live at the surface. >>>> >>>>> 2. The authors argue that the effects of tropospheric sulfate aerosols can >>>>> be totally ignored--suggesting that they have no influence on temperature >>>>> (but somehow soot ones do, and so do volcanic aerosols). If they had maybe >>>>> argued they were getting the net warming effect together of all changes in >>>>> greenhouse gases, all types of aerosols, and land use combined, as >>>>> distinct >>>>> from ENSO influences (which can of course be being influenced by human >>>>> influences--whether as a result of warming or changes in latitudinal >>>>> gradients of forcing and ocean heating), then this paper might deserve a >>>>> wee >>>>> bit more of a look. >>>> >>>>> 3. And then there is no apparent consideration of ocean lag effects--so >>>>> this >>>>> is an analysis of the warming we see now and from this they conclude that >>>>> there is no feedback as if the climate is at equilibrium and would not >>>>> warm >>>>> anymore if all forcings stayed constant. Sorry, but the ocean has a lot of >>>>> heat capacity. >>>> >>>>> And if I misstated things it is because I had already spent too much time >>>>> just skimming the article. Apologies. >>>> >>>>> Mike MacCracken >>>> >>>>> On 9/21/08 12:47 PM, "David Schnare" <[EMAIL PROTECTED]> wrote: >>>> >>>>>> Douglass and Christy have tested the IPCC argument that "most of the >>>>>> observed increase in global average temperatures since the mid-20th >>>>>> century is very likely due to the observed increase in anthropogenic >>>>>> greenhouse gas concentrations,² and demonstrated this statement is >>>>>> false at a 95% confidence interval. The underlying temperature >>>>>> increase due to CO2 appears to be no greater than 0.7 deg C per >>>>>> century. I commend the paper to you. It is available at >>>>>> http://arxiv.org/ftp/arxiv/papers/0809/0809.0581.pdf. >>>> >>>>>> (Accepted by Energy and Environment Aug 2008) >>>>>> Limits on CO 2 Climate Forcing from Recent Temperature Data of Earth >>>>>> David H. Douglass a and John R. Christy b >>>> >>>>>> Summary: >>>>>> The recent atmospheric global temperature anomalies of the Earth have >>>>>> been shown to consist of independent effects in different latitude >>>>>> bands. The tropical latitude band variations are strongly correlated >>>>>> with ENSO effects. The maximum seen in 1998 is due to the El Niño of >>>>>> that year. The effects in the northern extratropics are not consistent >>>>>> with CO2 forcing alone >>>>>> An underlying temperature trend of 0.062±0.010ºK/decade was estimated >>>>>> from data in the tropical latitude band. Corrections to this trend >>>>>> value from solar and aerosols climate forcings are estimated to be a >>>>>> fraction of this value. The trend expected from CO2 climate forcing is >>>>>> 0.070g ºC/decade, where g is the gain due to any feedback. If the >>>>>> underlying trend is due to CO2 then g~1. Models giving values of g >>>>>> greater than 1 would need a negative climate forcing to partially >>>>>> cancel that from CO2. This negative forcing cannot be from aerosols. >>>>>> These conclusions are contrary to the IPCC [2007] statement: ³[M]ost >>>>>> of the observed increase in global average temperatures since the >>>>>> mid-20th century is very likely due to the observed increase in >>>>>> anthropogenic greenhouse gas concentrations.² >>>> >>>> -- >>>> =============================== >>>> Ken Caldeira >>>> Department of Global Ecology >>>> Carnegie Institution >>>> 260 Panama Street >>>> Stanford, CA 94305 USA >>>> +1 650 704 7212; fax: +1 650 462 5968 >>>> >>>> [EMAIL PROTECTED] >>>> >>>> http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab/ >>>> >>>> *** Please don't read this line of text unless you really need to ***- Hide >>>> quoted text - >>>> >>>> - Show quoted text - >>>>> >> >> >> > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. 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