tag:blogger.com,1999:blog-2313427464944392482.post5328468814945697235..comments2019-08-24T23:04:50.497+10:00Comments on HotWhopper: Wondering Willis Eschenbach is uncertainly sensitive at WUWTSouhttp://www.blogger.com/profile/08818999735123752034noreply@blogger.comBlogger9125tag:blogger.com,1999:blog-2313427464944392482.post-53985095532004333092013-10-04T03:23:18.423+10:002013-10-04T03:23:18.423+10:00We may be talking at cross purposes a little here ...We may be talking at cross purposes a little here :-)<br /><br />Consider Kiehl's equations 3 and 4. Equation 3 is<br /><br />Delta Q = (Delta T Delta Q_2x)/Delta T_2x _+ H<br /><br />Delta Q is the change in forcing. Delta T is the change in temp. H is the ocean heat uptake rate. Delta Q_2x is the change in forcing for a doubling of CO2. If I understand this correctly, from observations Delta T = 0.6 degrees. H = 0.7 W/m^2. Delta Q_2x = 3.7 W/m^2. You can plug in the constants and you get Equation 4<br /><br />Delta Q = 2.22/Delta T_2x + 0.7<br /><br />Kiehl then uses this to produce the curves in Figure 1 and it shows an inverse relationship between change in forcing (Delta Q) and ECS (Delta T_2x). The point that I was trying to make (maybe not very clearly) is that what Kiehl has done here doesn't seem (as far as I can tell) to provide any physical mechanism for this relationship. It really just comes from the observational constraints (fixed Delta T, fixed H and Delta Q_2x). So, as I think you're saying, you need some other forcing that changes from model to model (aerosols) that can result in those models with different changes in forcings (Delta Q) and climate sensitivities (Delta T_2x) having the same change in temperature (Delta T).<br /><br />Anyway, I think you're quite right and I was just trying to make an observation about the relationship that Kiehl found between Delta Q and Delta T_2x. Wotts Up With That Bloghttp://wottsupwiththatblog.wordpress.comnoreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-25146556354380534722013-10-04T02:15:16.079+10:002013-10-04T02:15:16.079+10:00I think I understand what you are saying but I'...I think I understand what you are saying but I'm not 100% sure.<br /><br />If two models show the same temperature rise over the same period for the same CO2 forcing but predict different climate sensitivities then an inverse correlation between total forcing and sensitivity is implied, isn't it? The two notions are one and the same. The thing is to find out why - and Kiehl attributed it to differences in aerosol forcing.<br /><br />Model A predicts high sensitivity. Model B predicts low sensitivity. Both Model A and Model B show the the same temperature rise over the same period while the CO2 forcing was identical. Therefore either Model A must include some effect that is counteracting the (higher) CO2 forcing (eg incorporating a larger negative aerosol forcing) or Model B must be including something that is adding to/subtracting less from the CO2 forcing for the period in question (eg incorporating a much lower negative aerosol forcing). <br /><br />Remember aerosol from smog or volcanoes is a forcing not a feedback and is negative. It reflects incoming radiation. So it counteracts the positive forcing of CO2.<br /><br />Like I said, this can do your head in :DSouhttps://www.blogger.com/profile/08818999735123752034noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-64229027772851516992013-10-04T02:02:49.470+10:002013-10-04T02:02:49.470+10:00Actually, I should have read Knutti more closely i...Actually, I should have read Knutti more closely in that it says <br /><i><br />There is no correlation between the climate sensitivities of the CMIP3 models and their respective heat uptake efficiencies (the heat flux into the ocean per unit global surface warming at the point of CO2 doubling in a1%/yr CO2 increase scenario)<br /></i><br />So, maybe fixing <i>H</i> is kind of consistent with the models anyway. That would seem to imply something with respect to other forcings and feedbacks though (I would think) but maybe I should just give up for the day as I seem to be getting myself more and more confused :-)Wotts Up With That Bloghttp://wottsupwiththatblog.wordpress.comnoreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-8150245071882404522013-10-04T01:53:51.434+10:002013-10-04T01:53:51.434+10:00Sorry, I wasn't commenting on your post or cri...Sorry, I wasn't commenting on your post or criticising your analysis of Kiehl as such (which I should probably have made clearer :-)). I was simply making a comment about how I found the curves in Kiehl (2005) a little strange (in that a lower adjusted forcing produced a higher ECS). What Knutti (2008) says makes sense although it just seems to be suggesting that you can get the same net warming (over some time interval) using models with different sensitivities but that have different net forcings (through variations in aerosol feedbacks for example). It's not clear how Kiehl concludes this because the function he uses to fit the data depends only on the adjusted forcing and the heat uptake of the system (H) so any aerosol influence is implicit and the reason he seems to get the curves he gets is simply because it depends inversely on Delta T_2x and everything else is fixed.<br /><br />Admittedly, I've been getting most things wrong today, so maybe I'm wrong about this too :-)Wotts Up With That Bloghttp://wottsupwiththatblog.wordpress.comnoreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-67918029046659912162013-10-04T01:39:04.488+10:002013-10-04T01:39:04.488+10:00Yes, I think I got it fairly right. From Knutti (...Yes, I think I got it fairly right. From <a href="http://www.image.ucar.edu/idag/Papers/PapersIDAGsubtask1.3/knutti_climate_models.pdf" rel="nofollow">Knutti (2008)</a><br /><br /><i>Kiehl [2007] recently showed a correlation of climate sensitivity and total radiative forcing across an older set of models, suggesting that models with high sensitivity (strong feedbacks) avoid simulating too much warming by using a small net forcing (large negative aerosol forcing), and models with weak feedbacks can still simulate the observed warming with a larger forcing (weak aerosol forcing).</i>Souhttps://www.blogger.com/profile/08818999735123752034noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-79500611494178130232013-10-04T01:18:59.561+10:002013-10-04T01:18:59.561+10:00I think you're right about the models, althoug...I think you're right about the models, although there is quite a lot of scatter. I was mainly referring to his curves that just seemed a little odd (although they kind of fit the model results but I suspect the fit is not that good, statistically). Maybe the assumption is right but, mathematically, his curves come from fixing the term representing the energy imbalance.Wotts Up With That Bloghttp://wottsupwiththatblog.wordpress.comnoreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-5859424991341845712013-10-04T01:03:23.845+10:002013-10-04T01:03:23.845+10:00I'll add that my head started to spin a bit wh...I'll add that my head started to spin a bit when I tried to unravel all this, so I could have Kiehl's paper wrong too :)Souhttps://www.blogger.com/profile/08818999735123752034noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-46999680321565131142013-10-04T00:58:29.278+10:002013-10-04T00:58:29.278+10:00The reason that paper found that result was becaus...The reason that paper found that result was because it was predefined in the models he looked at. In other words, he looked at papers that showed different climate sensitivity over the same historical period, when obviously the temperature rose the same amount and so did CO2. <br /><br />He then looked at what might have contributed to the difference in climate sensitivity and settled on differences in aerosols. (He also wrote: This strongly suggests that the scatter among the models is mostly due to the range in modeled change in ocean heat storage.)<br /><br /> I don't know if he looked at other areas of uncertainty eg cloud cover but I didn't see anything like that in the paper.Souhttps://www.blogger.com/profile/08818999735123752034noreply@blogger.comtag:blogger.com,1999:blog-2313427464944392482.post-21774925268515714272013-10-04T00:51:12.840+10:002013-10-04T00:51:12.840+10:00I've just written a post about observational c...I've just written a post about observational constraints which (thanks to Karsten) I've realised is mostly wrong. It was, however, motivated by the Kiehl paper which has a plot showing that the ECS is larger when the adjusted forcing is smaller. This all seemed rather strange to me but I think is simply because the analysis assumes that the current heat uptake of the system (energy imbalance) is always the same and hence the method (given that it depends inversely on the adjusted forcing) produces a higher ECS for a lower adjusted forcing. So, the result in Kiehl seems to be strongly influence by that one assumptions which doesn't seem obviously well founded (i.e., if the adjusted forcing was actually lower you might expect the current energy imbalance to also be lower).<br /><br />Anyway, Willis seems to end all his posts with a comment along the lines of<br /><i><br /> I think the whole concept of “climate sensitivity” is meaningless in the context of a naturally thermoregulated system such as the climate.<br /></i><br />which means, as far as I can tell, that Willis thinks our climate is controlled by something magical (or something as yet unknown) so I've taken to largely ignoring what he writes.Wotts Up With That Bloghttp://wottsupwiththatblog.wordpress.comnoreply@blogger.com