Steve (cc Geo List and more ccs - adding Dr. Wasdell) 1. Thanks for making your helpful Science paper available for all.
2. I started the latest part of this thread (because Ken kindly referenced your joint paper a few days ago) - so hope you don't mind my carrying my interest a bit further. My reason for including data from your figures 1 C and D was that I am trying to tie down the big discrepancy in climate sensitivity that I find in the climate modeling literature. Using your data, it seems that the (University of Victoria) model you were using employed a sensitivity a little less than the "Charney sensitivity" value of 3, as I compared three of your CO2-temperature pairs with Dr. Wasdell's material (referenced below). 3. I am afraid my remarks could be interpreted to mean that your numbers could be off by the factors of 2.5 and 3 that I used in comparing to higher predictions of this important sensitivity parameter by Drs. Hansen and Wasdell. I didn't intend that and don't think it true - as you were starting with a 2010 pair that are presumably pretty well known (390 ppm and 0.95 degrees). Although the model probably was not including much if any Arctic ice melt (and albedo change), the rapid draw down would perhaps not allow much growth in global temperature (unless we have already passed a/the tipping point) 4. Some questions: Q1. Do you (anyone reading this) think that the present climate sensitivity today is higher than apparently is in the model? I.e. - might the highest temperature point in your Figure 1D more likely be off the chart rather than at1.4 degrees? If so, can these models be run with increasing climate sensitivity (increased positive feedback) over time? Q2. Assuming that the model has done a good job in recreating the present situation of an 0.95 degree rise with its use of a sensitivity of less than 3, what time path is involved in getting to the sensitivity values of 6 and 8 predicted by Drs. Hansen and Wasdell. Decades, centuries, or millenia? and how can we predict this accurately? Q3. In your Figure 1C, the three ppm curves peak well before carbon dioxide emissions have gone to zero - which could presumably only occur if there was some carbon negative technology already also in place. Was that the case? Could the model include the 2ppm annual drawdown that Dr. Hansen attributes to 100 Gt C of new forests? Q4. In Figure 1D, the temperature curves flatten even though the CO2 ppm data is still generally above today's 390 level. That is, we hear about built in future "heritage" temperature rises that apparently are not much in this model. Any explanation? 3. I recognize that you had to work with an existing (Victoria) model - so these above are questions you may not be able to answer. But you are much closer than most of us to the modeling world - and it would help us to understand what could be an underestimate. Dr. Wasdell has listed quite a few positive feedbacks that have had to be left out of even the biggest models (such as meltinc Arctic ice and clathrate emissions). My question is how many we can already see in play and can models get a time-increasing "fudge factor" to account for these? 4. Lastly, your own personal site is quite interesting. I have signed up for your e-letter from the new NGO you head. The rest of the day will be on your (with Dr. Burney) PNAS paper of ag intensfication - which I am hoping is highly relevant to CDR. Again, thanks. Ron ----- Original Message ----- From: "Steve Davis" <[email protected]> To: "Ken Caldeira" <[email protected]> Cc: "Andrew Lockley" <[email protected]>, [email protected], "geo-engineering grp" <[email protected]>, "Steve Davis" <[email protected]> Sent: Tuesday, July 26, 2011 8:45:15 AM Subject: Re: More detail per list member request I believe the paper can be accessed for free from my website: http://www.stanford.edu/~sjdavis/ Best, Steve On Jul 26, 2011, at 3:09 AM, Ken Caldeira < [email protected] > wrote: Not considering everything under the sun is not a problem with our paper, it is what makes a scientifically defensible quantification possible. We note in the paper that in quantifying future co2 emissions from existing co2-emitting devices, we are quantifying only a piece of infrastructural commitment. We started that paper thinking we would show that existing co2-emittig devices were enough to send us over 450 ppm and 2 c. We never intended to present s realistic scenario. I believe that existing infrastructure that does not directly emit co2 (eg automobile factories), not to mention political inertia, are enough to push us beyond these levels (in the absence of dramatic political change and engineering effort). Sometimes, when writing scientific papers, it is better to answer a limited question well rather than answer a broader question poorly. Scientific papers are like statements in a discussion. We generally try to say the first word on a topic, not the last word. Insofar as different sources of commitment can be quantified in a technically defensible way, I encourage others to do so. If we think of a good way to do so; hopefully we will beat you to it. When i have access to my laptop, I will send a copy of the paper. Ken Caldeira [email protected] + 1 650 704 7212 http://dge.stanford.edu/labs/caldeiralab Sent from a limited-typing keyboard On Jul 26, 2011, at 11:25, Andrew Lockley < [email protected] > wrote: thanks for that. I forwarded it. The Caldeira paper has the problems anticipated, ie that the political/construction/sociological trajectory isn't included. There's no way China can stop it's emissions growth dead. It's simply not going to happen. I couldn't see the other graph, it didn't come out very well. I assume it's dt vs CO2e ppm. I maintain that the evidence supports SRM as plan A A On 26 July 2011 04:54, < [email protected] > wrote: Andrew - This is to ask you to forward the following to the geo list. I am sure it won't be successful from my computer These further provide detail on the diagrams that a geo list member has asked for (and in the "Word" attachment) List and Andrew As a subscriber to (behind a pay-wall) Science magazine, I was asked if I could provide the graphs I was working with from the Davis-Caldeira paper I commented on a few hours ago. I think this should not violate any copyright prohibitions - and might even sell more for the journal Science (my favorite). The necessary three data point-pairs are the right most in parts C and D (I couldn't find a way to remove A and B.). These 3 point-pairs for the year 2060 can then be put in the (free) material I referenced by Dr David Wasdell. - found at http://www.apollo-gaia.org/Climate_Sensitivity.htm . The second graph is taken from the attachment article by Dr. Wasdell that you provided on 20 July. This is the best copy I could find/copy. If one rotates it CCW, one will find that the horizontal axis runs from 140 ppm to 560 ppm with 280 ppm in the middle, plotted on a log base 2 scale. The three point - pairs will be found to lie to the left of the 440 ppm dotted line and below the "Charney" diagonal - a region that Dr. Wasdell says mis-reads the historical evidence. I hope this is helpful. Ron -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en.
