tag:blogger.com,1999:blog-9959776.post4490195453366953255..comments2024-02-15T04:42:41.606+00:00Comments on James' Empty Blog: More Chylek on sensitivityJames Annanhttp://www.blogger.com/profile/04318741813895533700noreply@blogger.comBlogger12125tag:blogger.com,1999:blog-9959776.post-73679280056437230282008-04-01T10:02:00.000+01:002008-04-01T10:02:00.000+01:00OK, thanx for clarifying this.OK, thanx for clarifying this.ErikShttps://www.blogger.com/profile/04698899229265554348noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-84381273911104096702008-04-01T05:28:00.000+01:002008-04-01T05:28:00.000+01:00The albedo they are talking about is the slow grow...The albedo they are talking about is the slow growth and melt of large continental ice sheets over the 1000y time scale. We now have no really big ice sheets to melt (and what we do have are very polar, hence relatively little albedo effect). A change in sea-ice extent, which we will see (already are doing) is counted as a feedback because it is fast. <BR/><BR/>Dust and vegetative albedo are perhaps the hardest to call, as they really ought to change quite rapidly in response to a climate change. But given that so much of the world's surface is under direct anthropogenic influence we can probably dominate these changes with direct action irrespective of what the "natural" response would be. Also, they are expected to be fairly modest, so there is little penalty for ignoring them in future climate change experiments.James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-70194445863320804532008-03-31T16:45:00.000+01:002008-03-31T16:45:00.000+01:00I think I now get it with the CO2 (because the CO2...I think I now get it with the CO2 (because the CO2 concentration is the parameter being set to a certain value in the model estimates), but the albedo change? Should that be included in the RF, as C&L do? As I used to understand things it was positive feedbacks such as albedo and water vapor which made the climate sensitivity high. If you count these into the RF, what is then making the climate sensitivity high?ErikShttps://www.blogger.com/profile/04698899229265554348noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-71625793505357853822008-03-31T14:31:00.000+01:002008-03-31T14:31:00.000+01:00Erik,The forcing/feedback distinction is somewhat ...Erik,<BR/><BR/>The forcing/feedback distinction is somewhat artificial, but their usage is standard. We want the response of the atmosphere-ocean system to a radiative forcing, so that includes the CO2 change.James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-43258969406917785212008-03-31T12:19:00.000+01:002008-03-31T12:19:00.000+01:00OK, I may be wrong here (stupid Swede...), but hav...OK, I may be wrong here (stupid Swede...), but havn´t C&L got the equation for the radiative forcing totally wrong? They are including the CO2-feedback in the forcing, which seems stange to me. Shouldn´t it be lambda = deltaT/(external forcing) rather than lambda = deltaT/(external forcing + CO2 feedback + ...)?<BR/>Please correct me if I´m wrong or give me some award if I´m right...<BR/>/ErikSErikShttps://www.blogger.com/profile/04698899229265554348noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-66775631606340581822008-03-29T19:38:00.000+00:002008-03-29T19:38:00.000+00:00IEHO boreholes are not very good proxys but they m...IEHO boreholes are not very good proxys but they may be the only game in town to go way back (beyond the ice cores). Again, you have to differentiate between useful and perfect.EliRabetthttps://www.blogger.com/profile/07957002964638398767noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-24426152816497138912008-03-29T10:50:00.000+00:002008-03-29T10:50:00.000+00:00Won't looking for natural global signals in S. Hem...Won't looking for natural global signals in S. Hemisphere dust records in the interval after 41KA be fucked up by the contemporaneous anthropogenic aridification of central Australia?C W Mageehttps://www.blogger.com/profile/09706100504739548720noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-3544037159166681732008-03-29T05:46:00.000+00:002008-03-29T05:46:00.000+00:00Heiko,I don't know much about boreholes but I thin...Heiko,<BR/><BR/>I don't know much about boreholes but I think they are probably "rubbishy proxies" to use your term. It must be hard to reliably invert these very small deviations in temperature from a poorly-known background steady state (ie the flow of geothermal heat through a medium that itself has poorly-known properties). For Vostok there is a whole lot of broadly consistent evidence, at least on the longer time scale - and the authors allowed for +- 0.5C of uncertainty for LGM to Holocene temp change, which is probably in the right ballpark.James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-9456386185015451692008-03-28T21:21:00.000+00:002008-03-28T21:21:00.000+00:00A while back I saw an interesting post by Tamino o...A while back I saw an interesting post by Tamino on boreholes, which referenced this database:<BR/><BR/>http://www.geo.lsa.umich.edu/climate/core.html<BR/><BR/>I was interested in arctic temperatures, so I checked out the Northernmost boreholes in N. America and hit these two graphs:<BR/><BR/>http://www.geo.lsa.umich.edu/climate/RECONSTRUCTION/CA-290-1.html<BR/><BR/>http://www.geo.lsa.umich.edu/climate/RECONSTRUCTION/CA-066-0.html<BR/><BR/>One has a downward trend over the last 500 years of 2.5C and the other an upward trend of 3C.<BR/><BR/>Are boreholes really rubbishy proxies?<BR/><BR/>Or does local temperature history vary massively from the world trend? If the latter, how can we use a single proxy for a single place to stand in for world temperature?Heikohttps://www.blogger.com/profile/06839810379331430109noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-85238947302954787202008-03-28T18:54:00.000+00:002008-03-28T18:54:00.000+00:00And to think James, I (nearly) always have moderat...And to think James, I (nearly) always have moderately nice things to say about you :^) !<BR/><BR/>-Chip<BR/>www.worldclimatereport.comChip Knappenbergerhttps://www.blogger.com/profile/10580051919422845463noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-86316550112206873422008-03-27T13:47:00.000+00:002008-03-27T13:47:00.000+00:00I forgot to add ... nice post.I forgot to add ... nice post.Jhttps://www.blogger.com/profile/17585037382114278108noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-43480882303200456332008-03-27T13:43:00.000+00:002008-03-27T13:43:00.000+00:00"I was actually going to write something moderatel..."I was actually going to write something moderately nice about [World Climate Report] (OK, I will anyway, probably over the weekend)."<BR/><BR/>Say something <B>nice</B> about WCR? <BR/><BR/>At least wait 'til Tuesday ... that's the one day of the year when one might be able to justify doing something so silly.<BR/><BR/>:-)Jhttps://www.blogger.com/profile/17585037382114278108noreply@blogger.com