Back of an envelope? 'These calculations can be condensed into simplified fits to the data, such as the oft-used formula for CO2:
Radiative Forcing = 5.35 ln(CO2/CO2_orig) (see Table 6.2 in IPCC TAR for the others)... Thus the RF for a doubling of CO2 is likely 3.7±0.4 W/m2.' It says nothing about feedbacks or other forcings or indeed 'abrupt climate change'. Have a look at realclimate for a simplified 6 step exposition. http://www.realclimate.org/index.php/archives/2007/08/the-co2-problem-in-6-easy-steps/ The radiative forcing may even be true - but the overall temperature change very much depends on not having abrupt change. Something that I feel is very much in doubt. On Mar 1, 12:00 pm, "David B. Benson" <[email protected]> wrote: > On Feb 25, 1:06 pm, Robert I Ellison <[email protected]> > wrote:> ... > > The Arrhenius formula is > k(ln(CO2 now) - ln(CO2 start)) > where the start is best treated as an interval fairly > near equilibrium and k is a constant to be determined. > It is ordinarily reported as k*ln(2) for 2xCO2 as a > matter of convention. > > One way to estimate k is using the known concentrations > of CO2 from Law Dome and the Keeling curve and global > temperature anomlies from GISTEMP. I did this using > decades and a sngle decade lag so that the average CO2 > concentration for one decade is used to estimate GISTEMP > average for the following decade. This means not ony > is k=OGTR estimated but it is then possible to offer > a prediction for the decade just now starting. Here it > is > OGTR for 2xCO2 = 2.33 RMS= 0.05 R2= 0.96 > decade GTA AE residual > 1880s -0.28 -0.28 +0.00 > 1890s -0.25 -0.23 -0.02 > 1900s -0.26 -0.20 -0.05 > 1910s -0.28 -0.17 -0.10 > 1920s -0.18 -0.13 -0.04 > 1930s -0.04 -0.09 +0.05 > 1940s +0.03 -0.05 +0.08 > 1950s -0.02 -0.03 +0.01 > 1960s -0.01 -0.00 -0.01 > 1970s -0.00 +0.07 -0.07 > 1980s +0.18 +0.18 -0.01 > 1990s +0.31 +0.33 -0.02 > 2000s +0.51 +0.47 +0.04 > 2010s ??.?? +0.64 > with the value of R squared (R2) indicating that > all but 4% of the variance is explained. > > Since the climate is now far from equilibrium, > the value of OGTR is for the Observed GISTENP > Response to date. There are some rules of thumb > which suggest a range for the equilibrium climate > sensitivity (ECS) based on OGTR; these hint at a > value for ECS in the range 3.3--3.7 K but this > range is not to be taken as more than indicative. -- You received this message because you are subscribed to the Google Groups Global Change ("globalchange") newsgroup. Global Change is a public, moderated venue for discussion of science, technology, economics and policy dimensions of global environmental change. Posts will be admitted to the list if and only if any moderator finds the submission to be constructive and/or interesting, on topic, and not gratuitously rude. 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/globalchange
