cc: ssmith@ucar.edu date: Fri, 24 Jul 1998 17:42:05 +0100 from: Sarah Raper subject: naki's emissions data to: scenarios@meto.gov.uk Dear all, The emissions data sent out by Naki seem to me to be deficient for a number of reasons ... (1) CO2 emissions need to be split into fossil and net deforestation in order to do carbon cycle modeling. (2) My crucial point about consistency with 'observed' emissions has been ignored. (3) CH4 emissions in 1990 are grossly out of budget balance - even worse that in the IS92 scenarios. (4) 1990 SOx emissions are too low compared with Steve Smith's corrected GEAI data. (5) Global SOx emissions are useless -- it is essential to have a global GRIDDED data set. This is what we have done at NCAR. We are willing to make these data sets available to modelers. In addition, there were some scientific flaws in the letter from Watson et al. For example (read the SAR!) it is not possible (and not necessary!!) to devise a CO2 emissions scenarios from first principles that will stabilize CO2 concentrations. The E-C link depends on the carbon cycle model used -- and I do not believe that all of the emissions generating groups have the same model (or that they have the Joos model in particular). What we did in the SAR is start with the CONCENTRATION profile and derive the emissions, which requires specifying a particular net deforestation scenario. It is possible to do a similar inverse calculation to what was done for the SAR with an energy-economics model -- this is what Steve Smith has done to derive 'our' stabilization cases. I doubt that anyone else has done this -- but perhaps I am underestimating people. Even if I am underestimating people, I can't see how anyone can have done this properly, since no-one has updated concentration stabilization profiles (i.e., profiles that are consistent with observations through the 1990s). Again, I've made the offer to distribute these already. As a final painfully obvious point, modelers DO NOT NEED CO2 emissions data for a stabilization case, since we already have the concentrations! It is the concentrations that go into the model!! The reason why an energy-economics model is needed in such a case is in order to get consistent emissions for non-CO2 gases, especially SO2. You might guess from the above that I was very disappointed by the material distributed by Naki. Please think about the points made above and try again. This is really important data and 'we' can't afford to have it open to the elementary types of criticisms raised here. Constructively (albiet bluntly) yours, Tom Wigley. --------------------------- | Dr S. C. B. Raper | | Climatic Research Unit | | University of East Anglia | | Norwich | | NR4 7TJ | | | | Tel. +44 1603 592089 | | Fax +44 1603 507784 | ---------------------------