date: Tue, 06 Jul 2004 09:28:24 -0600 from: Tom Wigley subject: Re: Question re AR4 and long scenarios to: sraper@awi-bremerhaven.de SARAH -- SEE BELOW .... sraper@awi-bremerhaven.de wrote: >Dear Tom, > >Thanks for input and your recent paper. > >I don't think I know a lot about emissions scenarios but if your >IPCC overshoot scenario example is their level perhaps I am >wrong! > YOU PROBABLY KNOW MORE THAN MOST WG1 PEOPLE. > >I think my role will be to report to and fro between WG1 ch 10? >(projections) and think about what we will present. > YES -- IMPORTANT. > > >Also I may have some leverage in who is invited to the meetings, >but that won't be covered in the teleconference on Thursday I >would think. > >Re carbon cycle feedbacks >1) is it a typo in your abstract - 'carbon feedbacks on the carbon >cycle'? > OOPS -- THANX FOR NOTICING THIS >2) So in the paper you do use carbon cycle feedbacks - I think >this is going to be a big issue in the TAR - how to justify not doing >it.... > YES, NO EXCUSE FOR NOT INCLUDING THESE. HOWEVER, SINCE ALL COUPLED AOGCM/CARBON CYCLE MODELS WILL HAVE THESE DIFFERENT, IT IS BETTER FOR COMPARABILITY (AND TO AVOID OUTLIERS) TO DO THE CO2 OFF LINE. > >The scoping paper seems to cover an aweful lot - >I don't think IPCC TAR delt with mitigation scenarios, WG1 didn't >anyway except for the used before WRE and S profiles (too >political) is this going to change now? > NOT READ THIS YET. > >Any thoughts appreciated. > >Cheers, > >Sarah > SOME OTHER STUFF .... FIRST, WHEN YOU DID THE AOGCM/MAGICC CALIBRATION, DID YOU DE-DRIFT THE 1% RUN DATA? SECOND, I HAVE BEEN WRITING UP SOME STUFF ON COMMITMENTS -- MAINLY TO PRE-EMPT IPCC, SINCE THEY WILL NOT BE ACCOUNTING FOR UNCERTAINTIES. SEA LEVEL IS EVEN MORE OF A PROBLEM THAN I THOUGHT. THERE ARE TWO SERIOUS ISSUES. THE NON-MELT TERM IS LINEAR IN TIME. THIS MEANS IT GETS QUITE BIG AFTER, SAY, 400 YEARS. MAYBE LINEAR IN TIME IS OK TO 2100, BUT AFTER THAT IT COULD BE (IS) RATHER SILLY. THE SECOND ISSUE IS ONE I RAISED BEFORE, DESCRIBED IN THE MAGICC/SCENGEN MANUAL. THE RATHER DUMB JONATHAN METHOD FOR GSICS IMPLIES AN UPPER BOUND FOR MELT, WHICH MUST BE IDENTIFIED WITH THE TOTAL AVAILABLE AMOUNT OF GSIC ICE. THE LIMIT FOR THE CENTRAL CASE IS ABOUT 19cm FROM 1880, WHICH, AS I SAID BEFOR, IS ALMOST CERTAINLY TOO LOW. PERHAPS 50cm IS TOO HIGH (BUT NOT ACCORDING TO MEIER), AND PERHAPS EVEN THE 30cm WE USED IN THE SAR IS TOO HIGH (I THINK YOU SAID IT WAS). BUT ONLY 19cm (OR 17cm FROM TODAY)??!! THIS BECOMES EVEN MORE RIDICULOUS IF ONE USES THE LOW AND HIGH LIMITS RECOMMENDED IN THE TAR. FOR CHANGES FROM 1880 THE LOW IS ABOUT 5cm (WHICH HAS GOT TO BE TOTALLY IMPOSSIBLE), WHILE THE HIGH IS ABOUT 32cm (WHICH, WITHIN THE MANY ACCOUNTING UNCERTAINTIES, HAS ALSO GOT TO BE TOO LOW. THESE ARE COMPENSATING ERRORS -- TOO HIGH NON-MELT AND TOO LOW GSIC. BUT THIS IS ALL PRETTY DISTURBING, AND ALL THE MORE REASON FOR US (MAINLY YOU) TO GET SOME MORE CREDIBLE NUMBERS OUT. BEST WISHES, TOM. > > > >