date: Tue, 13 Feb 2001 14:03:27 -0500 from: "V. Ramaswamy" subject: Re: Synthesis Report (SYR): Summary for Policymakers to: Rwatson@worldbank.org, "Rajendra Pachauri" , "Tomihiro Taniguchi" , "John Houghton" , "Osvaldo Canziani" , "Bert Metz" , "Mohan Munasinghe" , "Michael Prather" , "Robert Scholes" , "John F B Mitchell" , "Thomas Stocker" , "Daniel L Albritton" , "Ulrich Cubasch" , "Stephen Schneider" , "Murari Lal" , "Zbigniew Kundzewicz" , "Barrie Pittock" , "Christopher Magadza" , "Habiba Gitay" , "T. Barker" , "J.R. Moreira" , "J.B. Robinson" , "I.A. Bashmakov" , "R.G. Richels" , "D. Zhou" , "Ian Noble" , "Narasimhan Sundararaman" , "Renate Christ" , "David Griggs" , "Neil Leary" , "Rob Swart" , "Isabel Alegre" , "Tom Karl" , "Joyce Penner" , "Bryant McAvaney" , "Bruce Hewitson" , "John Church" , "Jonathan Gregory" , "Francis Zwiers" , "Sir John Houghton" , "Joanna Haigh" , "Dr M J Salinger" , "Fons Baede" , "Fons Baede" , "Chris Folland" , "Colin Prentice" , "Colin Prentice" , "V Ramaswamy" , "Jerry Meehl" , "Filippo Giorgi" , "David Karoly" , "Linda Mearns" , "Mike Hulme" , "Berrien Moore" , "Steve Schneider" , "QK Ahmad" , "Tim Carter" , "Nigel Arnell" , "Liu Chunzhen" , "Habiba Gitay" , "Bill Easterling" , "Alla Tsyban" , "Alla Tsyban" , "Tom Wilbanks" , "Pier Vellinga" , "Tony McMichael" , "Paul Desanker" , "Murari Lal" , "Hideo Harasawa" , "Barrie Pittock" , "Martin Parry" , "Luis Mata" , "Luis Mata" , "Stewart Cohen" , "Oleg Anisimov" , "Graham Sem" , "Graham Sem" , "Barry Smit" , "Joel Smith" , "D.H. Bouille" , "J.A. Sathaye" , "J.C. Hourcade" , "K. Halsnaes" , "K. Halsnaes" , "L. Srivastava" , "R.A. Sedjo" , "T. Banuri" , "A. Markandya" , "C.J. Jepma" , "C.J. Jepma" , "F.L. Toth" , "J.P. Weyant" , "M.J. Mwandosya" , "P.E. Kauppi" , "W.R. Moomaw" , "W.R. Moomaw" , "P.R. Shukla" , "T. Morita" , "Lenny Berstein" Hi All, Re: the references to the radiative forcing aspects in Question 2 - long version, short version and SPM - of the Synthesis Report: There needs to be some care with the statements in each of the above that declares that human activities have caused a positive radiative forcing of the climate system since the preindustrial era. That may well be true, but the one important factor that constrains a bold declaration is the indirect aerosol forcing issue. Mainly because of this factor, in the WGI Chapter 6, we cautioned about a simple interpretation of the sum of the forcings for the climatic impact. A point is that the negative indirect aerosol forcing is very difficult to quantify at present. There are also some not-necessarily- minor uncertainties affecting other forcings. In the long and short documents, the point about the indirect aerosol forcing is indeed recognized by qualifying the other forcings as "identified". In the long document, a revised header is suggested: "The change in the radiative forcing of the climate system since the preindustrial era, considering the better-identified positive (warming) and negative (cooling) elements, and including both natural and anthropogenic influences, is positive (warming)." In the short document, the header could be left as is. But, in the sent. that follows: delete "significantly" - the uncertainty and the implication of a potentially large negative indirect aerosol forcing has to be recognized. For the SPM, the header could remain as is. Ram