----- Original Message ----- From: "James Annan" <[EMAIL PROTECTED]> Newsgroups: gmane.science.general.global-change To: <[email protected]> Sent: Friday, January 25, 2008 4:41 PM Subject: [Global Change: 2395] Re: Is it true?
> > Don Libby wrote: >> ----- Original Message ----- >> From: "Tom Adams" <[EMAIL PROTECTED]> >> Newsgroups: gmane.science.general.global-change >> To: "globalchange" <[email protected]> >> Sent: Monday, January 21, 2008 2:25 PM >> Subject: [Global Change: 2386] Re: Is it true? >> >> On Jan 18, 5:55 pm, James Annan <[EMAIL PROTECTED]> wrote: >>> Don Libby wrote: >>>> Today I read a statement in the popular press that strikes me as >>>> absurd, >>>> but >>>> is it true? >>>> "The world must reduce carbon emissions by 90% by 2030 to avert an >>>> ecosystem >>>> collapse..." >>> This is probably based on the +2C "dangerous climate change": it is true >>> enough if you equate (the *risk* of) dangerous climate change with "an >>> ecosystem collapse". >>> >> >> Since this contrasts sharply with the opinion I had formed that shallow >> cuts >> now and deeper cuts later in the Century would be adequate to stabilize >> at >> or near 2x pre-industrial by 2100 (for example, the IS92c emission >> trajectory), I thought that perhaps some new science had cropped up in >> the >> last five years that escaped my attention and required me to get busy >> with >> my homework. > > I think you may be missing a subtle point here. +2C (relative to > pre-industrial) requires stabilisation in the region of 450ppm CO2, not > 550ppm (which is doubling). Of course there is uncertainty due to > uncertainty in climate sensitivity, but these are probably reasonable > ballpark figures. Given that we are at 430ppm CO2 equivalent, and 380ppm > CO2 alone (and rapidly rising), the lower target is pretty hard! > > James > Good point - that would require more cuts sooner - but how much more, how much sooner and at what cost are still debateable. I like the pragmatic approach of the McKinsey report, which catalogues the cost and emission reduction potential of 250 possible actions (for the US) to arrive at a potential reduction of 3.0-4.5 GtCO2-equivalent by 2030 (roughly 30%-45% below projected BAU; 42%-63% below 2005; 48%-72% below 1990 levels) at almost no net cost to society (cost savings from efficiency measures nearly offsets cost expenditures for capital intensive infrastructure construction projects.) http://www.mckinsey.com/clientservice/ccsi/greenhousegas.asp So if we can (with a coordinated effort) get to 50% below 2005 levels by 2030, the other 40% (taking Stern and Monbiot at their words that 90% is the magic number) will have to come either after 2030, or from outside the US (importing carbon credits as Tom Adams mentioned). Under the circumstances, it would be a good idea to set up a global carbon credit market, rather than the limited regional "bubbles" called for in the Kyoto protocol. I haven't paid much attention to the results of the UNFCCC meeting in Bali - was global cap and trade still on the table at the end of the day? -dl --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
