This accepted sensitivity doesn't take into account feedback effects, as far as I know. There can be no stable sensitivity to a non-linear response - least of all a step change, which we may soon be facing as we spiral all the way out of the ice-age into a 'hothouse earth' state.
When you take into account the lag in the system (perhaps 40 years), precautionary-principle estimates of sensitivity and non-linearities, it seems that the 2C limit exists mainly in the minds of politicians, not scientists. A 2009/9/22 Mike MacCracken <[email protected]>: > Interesting. > > So, 2 C above preindustrial is the official goal by the leaders. We have > warmed by 0.8 C, so that means we have about 1.2 C to go. Convert that by > multiplying by 1.8, and that gives a bit over 2 F to go from present > warming. I guess the larger number makes people think we have a bit more > room available. > > Only trouble is, of course, that given present GHG concentrations in absence > of the SO2 cooling offset that would go away virtually immediately if we > stopped emissions from coal-fired plants, we would be at forcing of about > 2.7 W/m2 (so 1.6 net that IPCC gives plus 1.1 for aerosol forcing), and if > climate sensitivity is 0.75 C per W/m2 (and it may be higher, or maybe > lower), that gives an equilibrium warming of 2 C (though, of course, if all > emissions stopped, there would be a downward drift—but if we hold that > forcing constant, we are at 2 C plus or minus. > > Best, Mike > > > > > On 9/20/09 9:39 PM, "Manu Sharma" <[email protected]> wrote: > > From the NYT article linked below: > > Fundamentally, although limiting the temperature rise to 2 degrees > Fahrenheit is an accepted goal, there is no consensus on how to get there. > This 2-degree Fahrenheit rise is the equivalent of the original goal of 2 > degrees Celsius above the planet’s temperature just before the Industrial > Revolution. > > ??????? > > How did this go past the editors at The New York Times? > > - Manu > > On Sun, Sep 20, 2009 at 4:28 PM, <[email protected]> wrote: > > <http://www.nytimes.com/> > <http://www.nytimes.com/adx/bin/adx_click.html?type=goto&opzn&page=www.nytimes.com/yr/mo/day/science/earth&pos=TopRight-EmailThis&sn2=65192d3/561f2559&sn1=dcb1d65c/835343f3&camp=foxsearch2009_emailtools_1011077b_nyt5&ad=Adam_88x31_b_nowplaying&goto=http%3A%2F%2Fwww%2Efoxsearchlight%2Ecom%2FAdam> > This page was sent to you by: [email protected] Message from sender: > more cheerful stuff Peter > > SCIENCE / ENVIRONMENT | September 20, 2009 > No Climate Change Leader as Nations Prepare to Meet > <http://www.nytimes.com/2009/09/20/science/earth/20nations.html?emc=eta1> > By NEIL MacFARQUHAR > As nations gather for a major summit meeting on climate change, none want to > take the lead in fighting for significant international targets. > > Advertisement > > Amelia stars two-time Academy Award winner Hilary Swank as Amelia Earhart, > the legendary aviatrix. Directed by Mira Nair. > > Click here to view trailer > <http://www.nytimes.com/adx/bin/adx_click.html?type=goto&opzn&page=www.nytimes.com/yr/mo/day/science/earth&pos=Center1&sn2=48422044/176b9274&sn1=caf97136/2ae70fcf&camp=foxsearch2009_emailtools_1011077g-nyt5&ad=amelia_g_120x60&goto=http://www.foxsearchlight.com/amelia> > <http://www.nytimes.com/adx/bin/adx_click.html?type=goto&opzn&page=www.nytimes.com/yr/mo/day/science/earth&pos=Center1&sn2=48422044/176b9274&sn1=caf97136/2ae70fcf&camp=foxsearch2009_emailtools_1011077g-nyt5&ad=amelia_g_120x60&goto=http://www.foxsearchlight.com/amelia> > > Copyright 2009 > <http://www.nytimes.com/ref/membercenter/help/copyright.html> The New York > Times Company <http://www.nytco.com/> | Privacy Policy > <http://www.nytimes.com/ref/membercenter/help/privacy.html> > > > > > > > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. 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/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
