Dear Stuart: The issue is a bit more complicated than Ken indicates:
1. Radiative forcing is measured (well, actually calculated) for the tropopause. It does make a difference in the response the degree to which the resulting forcing results in a change in the surface relative to the tropospheric energy balance, especially for the hydrological cycle influence. 2. The geographic pattern also matters, though perhaps not for the short term. But if one has all the forcing in the Northern Hemisphere versus Southern, one will get a different response due to the land/ocean difference, etc. (this was the case for example during mid-20th century when sulfate forcing in NH led to a slowing of warming or even a cooling, but did not do so in the SH). Also, the orbital changes that drive the ice age cycling actually create (independent of changes at the surface) virtually no annual global forcing‹all they do is redistribute energy by season and latitude, so for that case, a zero forcing is causing ice age cycling (through a lot of feedbacks, etc.). 3. There is also the issue of how long the forcing persists‹short time ones like volcanic eruptions have a large forcing, but due to short time they are aloft, the response does not reach equilibrium and eventually goes away. A small, persistent change can, however, have a longer term effect as it activates some of the longer term feedback processes. And I am sure there are further nuances. Mike MacCracken On 12/31/08 2:29 PM, "Ken Caldeira" <[email protected]> wrote: > You can of course add radiative forcing "linearly". (What other kind of > addition is there?) > > An important question is whether climate response to the sum of radiative > forcings is the same as the sum of the climate responses to individual > radiative forcings. > > The answer to this question depends on the size of the perturbation and your > tolerance for approximation. > > Recall the maxim: "To first order, everything is linear !!" > > ( More strictly speaking, "To first order, differentiable functions are > linear." ) > > > > On Wed, Dec 31, 2008 at 11:13 AM, Stuart Strand <[email protected]> > wrote: >> >> Is radiative forcing additive linearly? >> >> = Stuart = >> >> Stuart E. Strand >> 167 Wilcox Hall, Box 352700, Univ. Washington, Seattle, WA 98195 >> voice 206-543-5350, fax 206-685-3836 >> http://faculty.washington.edu/sstrand/ >> >> Using only muscle power, who is the fastest person in the world? >> Flying start, 200 m: 82.3 mph! http://en.wikipedia.org/wiki/Sam_Whittingham >> Hour http://en.wikipedia.org/wiki/Hour_record >> 55 miles, upside down, backwards, and head first! >> >> >> > > > > > --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
