[EMAIL PROTECTED] wrote:
> Why is the response to a forcing exactly, or at least to a pretty good
> approximation, linear (ie if 3.6 W/m2 cause 3 C, then it follows that
> 1.8 W/m2 will cause 1.5 C and 7.2 W/m2 will cause 6C)? Is there some
> easy to grasp explanation for that?
That's easy - everything is linear to first order :-)
Actually, perhaps one can look at the global sensitivity as some sort of
average of the local responses (not really strictly true, but still).
Over the globe there is a range of ~100C in the instantaneous (even
seasonal average) temperature and ~500W/m^2 in the incident radiation,
so the odd watt or 3 isn't really that big a deal. Even if sensitivity
was strongly nonlinear such that hot areas warmed up 10x as much as
cold ones, shifting the whole global surface by 3W or 6W would be much
closer to a linear response.
> And how does that square with so
> called tipping points?
It squares with them being "so-called" :-)
Mostly they are to do with carbon cycle feedbacks due to catastrophes
(veg or clathrates). Or else they are just hype.
> And how can a forcing be measured?
As you realised, it can't really, it is a concept based on model
experiments. (Of course solar forcing can be directly measured.)
James
--~--~---------~--~----~------------~-------~--~----~
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
-~----------~----~----~----~------~----~------~--~---
