ICE wrote: > > I talked to some people around here about that, they say they had > wondered about this but not come to any conclusion: > in particular, are the mecanisms causing the spread in CS (mainly > tropical low clouds, as apparently they say in dufresne & bony 2008 > (J.of Clim)- for equilibrium CS) the same as the ones causing the > spread in "natural" variability ? > intuitevely, more variability means greater feedback loops - but it > also depends on the time-scale of these feedbacks, and... > allright - i'll keep on medidating on this...
I was googling just now on similar issues and came across some related comments from a workshop: http://books.nap.edu/openbook.php?record_id=10787&page=7 Gregory: There was logic in the expert judgment choices to exclude high sensitivity (Seq) values, since we’ve seen that the climate system doesn’t exhibit wide swings that would be characteristic of high sensitivity values. This is because the amplitude of natural variability depends on the same feedback processes that determine the value of Seq itself. also http://books.nap.edu/openbook.php?record_id=5142&page=172 If we had evidence of large natural climate excursions in the past on the 50-year time scale, there would be two possible interpretations. First, if the climate sensitivity were low, then passive internal variability and any response to global-mean external forcing would be small, so we would have to invoke either significant changes in the thermohaline circulation or (less likely on these time scales) major changes in the spatial patterns of forcing (as in the Milankovitch effect). Alternatively, if neither of the latter two mechanisms was operating, we would have to infer that the climate sensitivity was relatively large (i.e., ΔT2× in the range suggested by GCMs, 1.5°C to 4.5°C), since a large sensitivity is required for both passive internal and global-mean externally forced changes to be substantial. 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 -~----------~----~----~----~------~----~------~--~---
