2011-01-21 02:22:36new paper on albedo
Robert Way

2011-01-21 03:11:07
Mark Richardson



I'm going to email one of the authors about the long term response, since I think short term calculations of it might be an overestimate.


For example, half of their figure comes from summer decline in Arctic sea ice. Which has declined much more rapidly than climate models had predicted by this point, but we've already lost half of it with only 0.7 C warming. There won't be more to lose after ~1.5 C warming so it won't contribute to the rest of the climate sensitivity!

At least, that's what I think I understand.

2011-01-21 03:19:49
Mark Richardson

If the figure really is higher, then OUCH.



It might be worth doing a post on the cumulative effect of feedbacks.

For those that haven't looked at this before, the equation is something like RF / (sum of feedbacks; where positive ones have negative sign), so for CO2 doubling of 3.7 W m^-2 you get about 1.1 C warming based on the blackbody feedback of 3.3 from atmospheric and surface emissivity.

If water vapour + lapse rate is -1.5 W m^-2 K^-1 then  that takes you to 3.3-1.5 = 1.8, i.e. sensitivity now 3.7/1.8 = 2 C.


If snow is the 0.2 average from models, then you're at 3.7/1.6 =  2.3 C.

 i.e. it adds about 0.25 C warming, but if it acted on its own with no water vapour you'd go from 1.1C to (3.7/3.1) = 1.2 C or 0.1 C bonus warming from snow. i.e. because of 'recycling' of the trapped heat by water vapour, snow has more of an impact.




However, if it's in the middle of their range at 0.7, then climate sensitivity assuming neutral cloud effects (and recent measurements say they're positive) is an immense 4.1 C!

2011-01-21 06:30:02free copy?
Dana Nuccitelli

I'd like to include a bit on this study in the Monckton Myths #7 post.  Can somebody hook me up with a free copy?


*update* Albatross got me the paper.  I won't be able to cover it in great depth though, so Mark's idea of a cumulative feedback post is a good one.

By the way Mark, if you've got 1.5 Wm-2K-1 from water vapor + lapse rate, and 0.7 from snow/ice, that's a 3.4°C sensitivity (assuming zero for clouds).  I think you subtracted 0.2 and then 0.7 to get the 4.1°C.  But the 0.2 and 0.7 are different estimates of the same snow/ice effect.

2011-01-21 21:21:58
Mark Richardson
Oops, my bad. :embarrassed: