Thanks for the reference — beyond me, I’m afraid, as I’m looking for a basic signal, preferably a SW-reflecting cloud change, in the boundary layer, which might hint at a large effect from a small input, necessary if we are to put the A into AGW.

Your website, BTW, should be required reading for all policy makers, a simply-expressed, clear-eyed view of what is going on. It could usefully come with a large red Don’t Panic sign on the cover. One thing: the graph of twentieth century warming/cooling looks as if it had used a temperature series with the Folland and Parker adjustment. Without that adjustment — which our host here has convinced me is dubious at best — and using SSTs, the post WWII trend to ’76 is slightly upwards and, to me, looks as if the trend were ‘trying’ to get back to its natural .13 deg/decade slope.

However, I am not trustworthy on the F&P: I have my own reasons for wishing it to be false.

JF

Well, I take that back…we found evidence of increased precipitation efficiency associated with warming of the tropical troposphere, published August 9, 2007 in GRL:

http://www.weatherquestions.com/Spencer_07GRL.pdf

…and I am continuing this work by looking at the passive microwave signatures of precipitation systems using the AMSR-E data from NASA’s Aqua satellite (I’m the Science Team leader on that instrument). I can already report that the decrease in cirrus cloudiness with warming that we documented is also seen in the precipitation-size ice water contents of tropical thunderstorm anvils (in the 89 GHz channel of the AMSR-E). This supports the view that precipitation efficiency is tightly coupled to cirrus cloud LW feedbacks…at least in the tropics.

Everyone needs to remember that the average amount of water vapor residing in the atmosphere is not a function of the evaporation rate. It is a complex combination of processes that are connected to both the evaporation rate AND the precipitation rate.

Renno, Emanuel, and Stone:

Clouds with high precipitation efficiency produce cold and dry climates. Clouds with low precipitation efficiency lead to moist and warm climates.

Has anyone evidence of a mechanism* which might be reducing the precipitation efficiency of the global weather systems and hence be causing warming? The process seems very delicate — perhaps something is disrupting the historical Weber number of the cloud droplets. Or maybe the CCN numbers are down. If so, I’d expect relative humidity to be going up. I’m sure I’ve seen an article about anomalous pan evaporation rates in… maybe Australia.

I’ve only seen an abstract of Renno, Emanuel, and Stone.

JF
*my own candidate is obvious.

Everyone needs to remember that the average amount of water vapor residing in the atmosphere is not a function of the evaporation rate. It is a complex combination of processes that are connected to both the evaporation rate AND the precipitation rate.

Renno, Emanuel, and Stone years ago showed that by simply increasing the precipitation efficiency of precipitation systems, a cooler climate with LESS precipitation results. So, why do we never talk about the controls on precipitation efficiency?

Well, we spend so much time discussing how EVAPORATION changes with temperature, wind, etc, because we can MEASURE these things at the surface — where we live — any time we want. We see evaporation happening right before our eyes. We feel it on our skin. IN CONTRAST….the processes controlling precipitation efficiency are hidden from us, within the clouds where microphysical processes are doing their thing.

Ultimately, water vapor and cloud feedbacks are likely tightly connected to each other and to precipitation processes.

Using J. Annan’s figure of 3.7W/m2 forcing for a 1ºC tmp rise, http://www.climateaudit.org/?p=2528#comment-188894 ,
yields a 0.4(±)ºC for H2O forcing, or a 1.4ºC sensitivity (CS) figure for the Pinatubo natural experiment.

DId I get that right? Arthur Smith’s comments at 91 are noted, but I have no idea how to quantify them. Other than “the usual”

Cheers — Pete T

I agree with you thats why I moved to TN. Lower elevation Higher humidity = lower temp

Funny stuff, Mike Davis. But you’re right. I spent three summers in New Orleans. Temp hardly ever makes it to the mid 90′s. Now Phoenix is hot.

…at 60% amplification (your #80) to the 1.5 K bare CO2 effect, that would be 2.4 K warming for a doubling of CO2.

Or 1.6 to 2.2, using the “usual” range of 1 to 1.35 I’ve seen for this. Do you hae a cite for the 1.5? Odd that this is still being debated, 100+ years after Arrhenius…

Thanks for the tip on the glacier thread, which I haven’t been following. As you know, response times are under vigorous debate. In any case, it’s good to have an empirically-derived number, even if that seems squishy — see P. M. de F. Forster and M. Collins in #84, which I haven’t had time to sort out (and hoped someone else would first )

Cheers — Pete Tillman

The largest cooling in the summer of 1992 was in the center
of North America (Plate 3). As a result, the ice on Hudson
Bay melted almost a month later than normal that year. Polar
bears, who feed and have babies on the ice, were much heavier
and had more healthy cubs that summer. Biologists call
those now 11-year olds “Pinatubo Bears” [Stirling, 1997].
The cool conditions in the summer after the Pinatubo eruption
was very beneficial for the Hudson Bay polar bears, and
there were many more bears born that year than the year
before or after. The long-term concern for these bears, and
many other plants and animals in the Arctic, however, is the
opposite impact from global warming. This temporary positive
impact from Pinatubo strengthens the argument of the
negative impacts of the predicted warming. Pinatubo produced
global cooling, but impacts work in both directions, so
the benefits of Pinatubo from global cooling teach us about
the negative impacts of anthropogenic global warming.

“This temporary positive impact from Pinatubo strengthens the argument of the
negative impacts of the predicted warming…” Gee, that makes sense…

Sanctimonious twaddle. But entertaining sanctimonious twaddle

From Alan Robock, Mount Pinatubo as a Test of Climate Feedback Mechanisms
AGU Geophysical Monograph 139, 2003 — which isn’t worth your while, unless this kind of twaddle turn you on…
http://climate.envsci.rutgers.edu/pdf/VEAChapter1_Robocknew.pdf

Cheers — Pete Tillman
“Against stupidity, the Gods themselves rage in vain.”
– Friedrich von Schiller

Since increasing water vapor increases convection which increases both clouds (aka albedo) and latent heat movement from the surface, and that’s the biggest challenge, how do we even know the sign of the water vapor feedback, let alone the magnitude?