«Observational Constraints on Mixed - Phase Clouds
Imply Higher Climate Sensitivity.»
There could also be tipping points, which would
imply a high climate sensitivity.
Gavin's refusal to admit the extreme LU efficacy comes down to accepting one very dubious run, a run which is a clear statistical outlier, goes to the heart of the problem with Marvel et al: the authors got results they «liked» (lower efficacy for many forcings
implies higher climate sensitivity... casting doubt on lower empirical estimates), and so failed to critically examine if their results might have errors.
Conversely a low forcing giving rise to the same observed temperature gain
implies a high climate sensitivity.
Not exact matches
The need for prompt (urgent) action
implied by these realities may not be a surprise to the relevant scientific community, because paleoclimate data revealed
high climate sensitivity and the dominance of amplifying feedbacks.
The low
sensitivity you quote is just as incredible as the
high numbers discussed above (think about what it would
imply for the glacial
climate).
This seems to
imply the water vapor feedback gets stronger at
higher temperatures so that the
climate sensitivity does not decrease.
Conversely, if «
climate sensitivity» for a doubling of CO2 is based on recent measurements and CO rates, and past natural variability is underestimated — as you've shown here — then this
implies our estimates of
sensitivity per CO2 doubling is too
high, not too low.
«We can rule out very low
climate sensitivities that might
imply you don't need to do very much at all but also very
high climate sensitivities that would be very difficult to adapt to.
I think James» point about the last decade is not that global warming has stopped (
implying low or zero
climate sensitivity) but that it has not accelerated to the extent that it would have if
climate sensitivity were very
high (above, say, 4).
The problem catastrophists have with defending their
higher climate sensitivities is that these
sensitivities imply that we should have seen much more warming over the past 100 years, as much as 1.5 C or more instead of about 0.6 C.
The fact remains that the IPCC report altered the conclusions of the original paper, and in a direction to
imply a
higher and more alarming
climate sensitivity, without giving the original results or explaining clearly what they'd done to alter them.
Which would, of course,
imply an absurdly
high effective
climate sensitivity.
BBD wrote: «
Implying or stating that the slow - down in warming is evidence that AGW is «refuted» or the more nuanced version that it shows that the
climate sensitivity estimate is too
high is misrepresentation.»
Implying or stating that the slow - down in warming is evidence that AGW is «refuted» or the more nuanced version that it shows that the
climate sensitivity estimate is too
high is misrepresentation.
This
implies that the
climate sensitivity (the temperature increase with a doubling of atmospheric CO2 concentration) is at the
higher end of the range of estimates.
The impression I've gotten is that some people, not knowing that «net positive feedback» may exclude the Planck response, think that this must
imply the
climate is unstable — the funny thing is, this will be used to argue for a lower
climate sensitivity, but one could see that something is wrong here because the
higher climate sensitivity caused by the positive feedback is still finite.
(Note that the 2C
climate sensitivity this result
implies doesn't allow for any forcings other than CO2, so it will be too
high).
Interestingly enough with regards to LC09, aside from the errors discussed above, there was a paper by Forester & Gregory published in 2006 that also analyzed the ERBE data and came to the exact opposite conclusion — a positive feedback factor of around 2.3 Wm - 2 / K,
implying a
climate sensitivity higher than the IPCC.