This paper A lower and more constrained estimate of climate sensitivity using updated observations and detailed radiative forcing time series from Skeie et al is now in open peer review at Earth System Dynamics. They say an ECS of 1.84
See Figure E2 from the paper.
Abstract:
The equilibrium climate sensitivity (ECS) is constrained based on observed near-surface temperature change, changes in ocean heat content (OHC) and detailed radiative forcing (RF) time series from pre-industrial times to 2010 for all main anthropogenic and natural forcing mechanism.
The RF time series are linked to the observations of OHC and temperature change through an energy balance model and a stochastic model, using a Bayesian approach to estimate the ECS and other unknown parameters from the data. For the net anthropogenic RF the posterior mean in 2010 is 2.1 W m−2 with a 90% credible interval (C.I.) of 1.3 to 2.8 W m−2, excluding present day total aerosol effects (direct + indirect) stronger than −1.7 W m−2. The posterior mean of the ECS is 1.8 °C with 90% C.I. ranging from 0.9 to 3.2 °C which is tighter than most previously published estimates.
We find that using 3 OHC data sets simultaneously substantially narrows the range in ECS, while using only one set and similar time periods can produce comparable results as previously published estimates including the heavy tail in the probability function. The use of additional 10 yr of data for global mean temperature change and ocean heat content data narrow the probability density function of the ECS. In addition when data only until year 2000 is used the estimated mean of ECS is 20% higher. Explicitly accounting for internal variability widens the 90% C.I. for the ECS by 60%, while the mean ECS only becomes slightly higher.
h/t to Bishop Hill
Jimmy Haigh. says:
August 14, 2013 at 9:32 am
AND
Steven Mosher says:
August 14, 2013 at 9:47 am
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Jimmy, I think you mean to zero.
The longer the present temperature stasis continues, the more apparent that climate sensitivity is low and the longer it continues it will begin to approach zero.
There is reason to consider that it may be rather close to zero, eg the 1940 to 1970s cooling which more than off-set any positive climate sensitivity to the forcing of rising CO2 levels. And the present day stasis, which equals the climate sensitivity to the combined effects of long and medium term CO2 residency of CO2 emissions these past 70 years and the substantial emissions which have taken place these past 20 years with no increase in temperature. To this one must add the paleo record when there are instances of high levels of CO2 and low temperatures and rising CO2 and falling temperatures etc.
Steven is right on the more recent data and the need for more data. As this comes in, it is becoming an inescapable fact that past estimates (which were no more than guesses) were way too high. If this temperature statsis contines, even more so should temperatures fall during the next 20 years, climate sensitivity will be seen at most to be nominal.
For those interested in Climate Sensitivity and the carbon cycle there was a very good (and clear) debate on this issue in the recent article “Murry Salby responds to critics ” See:
http://wattsupwiththat.com/2013/08/11/murry-salby-responds-to-critics/#comments
This debate is well worth a read. The contributions by Bart, Richard Courtney, dbStealey, Allan MacRae, and (for the warmists) by Nick Stokes, Ferdinand Engelbeen and Nyq Only are in particular worthy of note. The debate was very clearly set out and the contributors are to be congratulated for the clarity of their response which makes it particularly easy for the reader to understand and follow the arguments being made. I highly recommend a read of this debate as it is is illuminating.
In this dabate Bart produced evidence that suggested that CO2 is driven by temperature, and the consensus view that CO2 drives temperature is not supported by the observational data. Now I do not wish to misinform what was conceded, but I gained the impression that it was accepted that temperature drives CO2 but only as far as recent response is concerned and it is a short term effect, not a long term response.
There was a debate whether there could be a different short and long term response, and whether the long term response is simply an accumulation of the short term response, but leaving that issue to one side, the effect of the concession to Bart’s evidence (see http://www.woodfortrees.org/plot/esrl-co2/derivative/mean:12/from:1979/plot/rss/from:1959/scale:0.2/offset:0.125) would seem to make it very difficult to measure climate sensitivity from short term observational data. So whilst Steven Mosher call for more data and extolls the virtue of the examination of recent data (something that I do not disagree with), it may well be the case that this data will give little insight into climate sensitivity because of the link 9at least in the short term response0 that changes in temperature drive changes in CO2 levels).
Gary, yours was a truly fine response to Mosher and a great, humorous summary of the path climate science has travelled. Well done.
Thanks! I am still reading the New Yorker’s 5 page article on the issue and I can’t help thinking about climate scientists.