Bishop Hill Skeie et al at ESD
Aug 14, 2013 Climate: sensitivity The Skeie et al paper, which helped kick off all the interest in low climate sensitivity when it was still in draft form, is now in open peer review at Earth System Dynamics:
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.
Apparently it was originally submitted to Journal of Climate, so presumably it had the usual rough ride there.
[Updated: I originally thought the paper was in print, but it's actually just open peer review]
Reader Comments (61)
For Martin A
Earlier I wrote this in response to a comment you made:
What you say re CS is true in a literal sense but the CS definition implies and is implied by a certain rate of increase of temp with CO2. In that sense it's continually possible to estimate its value. Of course the errors (or uncertainties as people prefer to call them) in the estimates should decrease with increased measurement time (at least if the "theory" is correct) but even if you waited for the implicit doubling time there'd still be an uncertainty.
This also answers the point you made in your most recent comment. I'm not sure how else to explain this point. CS can be measured on shorter timescales than the doubling period because it's really a test of the derivative of temperature with respect to CO2 concentration which can obviously be calculated in less than the doubling time.
But still...try this. Suppose I hypothesise that there's a logarithmic relationship between my calorie intake and my weight increase and suppose I predict that if I increase my energy intake by some amount, the same amount each day, I'm going to double my weight in 6 months. Would I have to wait 6 months to test the predicted relationship between my weight and calorie intake? (I shall have another chocolate while I think about that.)
For Martin A
In my efforts to understand the oddly strong tone of your disagreement with my perfectly reasonable points, I've just noticed you've been talking about CS "predictions" while I've been talking about calculated CS. If you really meant "predictions" then I agree with you as just how the future calculated value of CS will go is anyone's guess (although tending zero-wards might be a reasonable extrapolation of the recent trend in the calculations).
richard verney
Not all deep water temperature changes take place over long timescales.
Consider ENSO. La Nina conditions reduce global temperature by bringing cool deep ocean water to the surface, which absorbs more heat. This warmer water is then recycled downwards into deeper levels. When the pattern changes to El Nino the warmer water returns to the surface. The Pacific Ocean becomes a net heat releaser and global temperatures rise.
The timescale is measured in years, not millennia.
Why do you persist in referring to "alleged" warming when observational evidence is available?
http://onlinelibrary.wiley.com/doi/10.1002/grl.50382/full
Regarding effects of warmer water returning to the surface, you do not need a large change. Consider the effect of thermohaline water surfacing off Antarctica at 5C rather than 4C. That would be a significant change in the heat budget for the region.
Aug 15, 2013 at 10:17 PM | Entropic Man
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Inadvertently, you prove my point. You say:
"Consider ENSO. La Nina conditions reduce global temperature by bringing cool deep ocean water to the surface..."
The bringing up (ie., the return of) water from the deep (ie., the ocean below say 700m - I use this figure since it is alleged that it is water below this depth that is gettting warmer), cools global temperatures no matter whether the deep ocean is say 3degC or 3.001degC, or 3.002 degC' or even 3.01 degC or 3.03degC etc..
It has to since this water is only a few degrees C, whereas surface temps are not less than about 15 deg C globally (in the Pacific areas/ Tropical Sea areas they are far higher).
It does not matter that the brought up water further warms and then goes back down to the deep. If this causes the deep ocean to get warmer still by say a thousandth of a degree, or even by a hundredth of a degree, the next time the deep ocean returns to the surface, it will again cool down the surface layer because it is still so much cooler than the top ocean temperature, and accordingly the result of this is that it will reduce global temperatures.
Any extra heat in the deep ocean cannot harm us on any reasonable time scale. We will be in another ice age before it resurfaces to any significant degree. There can be no further worries if the effect of increasing CO2 emissions and AGW is to merely put some additional heat in the deep ocean. The scare is over.
Dung, Simon Anthony, and Martin A
In all these discussions, and looking at recent temperature data with a view to refining an assessment of Climate Sensitivity (if indeed there is such a concept), one frequently overlooks the observational data considered by Miskolczi and his theory of the saturated GHE.
Miskolczi studied the absorption of IR by the atmosphere (utilising data from weather balloon observations) and he found that the absorption of IR had remained constant (or nearly constant) for the past 60 years, or so!!
During this period, CO2 levels haved increased by more than 20%, and yet this has not resulted in a corresponding increase in IR absorption! To the contrary, IR absorption has remained constant thereby suggesting that the GHE is fully saturated by the time CO2 levels are in the region of about 320ppm
This research therefore suggests that if there were to be yet further increase in CO2 levels, there will be no further increase in IR absorption, and without such an increase, there is in fact no further on going GHE and thus Cliamte Sensitivity (to a further doubling) must be approximately zero.
The full effect of this import research is not being fully considered and has not been given sufficient account when people endeavour to assess Climate sensitivity, and put a figure on it.
I wonder how this paper stands up to the fact that globally temperature equilibrium is never attained? Since this planet revolve on its axis it is continually warming and cooling as one face moves from day to night. But of course this salient fact is ignored by the GHE alatmists.
As the satellite and balloon data has shown no temperature increase for 16 years for the increase in carbon dioxide concentrations, surely the ECS is zero for this range ?
John Marshall
I think the idea of climate sensitivity is nonsense for a number of reasons.
But I don't think that the fact that there is a daily warming/cooling cycle invalidates the idea of the climate eventually reaching an equilbrium - it would be what time series analysts refer to as "cyclo-stationary" ie when in equilibrium, the statistics vary periodically but do not change otherwise.
Since (according to climate science) it would take centuries for the equilibrium to be reached after a step change of atmospheric CO2, small changes with a 24 hour period would not affect the picture when looked at with a time resolution of years or decades.
But, as I said, I think the whole thing is nonsensical for other reasons - even the idea that the climate response is a single-valued function seems questionable to me.
Richard Verney
You are mistaken to think that heat returning from the deep ocean is irrelevant because it may be cooler than the warmest global temperature. The key question is "Is it warmer than the region in which it emerges, thus increasing the local temperature?"
Have you links to Miskolczi's original papers? This is the first I've heard of him. I'm sure you'll understand that I'd prefer to read his own words, unspun by some spin-sceptic website.
I think you are grasping at straws Entropic Man, because, first off, if the ocean is much colder than atmospheric temps over most of the globe, which it obviously is, then whatever temperature rise occurring at small local areas where this might not be true would be overwhelmed on average.
I thought the discussion in general was about global warming, not local warming. Kindly refrain from trying to move the pea.
tomdesabla
Just following the evidence. Even Andrew Monford agrees with me. In his evidence to Parliament he ascribed the warming of the Arctic to warm ocean currents.