A new paper published in Ecological Modelling finds climate sensitivity to doubled CO2 concentrations is significantly lower than estimates from the IPCC and climate models which “utilize uncertain historical data and make various assumptions about forcings.” The author instead uses a ‘minimal model’ with the fewest possible assumptions and least data uncertainty to derive a transient climate sensitivity of only 1.093C:
“A minimal model was used that has the fewest possible assumptions and the least data uncertainty. Using only the historical surface temperature record, the periodic temperature oscillations often associated with the Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation were estimated and subtracted from the surface temperature data, leaving a linear warming trend identified as an anthropogenic signal. This estimated rate of warming was related to the fraction of a log CO2 doubling from 1959 to 2013 to give an estimated transient sensitivity of 1.093 °C (0.96–1.23 °C 95% confidence limits) and equilibrium climate sensitivity of 1.99 °C (1.75–2.23 °C). It is argued that higher estimates derived from climate models are incorrect because they disagree with empirical estimates.”
Otto et al find equilibrium climate sensitivity [over the next several centuries] is only ~1.3 times greater than transient climate sensitivity, thus the estimate of 1.093C transient sensitivity could be associated with as little as 1.4C equilibrium sensitivity, less than half of the implied IPCC central estimate in AR5 of ~3.3C.
Moreover, this paper does not assume any solar forcing or solar amplification mechanisms. The integral of solar activity plus ocean oscillations explain ~95% of global temperature change over the past 400 years. Including potential solar forcing into the ‘minimal model’ could substantially reduce estimated climate sensitivity to CO2 to a much greater extent.
- Empirical estimates of climate sensitivity are highly uncertain.
- Anthropogenic warming was estimated by signal decomposition.
- Warming and forcing were equated in the time domain to obtain sensitivity.
- Estimated sensitivity is 1.093 °C (transient) and 1.99 °C (equilibrium).
- Empirical study sensitivity estimates fall below those based on GCMs [Global Circulation Models].
Abstract
Climate sensitivity summarizes the net effect of a change in forcing on Earth’s surface temperature. Estimates based on energy balance calculations give generally lower values for sensitivity (< 2 °C per doubling of forcing) than those based on general circulation models, but utilize uncertain historical data and make various assumptions about forcings. A minimal model was used that has the fewest possible assumptions and the least data uncertainty. Using only the historical surface temperature record, the periodic temperature oscillations often associated with the Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation were estimated and subtracted from the surface temperature data, leaving a linear warming trend identified as an anthropogenic signal. This estimated rate of warming was related to the fraction of a log CO2 doubling from 1959 to 2013 to give an estimated transient sensitivity of 1.093 °C (0.96–1.23 °C 95% confidence limits) and equilibrium climate sensitivity of 1.99 °C (1.75–2.23 °C). It is argued that higher estimates derived from climate models are incorrect because they disagree with empirical estimates.
mpainter says:
July 25, 2014 at 9:55 am
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Because, that alone does not establish that CO2 is the driver of temperatures..
It would be possible that something, other than CO2, could be driving temperatures up. As a consequence of the warmer temperatures (which were not driven up by CO2), more CO2 is out gassed thereby increasing the concentration of CO2 in the atmosphere.. So you can have correlation, but correlation is not causation.
AGW is presently just conjecture. Of course, that does not mean that it does not exist, and is not real. It may be real.
As you say, the fact that temperatures are not increasing runs contrary to the ‘theory’ (conjecture), but the problem is the accuracy of the data sets, and whether there is an AGW signal in those data sets, albeit weaker than the error bands of the data sets that we are using.
See more generally my recent posts above.
HenryP says:
July 25, 2014 at 7:02 am
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Henry
I like all the work that you have done with the compilation of your tables. I consider that you are right to look at both maxima and minima seperately. I hate averages, since it disguises the detail, and the devil lies in the detail. It has always surprised me that there is not much more detailed analysis of max/min temperatures seperately, analysis of seasonal data etc etc.
I myself do not consider a few tenths of a degree to be climate change. So what are we saying that is climate change, eg., generally the nights are a little bit warmer, Spring starts a couple of days earlier, Autumn starts a couple of days later, winters are less harsh, high latitues are warmer but the tropics are not etc. etc. If one is discussing climate change, I would expect to see a detailed analysis iofthe ways in which climate (not temperature) is changing. Strange that we do not see that kind of approach, but then again, ikt would demonstarte that climate is local/regional, not global and would be more difficult to run ‘we are all in it together’ argument..
That said, for reasons detailed in my post at 3:50 am, I think that you are overplaying your hand. If for no other reason than the real issue, is energy imbalance, and looking at temperatures (other than sea temperature) is not measuring the required metric, and that dbstealey is right to not go quite as far as you go. But it appears to me that the difference between you is so small, so there appears nothing in substance in the argument and the allegations of fence sitting.
At some stage the science will come out, and people will be able to firm up their views. Presently, the data sets are so poor, with wide error bands, and not fit for the purpose that they are being put, people are over extrapolating the data etc such that, in my opinion, no fiirm conclusion can rightly be reached, at this stage. Time will tell whether you are right.
Continue your good work. I check you pool table from time to time, and no doubt many others do as well.
@richard
Thanks. The drop in global temp. is now about -0.2K since 2000 according to my own data set (means).
It does not look like a lot, agreed. My wife also still laughs at me worrying about it.
However, clearly the graphs are still pointing to more that is coming up. We are cooling from the top latitudes down,
e.g. like I said
Alaska is already down -1.0K down since 1998.
However, a small change may add up to more, e.g. -0.2K means more cloud formation at lower latitudes, and less clouds at the higher latitudes (droughts) ,then more clouds at lower latitudes mean more cooling, etc. etc. We spiral down.
All of this while everybody is scrambling to explain the pause, using useless data sets that are not [even] properly balanced.
My results in the tables have revealed to me where we we are in the 87 year Gleissberg cycle,
http://www.nonlin-processes-geophys.net/17/585/2010/npg-17-585-2010.html
[I am not yet sure from my own results where we are in the De Vries cycle]
According to my various calculations, comparatively speaking, we are now in ca. 1925.
Note that the Dust Bowl drought 1932-1939 was one of the worst environmental disasters of the Twentieth Century anywhere in the world. Three million people left their farms on the Great Plains during the drought and half a million migrated to other states, almost all to the West. http://www.ldeo.columbia.edu/res/div/ocp/drought/dust_storms.shtml
I find that as we are moving back, up, from the deep end of the 87 year sine wave, there will be standstill in the change of the speed of cooling, neither accelerating nor decelerating, on the bottom of the wave; therefore naturally, there will also be a lull in pressure difference at that > [40 latitude], where the Dust Bowl drought took place, meaning: less weather (read: rain). As stated before, according to my calculations, this will start around 2020 or 2021…..i.e. 1927=2016 (projected, by myself and the planets…)> add 5 years and we are in 2021.
Danger from global cooling is documented and provable. It looks we have only ca. 7 “fat” years left……
WHAT MUST WE DO?
We urgently need to develop and encourage more agriculture at lower latitudes, like in Africa and/or South America. This is where we can expect to find warmth and more rain during a global cooling period.
We need to warn the farmers living at the higher latitudes (>40) who already suffered poor crops due to the droughts that things are not going to get better there for the next few decades. It will only get worse as time goes by.
We also have to provide more protection against more precipitation at certain places of lower latitudes (FLOODS!), <[30] latitude, especially around the equator.
MPainter says:
I do not understand why AGW would not qualify as a hypothesis. It puts warming attributable to increasing atm CO2 and predicts increasing temperatures with increasing CO2. This has not happened and thus the Hypothesis stands refuted by the data, it seems.
That is my point. To be elevated from a conjecture to a hypothesis, the CO2=AGW claim must be able to make repeated, accurate predictions. CO2=AGW does not. For example, as CO2 continues to rise, global T does not follow, which was predicted incessantly by the alarmist crowd [until global warming stopped].
Next, if you want to call AGW a hypothesis, that’s OK. But a conjecture is not wrong per se. A conjecture is the starting point of the scientific method [Conjecture, Hypothesis, Theory, Law]. For myself, until/unless I have testable measurements quantifying the fraction of a degree of global warming attributable to human CO2 emissions, I will consider AGW to be a conjecture.; an unproven supposition.
Some folks, like the ‘Slayers’, claim that the Greenhouse Effect doesn’t exist, and there are those who say it is all due to the Sun. There are others who say it is all due to natural cycles. At this point, we just do not know. But I personally don’t see any evidence that anthropogenic CO2 causes any measurable global warming, because there are no such measurements. Many people have been searching for AGW measurements for more than 30 years, but with no success at all.
I certainly don’t know what drives global climate changes. But I want to know. If the answer turns out to be CO2, then I will accept that — so long as it is proven with testrable measurements. Because the goal is scientific knowledge, not being part of a ‘consensus’.