By Patrick J. Michaels and Paul C. “Chip” Knappenberger
We have two new entries to the long (and growing) list of papers appearing the in recent scientific literature that argue that the earth’s climate sensitivity—the ultimate rise in the earth’s average surface temperature from a doubling of the atmospheric carbon dioxide content—is close to 2°C, or near the low end of the range of possible values presented by the U.N.’s Intergovernmental Panel on Climate Change (IPCC). With a low-end warming comes low-end impacts and an overall lack of urgency for federal rules and regulations (such as those outlined in the President’s Climate Action Plan) to limit carbon dioxide emissions and limit our energy choices.
The first is the result of a research effort conducted by Craig Loehle and published in the journal Ecological Modelling. The paper is a pretty straightforward determination of the climate sensitivity. Loehle first uses a model of natural modulations to remove the influence of natural variability (such as solar activity and ocean circulation cycles) from the observed temperature history since 1850. The linear trend in the post-1950 residuals from Loehle’s natural variability model was then assumed to be largely the result, in net, of human carbon dioxide emissions. By dividing the total temperature change (as indicated by the best-fit linear trend) by the observed rise in atmospheric carbon dioxide content, and then applying that relationship to a doubling of the carbon dioxide content, Loehle arrives at an estimate of the earth’s transient climate sensitivity—transient, in the sense that at the time of CO2 doubling, the earth has yet to reach a state of equilibrium and some warming is still to come.
Loehle estimated the equilibrium climate sensitivity from his transient calculation based on the average transient:equilibrium ratio projected by the collection of climate models used in the IPCC’s most recent Assessment Report. In doing so, he arrived at an equilibrium climate sensitivity estimate of 1.99°C with a 95% confidence range of it being between 1.75°C and 2.23°C.
Compare Loehle’s estimate to the IPCC’s latest assessment of the earth’s equilibrium climate sensitivity which assigns a 66 percent or greater likelihood that it lies somewhere in the range from 1.5°C to 4.5°C. Loehle’s determination is more precise and decidedly towards the low end of the range.
The second entry to our list of low climate sensitivity estimates comes from Roy Spencer and William Braswell and published in the Asia-Pacific Journal of Atmospheric Sciences. Spencer and Braswell used a very simple climate model to simulate the global temperature variations averaged over the top 2000 meters of the global ocean during the period 1955-2011. They first ran the simulation using only volcanic and anthropogenic influences on the climate. They ran the simulation again adding a simple take on the natural variability contributed by the El Niño/La Niña process. And they ran the simulation a final time adding in a more complex situation involving a feedback from El Niño/La Niña onto natural cloud characteristics. They then compared their model results with the set of real-world observations.
What the found, was the that the complex situation involving El Niño/La Niña feedbacks onto cloud properties produced the best match to the observations. And this situation also produced the lowest estimate for the earth’s climate sensitivity to carbon dioxide emissions—a value of 1.3°C.
Spencer and Braswell freely admit that using their simple model is just the first step in a complicated diagnosis, but also point out that the results from simple models provide insight that should help guide the development of more complex models, and ultimately could help unravel some of the mystery as to why full climate models produce high estimates of the earth’s equilibrium climate sensitivity, while estimates based in real-world observations are much lower.
Our Figure below helps to illustrate the discrepancy between climate model estimates and real-world estimates of the earth’s equilibrium climate sensitivity. It shows Loehle’s determination as well as that of Spencer and Braswell along with 16 other estimates reported in the scientific literature, beginning in 2011. Also included in our Figure is both the IPCC’s latest assessment of the literature as well as the characteristics of the equilibrium climate sensitivity from the collection of climate models that the IPCC uses to base its impacts assessment.
Figure 1. Climate sensitivity estimates from new research beginning in 2011 (colored), compared with the assessed range given in the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) and the collection of climate models used in the IPCC AR5. The “likely” (greater than a 66% likelihood of occurrence)range in the IPCC Assessment is indicated by the gray bar. The arrows indicate the 5 to 95 percent confidence bounds for each estimate along with the best estimate (median of each probability density function; or the mean of multiple estimates; colored vertical line). Ring et al. (2012) present four estimates of the climate sensitivity and the red box encompasses those estimates. The right-hand side of the IPCC AR5 range is actually the 90% upper bound (the IPCC does not actually state the value for the upper 95 percent confidence bound of their estimate). Spencer and Braswell (2013) produce a single ECS value best-matched to ocean heat content observations and internal radiative forcing.
Quite obviously, the IPCC is rapidly losing is credibility.
As a result, the Obama Administration would do better to come to grips with this fact and stop deferring to the IPCC findings when trying to justify increasingly burdensome federal regulation of carbon dioxide emissions, with the combined effects of manipulating markets and restricting energy choices.
References:
Loehle, C., 2014. A minimal model for estimating climate sensitivity. Ecological Modelling, 276, 80-84.
Spencer, R.W., and W. D. Braswell, 2013. The role of ENSO in global ocean temperature changes during 1955-2011 simulated with a 1D climate model. Asia-Pacific Journal of Atmospheric Sciences, doi:10.1007/s13143-014-0011-z.
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Global Science Report is a feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”
strike says:
March 1, 2014 at 1:34 am
@PMHinSC “Perhaps the more relevant concern is whether warming will do more good than harm. Particularly since at the current rate we have over a century and a half before CO2 doubles.
“If that is Your argument, our beloved warmists will say, maybe you’re right for 2 degrees, but what if 4 or 6 degrees bla,bla bla and then You are in the defense. If you argument with this “even-if the temperature”, this “even-if” will not be heard and for them and for neutral listeners you already“
“What if” is a game not an argument.
Arguing that sensitivity should be the primary focus is getting the cart before the horse. Someone should have to demonstrate that warming does more harm than good before sensitivity become the primary focus of discussion.
“. If the direct effect per doubling is agreed to be 1.0°C to 1.2°C, then the sensitivity is 0.26°C to 0.31°C per doubling after accounting for feedbacks…”
Michael D. Smith,
Do you mean that feedbacks add an additional 0.26 – 0.31 C to the 1.0 – 1.2 C, or are you claiming that feedbacks are negative, giving a total of 0.26 – 0.31 C? If the latter, you’ve run off the rails. If the former, I think you are standing on solid ground. A number of years back, before the pause was clearly a pause, I estimated the equilibrium sensitivity at 1.4 +- 0.2 C based on historical data over the last century. Your result, if you mean the former interpretation, seems reasonable to me.
Someone replied to one of my comments on a blog that their professor stated the is ONLY man made CO2 … then went on with how the other “Natural” CO2 was not harmful. HOW? What is different IR wise about man made CO2?
It’s not quite like that. Look at the atmosphere like a bathtub with a couple of drains on the bottom. but what is circulated out is circulated back in (at a slight CO2 loss). When man adds CO2 to the bathtub, the level of CO2 in the bathtub goes up, too. (More drains out, as well.)
CO2 content has been increasing at ~0.4% per year. Now, I don’t think that matters much, but still, we are adding the CO2.
evanmjones says:
March 1, 2014 at 7:33 pm
I am sorry Evan. Analyzing your post in detail is a little confusing. Please explain.
Frederick Colbourne writes regarding sensitivity .. ..
Actually the physics tells us that the logarithm of CO2 is the relevant variable.
No valid physics tells us there is any warming sensitivity to carbon dioxide. Valid physics tells us that a planet’s troposphere spontaneously evolves towards a state of maximum entropy, that state being thus characterised by isentropic conditions and hence displaying an autonomous thermal gradient which results from the force of gravity acting on individual molecules in free flight between collisions, wherein kinetic energy exchanges with gravitational potential energy..
So the thermal gradient exists and is obviously caused by this process on other planets where there may be no surface, no direct solar radiation and no upward rising gases. So too on Earth, and hence there is no warming by 33 degrees or whatever due to sensitivity to water vapor and radiating gases. If water vapor were raising temperatures by most of that 33 degrees, then moist rain forest regions would be perhaps 15 to 20 degrees warmer than dry deserts, and they are not.
So the whole postulalte of positive sensitivity is false, and in fact water vapor lowers surface temperatures because it reduces the thermal gradient by inter-molecular radiation.
Jim Cripwell says:
February 28, 2014 at 10:43 am
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I have been saying similar for years. I find the entire discussions about climate sensitivity disingenuous. Until such time as we can separate the signal from CO2 from the noise of natural variation, factually, it is impossible, from observational data, to extrapolate a figure for climate sensitivity. And without basing the figure on underlying data, any model projection is nothing more than fantasy.
The stark fact is this; there is no first order correlation between CO2 and temperature in any of the instrument temperature records, such that presently we are unable to detect any temperature signal to increases in CO2 within the present and existing limitations of our best measuring equipment.
As far as the satellite era is concerned, the satellite data suggests, over a 33/34 year period, that temperatures have not significantly increased at all due to any increase in atmospheric levels of CO2, ie., temperatures have been essentially flat between inception in 1979 to around before the super El Nino of 1998, and once again following that event, essentially flat to date. There has simply been a one off and isolated temperature hike in and around the super El Nino of 1998 and unless that El Nino was in some way caused by the levels of CO2 in the atmosphere (and as far as I know no one suggests that it was), the satellite data suggests that we cannot detect any CO2 driven temperature change.
Of course, this may in part be explained by the sensitivity and accuracy of our temperature measurements. Say, if we can measure global temperatures to tenths of a degree, then observational data would permit climate sensitivity to be as high as about 0.25degC (ie., we have seen a rise in CO2 of about 120ppm from about 280 to about 400ppm and during this rise, we are unable to detect the signal of CO2 driven temperature changes). If we can measure global temperatures to one fifth of a degree, then climate sensitivity could be as high as 0.5degC, if we can measure global temperatures to a third of a degree, there is the possibility that climate sensitivity could be as high as about 0.75degC etc etc.
Thus one problem is the accuracy of our measurements. Can we really measure global temperatures to say a third of a degree, or is it in practice that our measurement efforts are such that we can only measure global temperatures to an accuracy of between half to one degree? It is because there is potential for such errors in our current assessment of global temperatures these past 150 years or so, that there is scope for argument that CO2 may do something. One cannot say that (at current levels of CO2) it actually does drive temperature, because no signal can be discerned over the noise, but because of the wide error margins in the accuracy of our temperature measurements, we cannot say from observational data, that it does not have any significant effect. It could be the case that due to the logarithmic effect of CO2, its effect was exhausted long before the pre-industrial level (claimed to be about 280ppm) was reached.
The take home is that climate sensitivity is so low that the effect (ie., the signal) cannot be measured within the limitations and parameters of our currently best available measurement equipment.
I would like to point out that heat emissions from our energy use are seldom if ever mentioned as a contributor to global warming, The fact is that heat emissions alone provide four times the energy that is required to raise the atmospheric temperature by the measured amount. This cannot simply be ignored. over the past century energy use has increased tenfold,and is currently over 16 terawatts, while CO2 concentration has increased by 25%. Present heat emissions are about 0.03w/m2. This has been ridiculed as being insignificant as compared to a present carbon forcing of 2,9w/m2, however we must look at the change over the past century of each of the contributing factors, i.e. what was the CO2 forcing a century ago as compared to the present. Probably no one knows.. I am not saying that the increase in CO2 contributes nothing, but the only thing we have a reasonable measure on, is the increase in heat emissions during the past century and it is enough to account for most of the effects we are experiencing. CO2 may cause a minor increase in heat retained, but increased conversion of CO2 by photosynthesis provides cooling by absorbing 5000 btus of solar energy or every pound of CO2 converted to trees, etc. The cooling effect may outweigh the minor heating effect (pure speculation).
In my opinion, to test these papers and their various assessments, the temperature record should be divided into slots (ie., the late 19th century/early 20th century cooling, the ~30 year warming to 1940, the ~30 year cooling between 1940 to 1970, the ~25 year warming to 1998, the 17 year stasis to date), and the authors should be required to list what positive and what negative forcings were used during each of these periods and why those forcings were used (ie, what evidential basis supports the forcings used).
One would then look at whether the climate sensitivity figure (as assessed by them) properly explains each of the distinct slots. One can also assess the reasonableness of the claimed forcings claimed to be operative during the period in question. If each slot cannot be explained by the climate sensitivity figure assessed by the author, there is a problem.
As many of us have been saying for years, the longer the current stasis continues, the lower the figure for climate sensitivity will become, and the longer it continues the more papers we will be seeing with climate sensitivity assessed at the low end of the IPCC range, or even below the low end.
The reasonableness of the 5th Assessment will not be judged on the date of its publication, but rather at the date when the next large international gathering takes place, or may be even 2020, since I seem to recall that, at Rio, China indicated that it would do nothing before 2020. This is a problem for the IPCC (and politicians on the bandwagon) since it is likely that their report will, at the material time, be seen to be irrelevant, having been superseded by a substantial number of papers assessing modest levels of climate sensitivity, and with modest climate sensitivity, the case for mitigation becomes increasingly weak, and the case for adaption becomes more attractive.
Richard Verney: Although it may be determined that climate sensitivity to CO2 is too low to be a consideration, the increase in CO2 is an indication that more heat is being emitted into the environment. Heat emissions from our energy consumption are four times the amount accounted for by the measured rise in atmospheric temperature. This heat goes somewhere besides the atmosphere. Some heats the land and water, melts glaciers etc., and some is lost by radiation and convection to space. Even if CO2 is found to be low sensitivity the damage from conventional energy will continue. Nuclear energy emits more than twice the total heat as its electrical output. CCS, carbon capture and storage, a program of international scope, is a preposterous boondoggle that should be exposed. To reduce CO2 by 1ppm requires the removal of 9,000,000 tons. The lower the sensitivity the less the benefit. I appreciate the opportunity to comment in agreement with your position.
Here are some basic numbers.
All Forcing 2013 (GHG and all others, IPCC AR5) –> +2.30 W/m2
Accumulating Energy 2013 (all known components) –> +0.58 W/m2
Negative Feedbacks 2013 (including increased OLR which is rarely mentioned) –> -1.72 W/m2 or -75%
Average Annual Temperature change for 0.58 W/m2 since 2004 when energy numbers are available –> 0.0C at surface, 0.002C deep ocean.
Temp C change per 1.0 W/m2 –> 0.0C/W/m2 to 0.003C/W/m2 –> same Zero as the paleoclimate.
Temp C change per 4.2 W/m2 doubling –> 0.0C to 0.012C
Last point should read.
Temp C change per 4.2 W/m2 doubling by 2080 –> 0.0C to 0.200C
philohaddad wrote “This heat goes somewhere besides the atmosphere. Some heats the land and water, melts glaciers etc., and some is lost by radiation and convection to space.”
Firstly, there is no significant convection into space because of the shortage of molecules to convey the kinetic energy. Radiating molecules like carbon dioxide and water receive energy conveyed by convection and radiate it away.
Secondly, the whole Earth plus atmosphere system acts like a black body and so it will radiate back to space close enough to the same incident insolation that it receives. Measurements near TOA rarely show a net difference of more than plus or minus half of one percent, and those measurements have uncertainties which effectively mean that there is no convincing evidence of any net imbalance at all. There probably is, though, when there is prolonged natural warming or cooling as part of the obvious 1,000 year and 60 year natural cycles. But temperature variations are the cause not the result.
This is another reason why there is no warming by carbon dioxide. The only transfers of thermal energy by radiation are from warmer to cooler regions, so radiation can transfer thermal energy only upwards in a troposphere, possibly following a random path between several molecules of those pollutants like water vapor and carbon dioxide until it breaks out of the maze and into space..
Brian says:
March 1, 2014 at 12:55 pm
“Do you mean that feedbacks add an additional 0.26 – 0.31 C to the 1.0 – 1.2 C, or are you claiming that feedbacks are negative, giving a total of 0.26 – 0.31 C? If the latter, you’ve run off the rails. ”
I mean the feedbacks are negative. If you see what I’ve done, I’m claiming that surface temperature changes over the last 17 years are zero. So I’m using Levitus 2010 to estimate that the only accumulation of heat in the system is 0.5W/m^2. We know that 0.52 doublings should force the system by 1.94W/m^2. But we only “see” 0.5W/m^2. So the feedback is -1.44W/m^2
“””””……Alex Hamilton says:
March 2, 2014 at 5:39 am
philohaddad wrote “This heat goes somewhere besides the atmosphere. Some heats the land and water, melts glaciers etc., and some is lost by radiation and convection to space.”
Firstly, there is no significant convection into space because of the shortage of molecules to convey the kinetic energy. Radiating molecules like carbon dioxide and water receive energy conveyed by convection and radiate it away…….”””””
Kevin Trenberth says that of the 390 W/m^2 radiated LWIR from the surface (at 288 K), only 40 W/m^2 escapes to space, presumably in the “atmospheric window” in the 10 micron region. The rest is absorbed by GHG and or clouds; H2O and CO2, being most prominent.
Now clouds, being water or ice, can absorb a wide range of LWIR spectrum energy (from the surface) at 10.1 micron spectrum center (288 K) and also LWIR emissions from atmospheric GHGs, which are emitted only at GHG molecular frequencies (non thermal spectrum). It is asserted, by experts who know more than I do, that atmospheric thermal energies are transferred by collisions to the GHG molecules, thereby raising the GHGs to some excited state, from which they subsequently re-radiate, isotropically at those specific spectral frequencies, characteristic of the particular GHG species. Thus cooling of the atmospheric gases at higher and higher altitudes, occurs only by eventual radiation by GHG gases at GHG specific resonance frequencies, primarily H2O and CO2 frequencies which are essentially Temperature independent, so there is no thermal radiation at frequencies characteristic of the atmosphere Temperature.
Now all of the LWIR radiations that get absorbed by CLOUDS, liquid, and solid water, are absorbed largely independent of the cloud Temperature, and help to determine the Temperature of the cloud, in concert with the altitude.
The cloud then, being solid or liquid, subsequently radiates a purely thermal LWIR radiation spectrum, that is entirely determined by the cloud Temperature, and is virtually always, a longer wavelength spectrum, than what was emitted from the surface, because of the lower (often much lower) cloud Temperature.
So the radiation to space from a cloudless sky, should consist ONLY of Temperature independent GHG band resonance radiation in addition to the 40 W/m^2, surface Temperature dependent radiation that Trenberth asserts escapes directly from the surface. Over dry cloudless deserts, that cooling radiation, would consist almost exclusively of CO2 band spectra, in addition to the surface Temperature thermal radiation.
So it seems to me, that over cloudless skies, the extra-terrestrial LWIR radiation should consist of only a Temperature independent H2O plus CO2 band spectrum, in addition to the surface Temperature dependent surface thermal emissions, that escape in the atmospheric window.
Over clouds, there would be an additional thermal spectrum component that is characteristic of the cloud Temperature, and each cloud layer, would have its own characteristic Temperature thermal spectrum.
Every extra-terrestrial LWIR spectrum, I have ever seen, consists of a surface Temperature dependent black body like thermal spectrum, with Temperature independent spectral holes at the prominent GHG resonant absorption band frequencies.
The atmosphere itself of course does not radiate thermal spectra at the atmosphere Temperature.
So why do people claim that the earth external emissions are at a 255 K or so characteristic Temperature, and the CO2 delaying raises the surface Temperature to 288 K.
With a 288 K surface Temperature, you can ONLY get a 255 K LWIR external spectrum, from high clouds at 255 K Temperature. At higher altitudes beyond all clouds, there cannot be Temperature dependent BB like radiation, at other than the surface Temperature of 288 K (on average of course).
Well unless you believe the atmospheric gases themselves can radiate a Temperature dependent thermal spectrum.
To Alex Hamilton: There should be no doubt that heat is transferred between earth and atmosphere by convection. When the cold winds come the earth is cooled. I will not conjecture how the heat leaves the atmosphere.
It would be nice, if somebody more knowledgeable would explain how at the higher beyond water altitudes, where atmospheric gas collision energies are much lower, they can still kick primarily CO2 molecules into the 15 micron resonance bending oscillations., since that must be the only remaining mode of radiative cooling.