Guest Post by Willis Eschenbach
ABSTRACT
The IPCC says that the expected change in temperature arising from a change in forcing is equal to the change in forcing times the climate sensitivity. The IPCC provides values we can use to estimate the total human and natural forcing change since 1850. The IPCC also proves estimates for the climate sensitivity. These can be multiplied to provide the IPCC expected temperature change since 1850. The value derived (best estimate per IPCC numbers = 1.4 °C warming since 1850) is twice the observed warming (HadCRUT best estimate = 0.7°C warming since 1850).
Recently I became puzzled by what seems to be a glaring discrepancy in the official IPCC numbers. The IPCC estimate of climate sensitivity is +3 [+2 to +4.5] °C per doubling.
We also have the IPCC estimate of the change in forcing since 1750, in Watts per square metre (W m-2). The human contribution to that forcing is given by the 2007 IPCC Summary for policymakers as:
The understanding of anthropogenic warming and cooling influences on climate has improved since the Third Assessment Report (TAR), leading to very high confidence that the globally averaged net effect of human activities since 1750 has been one of warming, with a radiative forcing of +1.6 [+0.6 to +2.4] W m-2.
This represents the best estimate plus [lower and upper bounds].
Now, a doubling of CO2 is estimated by the IPCC to produce a change in forcing of 3.7 W m-2. So if we divide the climate sensitivity (in degrees per doubling) by 3.7, we will get the climate sensitivity expressed in units of degrees per W m-2. This gives us the result:
Climate Sensitivity = +0.8 [+0.5 to +1.2] degrees per W m-2.
Finally, we know that sensitivity times the change in forcing gives us the temperature change. Using the IPCC estimates of both, this gives us:
+0.8 [+0.5 to +1.2] degrees per W m-2 times +1.6 [+0.6 to +2.4] W m-2
= +1.3 [+0.4 to +2.2] degrees of warming from human activities since 1750. (Errors throughout have been assumed to add in quadrature.)
Now, we don’t have very good temperature data before 1850, so we need to adjust for that. However, there was very little human effect on the climate from 1750 to 1850. CO2 levels were only slightly lower in 1750 than in 1850, the industrial revolution was in its infancy, little fossil fuels were burnt, sulfur emissions were negligible, no fluorocarbons were emitted. Since the 1750-1850 anthropogenic contribution is very small compared to the total anthropogenic forcing, that IPCC based calculation of temperature change from humans of +1.3 [+0.4 to +2.2] degrees can be taken as the best estimate and bounds of the human caused temperature change since 1850.
For our final estimate, in addition to the human forcings since 1850 we need to add the natural forcings. The IPCC includes only one of these, solar forcing. The IPCC estimates that changes in solar forcing in the ~250 years since 1750 was 0.12 W m-2. For our rough calculations, we can make a crude but adequate estimate that three fifths of this change occurred since 1850. Adding solar forcing to the earlier equations makes the IPCC calculated temperature change from human and natural forcings combined since 1850 slightly greater, at +1.4 [+0.4 to +2.3] degrees.
Now, here’s the problem with that, and it’s a very big problem. According to the HadCRUT dataset (monthly dataset here, with notes here), the total temperature change 1850 – 2006 is +0.7 [+0.5 to +0.9] degrees. In other words, the world has warmed by around three-quarters of a degree (best estimate 0.7°C) since 1850. That’s nowhere near 2.3°C, the high end of what the IPCC says should have happened since 1850. It’s only half of the IPCC’s most likely number. It is just above the IPCC’s lower bound. So the IPCC method, using the IPCC numbers, way overestimates the historical temperature rise.
What can we conclude from this mismatch between observations and calculations? There are a number of possible explanations, in no particular order.
1. The sensitivity numbers are too high, and the forcing numbers are correct. If that is the case, the sensitivity is +1.5 [+0.5 to +2.4] degrees per doubling of CO2, a much lower and narrower range than the +3 [+2 to +4.5] range espoused by the IPCC.
2. The forcing numbers are too high, and the sensitivity numbers are correct. That gives us a calculated change in forcing since 1850 of +0.9 [+0.5 to +1.4] W/m2. Again this is much lower and more narrowly bounded than the canonical IPCC range of +1.7 [+0.7 to +2.5] W/m2 including solar. Note that in both this and the previous case, the relatively narrow bounds of the temperature observations have constrained narrow bounds on the underlying forcings or sensitivities.
3. Both the sensitivity and the forcing numbers are too high. This would limit possibilities to values such that the product of the two give us +0.7 [+0.5 to +0.9] degrees of warming. If the reductions were proportional, the forcing and the sensitivity would each need to be cut to about 70% of the IPCC numbers.
4. There are other mechanisms at play (e.g. cosmic rays, plankton aerosol production, thunderstorms) that the IPCC is not accounting for.
5. I’ve made a foolish mathematical mistake.
6. Climate may not obey a linear relationship between forcing and temperature change. My calculations are based on the IPCC assumption that a change in temperature can be calculated as a constant called “climate sensitivity” times the change in forcing. However, climate sensitivity may not be (and in my view is not) a constant. Instead, in my view climate sensitivity is a function of T, which changes the equation.
7. This is the “missing heat” that Trenberth referred to.
8. Something completely different that I haven’t thought of.
I couldn’t even begin to say which of those, or how many of those, if any of those, are actually going on …
Anyhow, that’s the oddity. If we multiply the IPCC historical forcing change since 1850 times the IPCC climate sensitivity to get the IPCC estimated temperature change since 1850, the result is nothing like the historical temperature change. The high IPCC estimate (2.3°C) is three times the actual change (0.7°C) since 1850. Clearly, something is wrong. Depending on which explanation we choose, we have different conclusions, none of which seems compelling.
Assistance and ideas welcome …
Over at climate4you.com there is clear evidence that most of the recent warming was caused by a 5% decrease in cloud cover, which caused about 0.35 deg C warming out of the observed 0.4deg warming during the satellite period.
Therefor CO2 caused only 0.05 c warming compared to the estimate of 0.4-0.6
Ie the sensitivity is 10 times to high.
The ERBE results back up the cloud results, shortwave absorption is up, and the planet responds by losing more energy (longwave increased) demonstrating negative feedback.
Willis says “Where did I say that my numbers did not include aerosols and the rest? Take a look at the SPM? The IPCC forcing figures are from all sources of forcing, not just CO2 …”
My interpretation of the 3 degrees per doubling does not include aerosols, and it can’t because you can’t predict how those will change with CO2. The aerosols are an additional negative effect that prevailed during the 40’s to 70’s as the aerosol haze/cloud area expanded to its current size. Note that the aerosol effect is limited from growing further by its short residence time in the atmosphere, so its growth does not figure into future projections, and should not unless places like Africa industrialize rapidly.
Willis – the observed 0.74 C temperature increase is consistent with the IPCC estimate of 1.6 W/m^2 “forcing”, but the confusion arises because of their unusual definition of forcing; I would have preferred a different term, such as “delta forcing”. The 1.6 figure does not refer to a TOA energy imbalance (ignoring feedbacks) but rather to an estimated change in the variables responsible for creating an imbalance since 1750. As noted, these include CO2, aerosols, and solar changes.
If the atmosphere had instantaneously become imbalanced by 1.6 W/m^2 in 1750, and no perturbations had been added since then, but feedbacks had been allowed to proceed, we would now be close to equilibrium, and the equilibrium climate sensitivity estimate of about 1.4 C should be close to realization. In fact, however, much of the imbalancing factors (particularly CO2 increases) have changed mainly in the past half century, and due to the thermal inertia of the climate system (particularly the deep ocean), we are only part way there. In the process, the imbalance has been reduced by the rise in temperature, so that the current estimate of forcing in its more traditional sense has diminished to a currently estimated 0.9 W/m^2. If this were alllowed to come to equilibrium without further perturbations, the 1.4 C figure you cite would be more or less what we should expect on the basis of current climate sensitivity estimates.
RobJM, a decrease in cloud cover in a time of warming (if true) would just kill the ideas of Spencer and Lindzen who say the opposite should happen to provide a negative feedback. For AGW it would provide an additional positive feedback that they don’t really consider yet.
Dave Springer says:
“Most of the world and evidently half the U.S. electorate as well believes the United States is too powerful, too wealthy, too arrogant, and too willing to flex its muscle around the world and they desperately want that to change in a big way. Hobbling the U.S. economy by making it pay dearly for every ton of CO2 emitted while giving “developing” countries a free pass to keep on growing their emissions of CO2, methane, and black carbon without restriction will accomplish their goal.”
Dave,
The objective of the Copenhagen conference and the up coming Mexican conference is in addition to giving a free pass to the developing countries to pollute is to send billions of tax dollars to corrupt, comically inept, third world governments. The estimate for the current waste for aid dollars is 1 to 10. 10% of each dollar is effectively spent. The remainder goes to middle men, government officials, other non-related projects, and “consultants”.
The Green Parties are the fantasy parties. Money grows on trees. When I traveled through Europe this summer I saw field after field filled with wind turbines, none of which were turning as there was no wind. Practical engineering issues such as what to do with the wind power that is generated when there is no load or load requirements when there is no wind are ignored.
CO2 is beneficial to the biosphere. Plants eat CO2. The planet’s response to a change in forcing is obviously negative not positive. Global warming is beneficial to the biosphere. (70% of the planet is covered by water. Warmer planet more precipitation.)
The biosphere expands into the higher latitude regions when the planet warms (i.e. Most of the warming occurs for high latitude regions. Storms severity is less not more for a warmer planet. Less difference in temperature from high latitude to low latitude regions.)
In my earlier comment, I forgot to mention an important factor that will significantly influence future temperature increases. The 1.6 W/m^2 IPCC estimate balances GHG forcings with the negative forcings due to aerosols. However, aerosol forcing is not increasing, and with pollution remediation measures, may actually be diminishing in much of the world. Therefore, as CO2 concentrations rise, the ratio between CO2 and aerosols will also rise. As a result, one can’t extrapolate to the future from current CO2/aerosol balances, but must include the increasing level of “unmasking” of CO2 effects as a result of the changing ratio.
Willis Eschenbach: You’ve been sifting through the IPCC positions for a while. Can you recommend a decent layman’s overview of it all?
I’m looking for something reasonably honest and impartial.
Roger Knights says: October 23, 2010 at 4:40 am
(John Kehr also take note) Yes I think so. It was what really clinched AGW as conscious BS for me, when Schmidt claimed to refute Monkton and Monbiot piously quoted Schmidt, but Monckton really wiped the carpet with Schmidt and Monbiot, to which Schmidt replied with a deafeningly loud silence – but still continued carping over Monckton’s original article.
@ur momisugly Peter D. Tillman
No extra-heat in the pipeline …
http://www.pas.rochester.edu/%7Edouglass/papers/KD_InPress_final.pdf
Jim D says:
October 23, 2010 at 11:02 am
Jim, I’m just using the IPCC figures for those things, from the FAR Summary for Policymakers.
Willis, option 8 does provide a solution to this conundrum.
The actual increase in temperature is 1.4C, but its the data that’s wrong. Our modern temperature records are accurate, but the older ones overestimated the temperature. This can be corrected by lowering the earlier records to bring them into line. Some of this correction has already been done to achieve the apparent 0.7C increase, and I’m sure that NASA and HADCrut will be able to find more records that can be adjusted to suit.
Fred Moolten (echoing prior claims) says “…and due to the thermal inertia of the climate system (particularly the deep ocean), we are only part way there”
Fred, or anybody else, please post some numbers. How much heat is being stored in the ocean, i.e. tell us what the mass is and what the rate of warming is. Please show how you arrived at the rate of warming (real world measurements? Working backwards from missing heat?) Next, please show the rate at which the heat is sent to the deep ocean by showing what the water flow is from the warm surface to the depths and the consequent energy transfer. Then show how that arrives at the measured rate of deep ocean warming.
JJB MKI, I think your explanation is the best one so far.
Please go ask Lucia for her lumped parameter model which I named “lumpy”
You’ll see all the things you left out.
http://rankexploits.com/musings/2008/lumpy-vs-model-e/
Thanks again, Willis, for another interesting and useful post which gets to the core of how the IPCC cabal of climate scientists clearly haven’t a clue about what really drives Earth’s climate. They seem unable to back off from the ridiculous CAGW conjecture in the face of a mountain of contrary evidence – perhaps too much political pressure and vested interest.
My view is that your arithmetic is correct, and reason 6 gets close to explaining the issue:-
“6. Climate may not obey a linear relationship between forcing and temperature change. My calculations are based on the IPCC assumption that a change in temperature can be calculated as a constant called “climate sensitivity” times the change in forcing. However, climate sensitivity may not be (and in my view is not) a constant. Instead, in my view climate sensitivity is a function of T, which changes the equation.”
First, I think average global temperature is a very poor indicator of our planets energy flows. The amount of energy in the system varies every second of the day and is the driver of all the varying phenomenon we call weather. We do not have the capability to measure the ever changing Earth system energy level and I suspect the estimates we currently use are far off the mark.
The system acts like a complex driven oscillator and non-linear deterministic chaos determines the outcomes we observe at all time scales. Sometimes there is apparent order when linear behaviour occurs, but turbulence and non-linear behaviour can happen at any time, causing the apparent linearity to break down. Turbulence increases when extra energy is in the system, and this in turn increases our planets ability to cool because of maximum entropy production. The system tends to undershoot and overshoot when changing between laminar and turbulent flow.
Long-term weather/climate is made up of many overlapping short-medium-long term quasi-cycles, most of which follow a sinusoidal oscillating curve. This makes any detailed predictions about long-term weather regime/climate impossible to achieve. However, a broad based forecast is possible as shown below:-
1410-1500 cold – Low Solar Activity(LSA?)-(Sporer minimum)
1510-1600 warm – High Solar Activity(HSA?)
1610-1700 cold – (LSA) (Maunder minimum)
1710-1800 warm – (HSA)
1810-1900 cold – (LSA) (Dalton minimum)
1910-2000 warm – (HSA)
2010-2100 (cold???) – (LSA???)
Eric – One good source is the paper by Levitus et al at Ocean Heat Content
The combined effects of aerosols and ocean heat storage can account for the current temperature increases based on the range of climate sensitivities that are typically estimated.
Nullius in Verba says: “…The problem with high sensitivities is that we’ve already seen half a doubling (logarithmically speaking), so we ought to be seeing half the predicted warming. Clearly we’re not. So to explain that, they have invented lags and time delays that shift the consequences decades into the future…”
I’ve suspected for a long time that they’re making this stuff up as they go.
Willis, OK, looking at the SPM, remarkably the total anthropogenic forcing is very much like the CO2-alone forcing, but with a wider error bar due to the wide error bars for aerosol effects. It appears the true aerosol effect must have been in the upper part of its error bar range, but you see the error bars surround the observed trend, so is there really a problem?
Steven Mosher says:
October 23, 2010 at 1:01 pm
Thanks, Steven. Actually I followed the development of “Lumpy” during the time that Lucia was developing it. Very interesting. Still not sure what I left out, or exactly how Lumpy would explain where the missing half a W/m2 went. If you know, let me know.
The feedback has to be negative or temperatures would have shot off to the limit millions of years ago.
My guess is a feedback of -2/3. An initial rise in temp of 1.2 for doubling CO2 would cause negative feedback of 2/3 of that, leaving 1/3 of 1.2 = 0.4.
That’s insignificant, so the warming we’ve seen would be due to normal natural changes. I think it was mostly an increase in the solar wind due to a more active sun causing more cosmic rays to reach the earth, causing changes in cloud cover.
A less active Sun, as it is now, should resolve that over the next decade.
By the way, I cancelled my subscription to Scientific American a year ago. They sent me a letter inviting me to re-subscribe. I sent it back saying they could mail me when they decided to live up to the Scientific part of their name. One small half-hearted article isn’t enough.
The really fundamental puzzle which I have is this: as far as I can ascertain, NONE of the ‘warmists’ and the world’s Lemming-like politicians seem to have read Kyoto.
The Kyoto protocol talks about reducing CO2 EQUIVALENT – not CO2 itself..! As we all know (or the contributors on this side of the fence at least know) that – for a start- water vapour is a far more potent greenhouse gas than CO2. However – many so-called ‘green’ projects talk about ‘only’ producing ‘harmless water vapour’..!
Oh, really..?
Its all down to the mantra that CO2 is nasty black stuff that chokes children and bunnies – not that it is an essential feedstock for plants, and that the atmospheric concentration of CO2 has been FAR higher in history than it is today.
I still can not recognize any anthropogenic forcing in the Greenland record. For most of the time it was warmer.
http://www.ncdc.noaa.gov/paleo/pubs/alley2000/alley2000.html
How bizarre it is after so many years that there is so much confusion about so few numbers at the base of so large an important issue.
The science is settled. There is consensus. 95% certainty.
Of course things don’t add up, make sense, bring us clarity of vision. The asylum is being run by the inmates.
I just got done doing a similar comparison. Chapter 8 in the AR4 quotes Dr. Hansen saying without feedbacks the sensitivity is 1.2°C but he adds the feedbacks from clouds and it increases to 3.2° ± 0.7°C. Here’s a graphic I put together showing that the 280 – 380 ppm increase last century falls in line with the 1.2° value but the 3.2° ± 0.7° overshoots the mark by a wide margin.
http://i55.tinypic.com/25738cm.jpg
stacase@hotmail.com
On further reflection, I find it hard to believe that this hasn’t been done before.
Probably has.
Jim D says:
October 23, 2010 at 11:21 am
RobJM, a decrease in cloud cover in a time of warming (if true) would just kill the ideas of Spencer and Lindzen who say the opposite should happen to provide a negative feedback. For AGW it would provide an additional positive feedback that they don’t really consider yet.
Well, the “opposite” does happen daily in the Tropics as Willis so elegantly described a while back, of course coupled with the condensation of cloud water vapor into rain with the resultant loss of much heat to space every 24 hr. – a mechanism which also supplies a ready explanation for why water vapor has apparently never caused a runaway heating event all by itself, and why CO2 is not going to be able to cause water vapor to do anything more than it has always done.