Updated: Low Climate Sensitivity Estimated from the 11-Year Cycle in Total Solar Irradiance
By Dr. Roy W. Spencer
NOTE: This has been revised since finding an error in my analysis, so it replaces what was first published about an hour ago.
As part of an e-mail discussion on climate sensitivity I been having with a skeptic of my skepticism, he pointed me to a paper by Tung & Camp entitled Solar-Cycle Warming at the Earth’s Surface and an Observational Determination of Climate Sensitivity.
The authors try to determine just how much warming has occurred as a result of changing solar irradiance over the period 1959-2004. It appears that they use both the 11 year cycle, and a small increase in TSI over the period, as signals in their analysis. The paper purports to come up with a fairly high climate sensitivity that supports the IPCC’s estimated range, which then supports forecasts of substantial global warming from increasing greenhouse gas concentrations.
The authors start out in their first illustration with a straight comparison between yearly averages of TSI and global surface temperatures during 1959 through 2004. But rather than do a straightforward analysis of the average solar cycle to the average temperature cycle, the authors then go through a series of statistical acrobatics, focusing on those regions of the Earth which showed the greatest relationship between TSI variations and temperature.
I’m not sure, but I think this qualifies as cherry picking — only using those data that support your preconceived notion. They finally end up with a fairly high climate sensitivity, equivalent to about 3 deg. C of warming from a doubling of atmospheric CO2.
Tung and Camp claim their estimate is observationally based, free of any model assumptions. But this is wrong: they DO make assumptions based upon theory. For instance, it appears that they assume the temperature change is an equilibrium response to the forcing. Just because they used a calculator rather than a computer program to get their numbers does not mean their analysis is free of modeling assumptions.
But what bothers me the most is that there was a much simpler, and more defensible way to do the analysis than they presented.
A Simpler, More Physically-Based Analysis
The most obvious way I see to do such an analysis is to do a composite 11-year cycle in TSI (there were 4.5 solar cycles in their period of analysis, 1959 through 2004) and then compare it to a similarly composited 11-year cycle in surface temperatures. I took the TSI variations in their paper, and then used the HadCRUT3 global surface temperature anomalies. I detrended both time series first since it is the 11 year cycle which should be a robust solar signature…any long term temperature trends in the data could potentially be due to many things, and so it should not be included in such an analysis.
The following plot shows in the top panel my composited 11-year cycle in global average solar flux, after applying their correction for the surface area of the Earth (divide by 4), and correct for UV absorption by the stratosphere (multiply by 0.85). The bottom panel shows the corresponding 11-year cycle in global average surface temperatures. I have done a 3-year smoothing of the temperature data to help smooth out El Nino and La Nina related variations, which usually occur in adjacent years. I also took out the post-Pinatubo cooling years of 1992 and 1993, and interpolated back in values from the bounding years, 1991 and 1994.
Note there is a time lag of about 1 year between the solar forcing and the temperature response, as would be expected since it takes time for the upper ocean to warm.
It turns out this is a perfect opportunity to use the simple forcing-feedback model I have described before to see which value for the climate sensitivity provides the best fit to the observed temperature response to the 11-year cycle in solar forcing. The model can be expressed as:
Cp[dT/dt] = TSI – lambda*T,
Where Cp is the heat capacity of the climate system (dominated by the upper ocean), dT/dt is the change in temperature of the system with time, TSI represents the 11 year cycle in energy imbalance forcing of the system, and lambda*T is the net feedback upon temperature. It is the feedback parameter, lambda, that determines the climate sensitivity, so our goal is to find a value for a best value for lambda.
I ran the above model for a variety of ocean depths over which the heating/cooling is assumed to occur, and a variety of feedback parameters. The best fits between the observed and model-predicted temperature cycle (an example of which is shown in the lower panel of the above figure) occur for assumed ocean mixing depths around 25 meters, and a feedback parameter (lambda) of around 2.2 Watts per sq. meter per deg. C. Note the correlation of 0.97; the standard deviation of the difference between the modeled and observed temperature cycle is 0.012 deg. C
My best fit feedback (2.2 Watts per sq. meter per degree) produces a higher climate sensitivity (about 1.7 deg. C for a doubling of CO2) than what we have been finding from the satellite-derived feedback, which runs around 6 Watts per sq. meter per degree (corresponding to about 0.55 deg. C of warming).
Can High Climate Sensitivity Explain the Data, Too?
If I instead run the model with the lambda value Tung and Camp get (1.25), the modeled temperature exhibits too much time lag between the solar forcing and temperature response….about double that produced with a feedback of 2.2.
Discussion
The results of this experiment are pretty sensitive to errors in the observed temperatures, since we are talking about the response to a very small forcing — less than 0.2 Watts per sq. meter from solar max to solar min. This is an extremely small forcing to expect a robust global-average temperature response from.
If someone else has published an analysis similar to what I have just presented, please let me know…I find it hard to believe someone has not done this before. I would be nice if someone else went through the same exercise and got the same answers. Similarly, let me know if you think I have made an error.
I think the methodology I have presented is the most physically-based and easiest way to estimate climate sensitivity from the 11-year cycle in solar flux averaged over the Earth, and the resulting 11-year cycle in global surface temperatures. It conserves energy, and makes no assumptions about the temperature being in equilibrium with the forcing.
I have ignored the possibility of any Svensmark-type mechanism of cloud modulation by the solar cycle…this will have to remain a source of uncertainty for now.
The bottom line is that my analysis supports a best-estimate 2XCO2 climate sensitivity of 1.7 deg. C, which is little more than half of that obtained by Tung & Camp (3.0 deg. C), and approaches the lower limit of what the IPCC claims is likely (1.5 deg. C).
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
These discussions are aimed towards predicting future climate.Fortunately I was able to channel that great climate spirit Dr Norpag who provided me with the AR5 Summary for Policymakers 2012 which should save everyone a lot of time and trouble.
IPCC AR5 – Summary for Policymakers 2012
Our AR4 report included the following statement:
“The understanding of anthropogenic warming and cooling influences on climate has improved since the TAR, leading to very high confidence that the global average 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 ”
We further estimated an increase in temperature of about 3 degrees C. for a doubling of CO2.
We now realize that our knowledge of the factors controlling earth’s climate is much more limited than we previously thought and we are at this time unable to calculate the possible future effect of anthropogenic CO2 with any degree of certainty useful for policymakers. We apologise to those policymakers who embarked upon economically destructive carbon emission control schemes based upon our previous statements and similarly apologise to those members of the western intelligencia who spent sleepless nights worrying about the fate of the planet and their days trying to reduce their carbon footprint.
We can however make some possibly useful comments with suggestions for policymakers .
It is now clear that the patterns of the earths ocean current systems provide the best guide to the current state of the climate and the best clues as to developments over the next 20 – 30 years. Beyond that time span predictions are of little practical value.
Of particular note is the negative phase of the PDO which began about ten years ago and may well last for another 20 years. This suggests that La Ninas will be more frequent than El Ninos during this time span. A general earth cooling is thus more likely as was the case from 1940 to 1970 when similar conditions prevailed. Concurrent changes in the Arctic oscillation suggest a pattern of meridional atmospheric flow will be more common than the more latitudinal flows of warmer periods.
In addition the sun has entered a quiet phase with a dramatic drop in solar magnetic field strength since 2004. This reinforces the probability of a cooling phase on earth.
Policymakers may wish to note the following possible effects on earths climate for the next 20 – 30 years. A somewhat cooler world with lower SSTs usually means a dryer world. Thus droughts will be more likely in for example in California, and east Africa with possible monsoon failures in India. Northern Hemisphere growing seasons will be shorter with occasional early and late frosts and repeats of the harsh Central Asia (Mongolia) winters of 2009 – 10 . Cold European winters and cool cloudy summers will be more frequent .
There will be a steeper temperature gradient from the tropics to the poles so that tornadoes will be more violent and more frequent in the USA, At the same time the jet stream will swing more sharply North – South thus local weather world wide will be generally more variable with occasional more northerly heat waves and more southerly unusually cold snaps. In the USA hurricanes may strike the east coast with greater frequency.
The most general advice is that world food production may be subject to occasional serious severe restriction because of cold and drought. The use of food crops for biofuels should be abandoned and stockpiles built up for possible lean times ahead. There is no threat from the burning of fossil fuels for the forseeable future, indeed an increase in CO2 would positively help feed the burgeoning population.
For the next 20 years climate science should be devoted to improving and enlarging the entire climate data base in particular with regard to solar data of all kinds. No climate model runs should be made until 2025 by which time the inputs will be more relevant to the real world.
Leif says:
“The Sun’s magnetic field right now is what it was 108 years ago. So, based on your ‘logic’ the climate should be the same today as back then…”
Maybe! Or maybe in 108 more years from today assuming all remains the same. Unrealized climate change is an essential element of every extreme point of view, otherwise we could all relax and enjoy the weather. Or the lack of it considering recent history.
Tom in Florida: June 6, 2010 at 6:24 am
Someone, about a year ago or so, posted a chart on this blog showing the actually length of each solar cycle……..
You can use this until you come accros something better.
http://www.vukcevic.talktalk.net/SSCsl.htm
Cheers.
Another excellent post Dr. Spencer. I think your analysis is thorough enough, but there are still many unknowns here, and so too much left to speculation, especially in terms of how much the sun’s total irradiance truly does change during the shorter term versus the longer term trend. The Glory satellite to be launched later this year will help answer some of those questions, and I would send readers to this story:
http://www.physorg.com/news194025410.html
To get a good overview of the longer term issues really involved in solar irradiance. Also, this chart:
http://www.climate4you.com/Sun.htm#Global temperature and sunspot number
Shows the relationship between irradiance (which follows increasing sunspot numbers) and overall global temps over the past 50 years, and you can even see the ENSO signal on top of the cycle, especially in the strong El Nino years of 1998 and 1973.
Martin says:
“I not sure what comfort the skeptic can derive from Camp and Tung’s estimate of climate sensitivity, for one, it is an estimate of climate sensitivity to solar forcing, and there is no reason to assume that the climate sensitivity to CO2 forcing is the same, given how differently the forcings are coupled to the climate system.”
Correct me if I am wrong but isn’t SW radiation less likely to be perturbed by the climate system than LW radiation? If so, and there is a difference in sensitivity, would it not be more likely that solar forcing would be more likely to have high sensitivity?
Steve Fitzpatrick says:
“The best fit being for an effective (thermal) ocean depth of 25 meters, which is way too shallow, fairly well screams that the results are very doubtful.”
The primary thermocline is at 25 meters. Perhaps its a layering issue in a model that does not include a hard thermocline and as such the best fit is obtained there whereas with a properly designed ocean model better fits would be obtained at depths somewhat greater. So I am not sure how negatively this reflects on the result but maybe not much.
Dr Spencer> Even if the numbers you get are small, it seems that this analysis says something about the feedback. I understand that these feedbacks can’t be assumed to be instantaneous, but that there could be various positive and negative feedbacks acting in different characteristic time frames.
To make things simple, lets assume that the each solar cycle is exactly 11 year long, and that the method of summing cycles does indeed eliminate contributions from other forcings. Still, it seems to me that the total feedback at a certain time will depend not only of the solar forcing at that time (by instantaneous feedback), but also on the solar forcing at all other points in the 11 year cycle (by delayed feedback). So how do you isolate the feedback coming from the solar forcing acting at one particular time?
I believe that my question is closely related to Bart’s remark above that you are using a first order lag model.
Norman Page says:
June 6, 2010 at 8:40 am
Very good!
Climate sensitivity to doubling of CO2 is big on the agenda of true believers in AWG. But it is a dead issue because the work of Ferenc Mikolczi has shown that it may not even exist. He worked for NASA but his work first appeared in an obscure Hungarian journal in 2007. When his supervisors realized what he had done he was told not to talk about it, so he quit. His latest work is in E&E, Volume 21, No. 4 (2010). He shows that IPCC method of determining the water vapor feedback mechanism is error-prone and uses empirical data from sixty one years of radiosonde measurements to prove that feedback of water vapor effect on greenhouse-gas optical thickness is strongly negative, thoroughly contradicting the IPCC doctrine of it being positive. What this means is that computer models used by IPCC in predicting warming are all in error. In fact, if his theory stands there is no AGW now and there never was any. Warming, yes, but only of the natural kind.
dave springer the rcmp boat the roche did the passage both ways in the 1940s.it now sits in the vancouver maritime museum.i can see it from my house.
Bill Hunter says: “The primary thermocline is at 25 meters. ”
I don’t think this is correct. The well mixed layer of course varies a lot by latitude and with season (especially outside the tropics), ranging from a couple hundred meters to zero, but the area-weighted global average figure is usually taken as 50 meters or an little more. In the tropics (which receive the majority of solar energy, and where most ocean heat is accumulated) the average mixed layer is considerably deeper… near 100 meters or a bit more looks reasonable (based on a random grab of a few dozen ARGO profiles in the tropics).
If you have some reference showing and average of 25 meters to the thermocline, I would like to read that.
Arno Arrak says:
June 6, 2010 at 9:53 am
Climate sensitivity to doubling of CO2 is big on the agenda of true believers in AWG. But it is a dead issue because the work of Ferenc Mikolczi has shown that it may not even exist. He worked for NASA but his work first appeared in an obscure Hungarian journal in 2007. When his supervisors realized what he had done he was told not to talk about it, so he quit.
Actually, it was worse than that:
http://tallbloke.wordpress.com/2010/01/04/why-the-sun-is-so-important-to-climate/
It would be possible to measure the short-term climate sensitivity if we could actually tease a solar cycle signal out of the temperature series.
Every now and again, it seems as though there is a small one but then it is not consistent, produces opposite signals and so on.
If someone can show a solar cycle signal in the high resolution temperature data (as opposed to the annual data which is data selection in my opinion), then we can start measuring the sensitivity per Watt/m2.
Failing that, the answer must be that the sensitivity is low since a high number would be easier to find.
Steve Fitzpatrick says:
June 6, 2010 at 10:39 am
As I said earlier, thermoclines and haloclines are elastic and vary like a sheet waving in the wind, and react to tides and upwellings, volcanic or otherwise (earthquakes, volcanoes, etc.). They are not total barriers to heat transfer, and it is amusing to see modelers treat them as if it were ocean floor at 25 or 50 meters. As a deep sea fisherman at times, I have seen thermoclines disappear and move up and down, for unknown reasons, using sonar imaging, in large fresh and salt water bodies.
I don’t know this ipso facto– but I’ll bet that the thermocline is disrupted when El Nino is forming east of Japan and rumbling eastward. Heat, building up over the thermocline, had to be relieved by the event because it could not go lower fast enough, and it must have created havoc to deeper ocean while doing so, as well.
Other ocean oscillations possibly have their own similar mechanisms going on.
Who knows what the halocline does? It comes and goes in strength at high latitudes, mostly affecting the northern hemisphere.
in reality we are estimating based on 5 data points – thats how many solar cycles we are using. Call it what you will but there is still significant uncertainty given the small solar variation.
bubbagyro says:
June 6, 2010 at 11:56 am
I have seen thermoclines disappear and move up and down, for unknown reasons, using sonar imaging, in large fresh and salt water bodies.
Interesting. It’s a poorly understood subject. I wonder what happens when you pass electric current through temperature stratified water of varying salinity.
Steve F. says:
“If you have some reference showing and average of 25 meters to the thermocline, I would like to read that.”
More than likely what we have here is a difference in terminology. As a diver the thermocline is where the ocean makes a large step change in temperature. Thermocline in other vernaculars seems to mean the mixing zone. I am referring to the former.
Over half of the energy absorbed the oceans is absorbed by the upper 10 meters. By the time you get to 25 meters energy absorption is very low. The mixing layer above the thermocline mostly varies by wind activity. Since wave action only mixes energetically below the water abit less than twice the distance they stand above the water, mixing below that is a far slower process. The Rayleigh distribution on wave heights suggest only 1 in 1000 waves exceeds 18.6 meters and 1 in 100 above 15.1 meters and only 1 in 10 greater than 10.7 meters (wikipedia-Significant Wave Heights). Divers know almost where ever they dive the thermocline is going to be usually 25 meters or less and the step down in temperature which can occur in just a few inches is up to around 10 degrees. You can sit there and, I have on many occasions, wave your hand through it and feel a huge drop in water temperature.
So I what I am suggesting is perhaps the near immediate effect of sunlight penetrating is fairly well mixed in the upper 25 meters by energetic wave action at light energy penetration but there is a big temperature step that can be a shallower but seldom is a lot deeper than 50 meters that could potentially have an effect on models that assume more uniform ocean mixing to the depths you are likely calling the thermocline.
Gail Combs says:
June 6, 2010 at 7:54 am
Doug I do not think he was referring to the colors. I put the graphics up on two different screens and the areas do not match. Look at the area off the tip of south America or the area up near Alaska.
I did note the differences (using the same method). Note that the Unisys map shows Arctic and Antarctic waters while NOAA limits their coverage to areas presumably not covered by ice. They are also different days. NOAA is from June 3, while Unisys is from June 5.
Other differences could arise from using different contouring software.
I don’t the differences are big enough to indicate they are not using the same basic data set.
Bill Illis says:
June 6, 2010 at 10:57 am
This was my best attempt at teasing a temp trend out of solar data:
http://www.robertb.darkhorizons.org/SC24/Gr-DebINV2.PNG
What I really needed were the data points from the US Historical Temp data set, and to update the recent Debrecen data into the umbra/penumbra ratio. Also, the Greenwich data after 1974 (USAF/SOON?) is highly approximated and very wrongly assumed to be a formula. Debrecen will eventually fill in 1980-1985 to bridge the gap.
If you think about it, Umbra/Penumbra ratio is somewhat similar to L&P. The other part of Solar Phenomena not taken since 1974 are visible White Light Facula. Greenwich calculated TSI as a function of sunspots vs visible faculae for 100 years.
Note there is a time lag of about 1 year between the solar forcing and the temperature response, as would be expected since it takes time for the upper ocean to warm.
Can someone explain a bit more about the above statement? I can accept that a large cold reservoir will take time to warm up to a certain equilibrium temperature – maybe even a year – but the *response* should be immediate (or quite short, assuming the noise floor obscures the nascent signal). In other words, if I turn the sun off NOW, I’d expect everything to start cooling NOW (speed of light issues aside). I just can’t quite visualise the ocean taking a year to notice the giant lightbulb in the sky had gone out.
The only exception I can see for that is if there is an “intermediate reservoir” of heat, that is warmer than the “cold reservoir”, in which case the cold reservoir would warm to meet the intermediate reservoir, then they’d both cool together.
Where/what is that intermediate reservoir?
tallbloke says:
June 6, 2010 at 12:38 pm
Interesting. It’s a poorly understood subject. I wonder what happens when you pass electric current through temperature stratified water of varying salinity.
That’s also moving.
In a magnetic field.
Are you going to get more motion? Less motion? A different motion? A bigger electric field? A larger magnetic field? Heat? A research grant?
More questions than answers there I’m afraid…
Slightly off topic:
http://science.nasa.gov/science-news/science-at-nasa/2010/04jun_swef/
“The sun is waking up from a deep slumber, and in the next few years we expect to see much higher levels of solar activity. At the same time, our technological society has developed an unprecedented sensitivity to solar storms. The intersection of these two issues is what we’re getting together to discuss.”
—
Hope they aren’t too disappointed when this doom doesn’t really appear. All of my indicators point to a maximum of 20 +/-5 spots per year. Nothing to write home about. Cycle 25 should be somewhat weaker. Many are saying “But, but, but.. it has always done that every 11 years.” Yes, for the last ~310 years but the exit of cycle 23 showed signals of being very different even three years ago. I am not claiming I know the reason why this is occurring, that I do not know, but what comes will be interesting. My only guess is we are beginning to see the flop side of a multi-century cycle of some sort.
Maybe the sun does this. Fires up for ~300 years then subsides, fires up for ~300 years then subsides, … much like the 11 year cycle only centurial in nature. Just read an article from NASA saying they now see a ~0.05% decadal secular increase in the TSI across all satellites since the 70’s. Over 310 years, if present, would amount to ~1.5% increase. Lets see, 1.5% of 288 K is 4.3 K and seems a bit high to me. Could this be the same signature of the Maunder back in the early 1600’s before we had records? I guess anything is possible without data from that period and only time will tell.
Billy Liar says:
June 6, 2010 at 9:21 am
Norman Page says:
June 6, 2010 at 8:40 am
Very good!
Very very good indeed
[Charles Higley says:
June 5, 2010 at 9:03 pm
I greatly appreciate the discussion on climate sensitivity, but it should be included every now and then, for the reading public, that the doubling of atmospheric CO2 regularly mentioned in climate sensitivity does not mean that it will be doubling in the future. ]
I disagree with your assertion about the doubling. With business as usual burning of fossil fuels a doubling of co2 from 280 ppm starting point, 560 ppm will be reached quite easily later this century.
[With the 50 to 1 partitioning between sea and air, we would be hard put to raise CO2 by 20% if we tried by burning all our available carbon.]
Where did this 50 to 1 come from? When the economy is in full swing, we increase co2 into the atmosphere about 2% per year. Starting at 390 ppm to 560 ppm, we could reach 560 in 85 years. That is just straight emissions coming from the humans. Take into account as the earth warms, the oceans will absorb less and less co2, putting a larger portion into the atmosphere in the future.
[With the recent realization that the alarmists really do not know how much we emit and appear to use speculation and opinion, it is not reasonable to assume that we are having a great effect on atmospheric CO2.]
Possibly you only talk to the ignorant alarmists. As an alarmist, I would like to show that there is very easy accessible knowledge on the amount of co2 emitted into the air
http://en.wikipedia.org/wiki/List_of_countries_by_carbon_dioxide_emissions
As of 2006 in wikipedia it was about 28 gigatons. We are still in that range.
The main stream science behind climate sensitivity puts it about 3 degrees centigrade for a doubling of co2. Spencer comes out a lower number but still shows a change to a higher temperature. In Spencer’s own words, humans are changing the temperature on earth. No if ands or buts about it.
[Norman Page says:
June 5, 2010 at 9:37 pm
Added note .The same figure also shows that the uncertainties in the Albedo effect completely overwhelm the effect of the small change in TSI during the solar cycle which is the commonly used by the AGW crowd to minimise the solar influence and enhance the GHG effect by comparison.]
Data sets are showing in temperature change that the north polar reigion is increasing in temperature faster than the rest of the earth. About 2 to 3 times more. The melting of the artic ice which is one the most visible sensitive changes to observe, is loosing multi year ice every year. Part of the climate sensitivty measurement is a projected loss of ice and a warmig of the artic north waters. This is big. From there we get an ever northward moving of the thawing tundra. Which is another feedback that is postive for increasing the temperature of the earth.