Guest Post by Willis Eschenbach
In the leaked version of the upcoming United Nations Intergovernmental Panel on Climate Change (UN IPCC) Fifth Assessment Report (AR5) Chapter 1, we find the following claims regarding volcanoes.
The forcing from stratospheric volcanic aerosols can have a large impact on the climate for some years after volcanic eruptions. Several small eruptions have caused an RF for the years 2008−2011 of −0.10 [–0.13 to –0.07] W m–2, approximately double the 1999−2002 volcanic aerosol RF.
and
The observed reduction in warming trend over the period 1998–2012 as compared to the period 1951–2012, is due in roughly equal measure to a cooling contribution from internal variability and a reduced 2 trend in radiative forcing (medium confidence). The reduced trend in radiative forcing is primarily due 3 to volcanic eruptions and the downward phase of the current solar cycle.
Now, before I discuss these claims about volcanoes, let me remind folks that regarding the climate, I’m neither a skeptic nor am I a warmist.
I am a climate heretic. I say that the current climate paradigm, that forcing determines temperature, is incorrect. I hold that changes in forcing only marginally and briefly affect the temperature. Instead, I say that a host of emergent thermostatic phenomena act
quickly to cool the planet when it is too warm, and to warm it when it is too cool.
One of the corollaries of this position is that the effects of volcanic eruptions on global climate will be very, very small. Although I’ve demonstrated this before, Anthony recently pointed me to an updated volcanic forcing database, by Sato et al. Figure 1 shows the amount of forcing from the historical volcanoes.
Figure 1. Monthly changes in radiative forcing (downwelling radiation) resulting from historical volcanic eruptions. The two large recent spikes are from El Chichon (1983) and Pinatubo (1992) eruptions. You can see the average forcing of -0.1 W/m2 from 2008-2011 mentioned by the IPCC above. These are the equilibrium forcings Fe, and not the instantaneous forcing Fi.
Note that the forcings are negative, because the eruptions inject reflective aerosols into the stratosphere. These aerosols reflect the sunlight, and the forcing is reduced. So the question is … do these fairly large known volcanic forcings actually have any effect on the global surface air temperature, and if so how much?
To answer the question, we can use linear regression to calculate the actual effect of the changes in forcing on the temperature. Figure 2 shows the HadCRUT4 monthly global surface average air temperature.
Figure 2. Monthly surface air temperatures anomalies, from the HadCRUT4 dataset. The purple line shows a centered Gaussian average with a full width at half maximum (FWHM) of 8 years.
One problem with doing this particular linear regression is that the volcanic forcing is approximately trendless, while the temperature has risen overall. We are interested in the short-term (within four years or so) changes in temperature due to the volcanoes. So what we can do to get rid of the long-term trend is to only consider the temperature variations around the average for that historical time. To do that, we subtract the Gaussian average from the actual data, leaving what are called the “residuals”:
Figure 3. Residual anomalies, after subtracting out the centered 8-year FWHM gaussian average.
As you can see, these residuals still contain all of the short-term variations, including whatever the volcanoes might or might not have done to the temperature. And as you can also see, there is little sign of the claimed cooling from the eruptions. There is certainly no obvious sign of even the largest eruptions. To verify that, here is the same temperature data overlaid on the volcanic forcing. Note the different scales on the two sides.
Figure 4. Volcanic forcing (red), with the HadCRUT4 temperature residual overlaid.
While some volcanoes line up with temperature changes, some show increases after the eruptions. In addition, the largest eruptions don’t seem correlated with proportionately large drops in temperatures.
So now we can start looking at how much the volcanic forcing is actually affecting the temperature. The raw linear regression yields the following results.
R^2 = 0.01 (a measure from zero to one of how much effect the volcanoes have on temperature) "p" value of R^2 = 0.03 (a measure from zero to one how likely it is that the results occurred by chance) (adjusted for autocorrelation). Trend = 0.04°C per W/m2, OR 0.13°C per doubling of CO2 (how much the temperature varies with the volcanic forcing) "p" value of the TREND = 0.02 (a measure from zero to one how likely it is that the results occurred by chance) (adjusted for autocorrelation).
So … what does that mean? Well, it’s a most interesting and unusual result. It strongly confirms a very tiny effect. I don’t encounter that very often in climate science. It simultaneously says that yes, volcanoes do affect the temperature … and yet, the effect is vanishingly small—only about a tenth of a degree per doubling of CO2.
Can we improve on that result? Yes, although not a whole lot. As our estimate improves, we’d expect a better R^2 and a larger trend. To do this, we note that we wouldn’t expect to find an instantaneous effect from the eruptions. It takes time for the land and ocean to heat and cool. So we’d expect a lagged effect. To investigate that, we can calculate the R^2 for a variety of time lags. I usually include negative lags as well to make sure I’m looking at a real phenomenon. Here’s the result:
Figure 5. Analysis of the effects of lagging the results of the volcanic forcing.
That’s a lovely result, sharply peaked. It shows that as expected, after a volcano, it takes about seven-eight months for the maximum effects to be felt.
Including the lag, of course, gives us new results for the linear regress, viz:
R^2 = 0.03 [previously 0.01] "p" value of R^2 = 0.02 (adjusted for autocorrelation) [previously 0.03] Trend = 0.05°C per W/m2, OR 0.18 ± 0.02°C per doubling of CO2 [previously 0.13°C/doubling] "p" value of the Trend = 0.001 (adjusted for autocorrelation). [previously 0.02]
As expected, both the R^2 and the trend have increased. In addition the p-values have improved, particularly for the trend. At the end of the day, what we have is a calculated climate sensitivity (change in temperature with forcing) which is only about two-tenths of a degree per doubling of CO2.
Here are the conclusions that I can draw from this analysis.
1) The effect of volcanic eruptions is far smaller than generally assumed. Even the largest volcanoes make only a small difference in the temperature. This agrees with my eight previous analyses (see list in the Notes). For those who have questions about this current analysis, let me suggest that you read through all of my previous analyses, as this is far from my only evidence that volcanoes have very little effect on temperature.
2) As Figure 5 shows, the delay in the effects of the temperature is on the order of seven or eight months from the eruption. This is verified by a complete lagged analysis (see the Notes below). That analysis also gives the same value for the climate sensitivity, about two tenths of a degree per doubling.
3) However, this is not the whole story. The reason that the temperature change after an eruption is so small is that the effect is quickly neutralized by the homeostatic nature of the climate.
Finally, to return to the question of the IPCC Fifth Assessment Report, it says:
There is very high confidence that models reproduce the more rapid warming in the second half of the 20th century, and the cooling immediately following large volcanic eruptions.
Since there is almost no cooling that follows large volcanic eruptions … whatever the models are doing, they’re doing it wrong. You can clearly see the volcanic eruptions in the model results … but you can’t see them at all in the actual data.
The amazing thing to me is that this urban legend about volcanoes having some big effect on the global average temperature is so hard to kill. I’ve analyzed it from a host of directions, and I can’t find any substance there at all … but it is widely believed.
I ascribe this to an oddity of the climate control system … it’s invisible. For example, I’ve shown that the time of onset of tropical clouds has a huge effect on incoming solar radiation, with a change of about ten minutes in onset time being enough to counteract a doubling of CO2. But no one would ever notice such a small change.
So we can see the cooling effect of the volcanoes where it is occurring … but what we can’t see is the response of the rest of the climate system to that cooling. And so, the myth of the volcanic fingerprints stays alive, despite lots of evidence that while they have large local effects, their global effect is trivially small.
Best to all,
w.
PS—The IPCC claims that the explanation for the “pause” in warming is half due to “natural variations”, a quarter is solar, and a quarter is from volcanoes. Here’s the truly bizarre part. In the last couple decades, using round numbers, the IPCC predicted about 0.4°C of warming … which hasn’t happened. So if a quarter of that (0.1°C) is volcanoes, and the recent volcanic forcing is (by their own numbers) about 0.1 W/m2, they’re saying that the climate sensitivity is 3.7° per doubling of CO2.
Of course, if that were the case we’d have seen a drop of about 3°C from Pinatubo … and I fear that I don’t see that in the records.
They just throw out these claims … but they don’t run the numbers, and they don’t think them through to the end.
Notes and Data
For the value of the forcing, I have not used the instantaneous value of the volcanic forcing, which is called “Fi“. Instead, I’ve used the effective forcing “Fe“, which is the value of the forcing after the system has completely adjusted to the changes. As you might expect, Fi is larger than Fe. See the spreadsheet containing the data for the details.
As a result, what I have calculated here is NOT the transient climate response (TCR). It is the equilibrium climate sensitivity (ECS).
For confirmation, the same result is obtained by first using the instantaneous forcing Fi to calculate the TCR, and then using the TCR to calculate the ECS.
Further confirmation comes from doing a full interative lagged analysis (not shown), using the formula for a lagged linear relationship, viz:
T2 = T1 + lambda (F2 – F1) (1 – exp(-1/tau)) + exp(-1/tau) (T1 – T0)
where T is temperature, F is forcing, lambda is the proportionality coefficient, and tau is the time constant.
That analysis gives the same result for the trend, 0.18°C/doubling of CO2. The time constant tau was also quite similar, with the best fit at 6.4 months lag between forcing and response.
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In this case it’s the Sato paper, which provides a dataset of optical thicknesses “tau”, and says:
The relation between the optical thickness and the forcings are roughly (See “Efficacy …” below):
instantaneous forcing Fi (W/m2) = -27 τ
adjusted forcing Fa (W/m2) = -25 τ
SST-fixed forcing Fs (W/m2) = -26 τ
effective forcing Fe (W/m2) = -23 τ
And “Efficacy” refers to
Hansen, J., M. Sato, R. Ruedy, L. Nazarenko, A. Lacis, G.A. Schmidt, G. Russell, et al. 2005. Efficacy of climate forcings. J. Geophys. Res., 110, D18104, doi:10.1029/2005/JD005776.
Forcing Data
For details on the volcanic forcings used, see the Sato paper, which provides a dataset of optical thicknesses “tau”, and says:
The relation between the optical thickness and the forcings are roughly (See “Efficacy …” below):
instantaneous forcing Fi (W/m2) = -27 τ
adjusted forcing Fa (W/m2) = -25 τ
SST-fixed forcing Fs (W/m2) = -26 τ
effective forcing Fe (W/m2) = -23 τ
And “Efficacy” refers to
Hansen, J., M. Sato, R. Ruedy, L. Nazarenko, A. Lacis, G.A. Schmidt, G. Russell, et al. 2005. Efficacy of climate forcings. J. Geophys. Res., 110, D18104, doi:10.1029/2005/JD005776.
(Again, remember I’m using their methods, but I’m not claiming that their methods are correct.)
Future Analyses
My next scheme is that I want to gin up some kind of prototype governing system that mimics what it seems the climate system is doing. The issue is that to keep a lagged system on course, you need to have “overshoot”. This means that when the temperature goes below average, it then goes above average, and then finally returns to the prior value. Will I ever do the analysis? Depends on whether something shinier shows up before I get to it … I would love to have about a dozen bright enthusiastic graduate students to hand out this kind of analysis to.
I also want to repeat my analysis using “stacking” of the volcanoes, but using this new data, along with some mathematical method to choose the starting points for the stacking … which turns out to be a bit more difficult than I expected.
Previous posts on the effects of the volcano.
Prediction is hard, especially of the future.
Pinatubo and the Albedo Thermostat
Dronning Maud Meets the Little Ice Age
New Data, Old Claims about Volcanoes
Volcanoes: Active, Inactive and Interactive
Stacked Volcanoes Falsify Models
Beta Blocker says:
September 23, 2013 at 11:33 am
……. to demonstrate or to disprove Willis’ theory that the earth’s climate system operates mostly as a self-regulating, self-stabilizing heat engine?
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I’ve been thinking about that one…..long and hard….didn’t want to bring it up and derail this volcano thread
Maybe Willis will do another thread on it….
Latitude says:
September 23, 2013 at 12:29 pm
IMO that’s not a controversial assertion, if its brunt is to argue that earth is homeostatic most of the time, or all of the time, given long enough. Its temperature range for billions of years has been roughly from about 50 degrees below zero C during Snowball Earths to perhaps +40 degrees C during the melt-off phase of these global glacial interludes.
But for the past 550 million years, that range has narrowed to around +7 degrees C during Icehouse phases & +23 degrees C during Hothouses. As we’re in an interglacial cycle in a glacial epoch, we’re presently 14-15 degrees C, depending upon whose special pleading seems more convincing to you.
Depends on scale I would suggest. At fine scale micro climates, local address would come into play regarding self-adjusting thermostats. Which could be why we have fairly well-defined ranges in each of our climate zones, allowing thermostats free range inside those boundaries. On a larger longer scale (IE large areas of extreme heat, cold, etc over an extended period of time), something happens (IE rare oscillation convergence, equatorial event, etc) that fouls up the thermostats and we are impacted by powerful regional, hemispheric, and global forcings that overcome (for a while anyway) local thermostats resulting in extensive and longer term climate range excursions outside the norm. Again just pondering.
Wayne: 1.4 degC was the most likely climate sensitivity derived by Paul_K from monthly observed changes in: albedo due to aerosols (radiative forcing), LWR emitted through the TOA, and surface temperature. He performed a best fit of these observations to climate sensitivity, the depth of the mixed layer, and heat diffusion below the mixed layer. Values of ECS below 0.9 degC or above 1.7 degC couldn’t be made to match observations by any changes in the size of the mixed layer and diffusion of heat below it.
Interestingly, 1.4 degC is similar to Nic Lewis’s value of 1.6 degC (1.3-2.3), Otto, et al and other work based on recent observations. All of these number arise from calculations, but the require equations that properly describe all of the important heat flows. The observations also contain uncertainty. These numbers are results that depend on the quality of the analysis, not opinions.
milodonharlani says:
September 23, 2013 at 12:46 pm
I should specify global mean T, to the extent such a figure can be measured or reconstructed.
There appears to be a downside limit to runaway cooling & at least until the sun goes red giant, an upside as well. That may change as the sun becomes more radiant & as our planet loses surface water.
“I hold that changes in forcing only marginally and briefly affect the temperature. Instead, I say that a host of emergent thermostatic phenomena act quickly to cool the planet when it is too warm, and to warm it when it is too cool.”
A glance at any global temperature data, on any timescale, proves this idea wrong.
Iben Browning did a lot of work on this before he died. He showed something like a Kondratieff Wave for tidal pressure on the earth and volcanic activity. Increased volcanic activity in the northern hemisphere when coupled with increased solar activity warming the equatorial region might appear to offset but results in the jet stream whipping back and forth. Even if the overall global temperature doesn’t drop, crops don’t do well with the instability.
Pamela Gray says:
September 23, 2013 at 12:55 pm
Depends on scale I would suggest.
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Since we did it anyway……
That’s what I think too Pamela….looks like the planets default setting is colder…a lot colder
In my field we try to work with extremes…..because the extremes are very unstable…either the extreme of high or lowb
All I see is that we’re in an extreme and it’s unstable…
Not that the planet is regulating it back to some “normal”…..but the default setting is normal and there’s something else limiting that’s making it bounce around…sorta the opposite of the way Willis sees it
Frank, I understand what you are saying, I have followed all of the information having to do with ‘climate sensitivity’, it’s just that I have come across some personal analysis that says via the Galileo probe into Jupiter and Venus’s atmosphere along with what we know of our atmosphere says the climate sensitivity for carbon dioxide is fleetingly tiny. Has to do with optical depth of the pertinent lines of the infrared absorbing gases at the planetary scale but this is not a good place to get into that, it’s off topic and would drag this right back into a property of matter called mass that Willis disagrees with its importance, but I do understand it is all just calculations of observations that may very well be just natural variability mistaken as unrelated signals.
That is, better leave this for a future post.
But I did perfectly agree with most of what you were saying on the lines of the physics involved having to do with this post, must take the masses and time into account.
Upthread, someone asked me to show the lagged forcing versus the temperature. I said I’d leave it as an exercise, because I was feeling lousy. I still am, but I can’t let that stop me. Here is the requested graph
The values are lambda (sensitivity) = 0.05 °C per W/m2 (0.18°C per doubling of CO2), and tau (the time constant of the lag) = 6.5 months.
w.
Frank says:
September 23, 2013 at 1:53 am
Frank, that’s because I’m using the canonical relationship of the current (and in my opinion incorrect) climate paradigm. This is that ∆T = lambda ∆F, where F is forcing, T is temperature, and lambda is climate sensitivity.
As I tried to say up top, I don’t believe that’s how the world works … I’m just trying to show that by their terms the so-called “sensitivity” is very small.
w.
michael hammer says:
September 23, 2013 at 2:33 am
Thanks, Michael, but actually I’m not talking about feedback. Instead, I’m talking about a governed system, which is a very different critter. See my post called “It’s Not About Feedback” for a discussion of the difference.
w.
RC Saumarez says:
September 23, 2013 at 7:39 am
RC, I’m using the same method (lagging the canonical equation of ∆T = lamba ∆F) that I used to analyze the models. I got an R^2 of about 0.98 between my simple emulation and the models. And despite that actually quite amazing result, you think I need help?? … are you shooting for an R^2 of 1.5 or something?
Next, as I said above, I’m using their claims and their methods to do the analysis, so I can compare apples to apples. I have specifically said I don’t think the actual temperature works that way … so you coming along to proudly announce that the actual temperature doesn’t work that way just shows that you haven’t understood what I said … but instead of saying “I don’t understand”, you want to tell us how brilliant you are, with your PhD from a leading LSD lab or whatever it was, and offer to help me. No thanks.
Finally, you say that:
Actually, that’s not true at all. Small changes in the input data hardly affect the results at all. How do I know that? Because unlike you, I actually did the exercise, instead of just making claims … so once again, you’re operating out of your own fantasies of what’s going on, instead of actually doing what I did to find out the truth of the matter.
So you’ll excuse me if I find you pompous, insulting, and more to the point … wrong.
w.
Willis your arguments do not hold water, when it comes to volcanic eruptions and there impact or lack of impact on the climate. Read my earlier pos. In addition hundreds of studies do not agree with your study.
I guess this is what makes climate what it is, everyone having a different take on things. Time will tell in all of this.
MikeN says:
September 23, 2013 at 7:57 am
No, they say it’s half “natural variations”, a quarter solar, and a quarter volcanoes.
Here’s the bizarre part. In the last couple decades, using round numbers, the IPCC predicted about 0.4°C of warming … which hasn’t happened. So if a quarter of that (0.1°C) is volcanoes, and the recent volcanic forcing is (by their own numbers) about 0.1 W/m2, they’re saying that the climate sensitivity is 3.7° per doubling of CO2.
Of course, if that were the case we’d have seen a drop of about 3°C from Pinatubo … and I fear that I don’t see that in the records.
They just make these claims … but they don’t think them through to the end.
w.
Willis can not explain and will not explain why the earth has gone from glacial to inter glacial periods from time to time and why the climate has undergone several epsiodes of abrupt climate change in the past.
Willis is correct to point out that the IPCC is trying to say volcanic action has caused the warming to slow down, and in reality it has had nothing to do with it. That is easily seen by looking at a chart of the aerosal optical thickness for the N.H from 2005-2011. The thickness is at very low values.
Craig says:
September 23, 2013 at 1:36 pm
“Iben Browning did a lot of work on this before he died. ”
I attended two of Iben Brownings lectures where in he hypothesized colder climate due to his predicted increase in volcanic activity which I understood to be based upon planetary alignments in his theory. This was late 1980’s I believe. Very interesting guy. He said we had the Soviets fooled in the nuclear showdown since our “big cities were false targets” as we would be better off without them.
Beta Blocker says:
September 23, 2013 at 11:33 am
Beta, that’s an excellent question. I’ve been collecting evidence wherever I can, from the TAO buoys and the Argo floats and the CERES dataset, and I’ve published it all on WUWT. I’m always looking to add to that.
Regarding Thomas’s questions, the earth appears to be “bi-stable”, that is it has two different states, and it can shift from one to the other. I hold that the shift is totally explained by the Milankovic changes in the planet’s orbit, leading to a long-lasting shift in the planetary albedo. Each of the two states, however, appear to be stable, indicating that my mechanism is operating during both parts of the ice age cycles.
w.
David says:
September 23, 2013 at 1:23 pm
David, take the timescale of 100 years. Over that time, the global average surface air temperature has not varied by more than ± 0.1%. As I said above, any engineer will tell you that that is very, very good regulation.
w.
Salvatore Del Prete says:
September 23, 2013 at 2:59 pm
Salvatore, you don’t seem to understand the process of falsification. If you think that I’m wrong, then you need to point out the flaws in my logic or my math or my data.
Because simply claiming that my arguments “don’t hold water” doesn’t do it. Neither does your risible claim that there are “hundreds of studies” that disagree with me. If you think I’m wrong, first QUOTE MY WORDS that you think are wrong, and then show us, not simply claim but show us, why my words are wrong.
w.
Willis Eschenbach says:
September 23, 2013 at 3:15 pm
“David, take the timescale of 100 years. Over that time, the global average surface air temperature has not varied by more than ± 0.1%. As I said above, any engineer will tell you that that is very, very good regulation.”
w.
Short term and minor events, yes. Longer term and major events, not so much. Toba 74,000 ybp is still hypthesized by many to have cooled the climate for 1000 years and possibly started the glaciers growing due to 5 to 10 years of winter and the resultant increase in earth’s albedo. Yea, I know others disagree with this. Generally, though, I have to agree with your theory re regulation. It is one of those myriad of issues which somehow always work out to the benefit of life. Now how can you figure that? Energy levels in the atom, expansion rate of the universe, and so on, all just right. It’s the Goldilocks syndrome.
Willis you are trying to show ever so hard that volcanic forcing is much less, when past evidence shows the contrary.
For example look at the temperature data following the Mt. PINATUBO eruption from Dr. Spencer’s web-site where he shows month by mothn temp. data goiing back to 1979.
Look at what happened to the temperatures following the Mt. Pinatubo eruption, they went down in the face of an El Nino.
Why it is hard to prove what Willis wants to prove.
Each volcanic eruption is different in regards to it’s location, composition of what it ejects into the air, height/amounts of material it ejects into the air making a volcano /temperature correlation amost impossible to obtain, not to mention other climatic items acting in concert or against the volcanic climatic effects.
Willis says and it it correct in a sense( but not really) the following: a host of emergent thermostatic phenomena act quickly to cool the planet when it is to warm, and to warm it when it is to cool.
If true 100% of the time as you convey more or less; reconcile that statement with the fact the earth has had many ABRUPT climatic changes in the past, and have shifted from a glacial state to an inter glacial state many times in the past. Apparently that statement does not hold up under all circumstances for if it did the climate would never have abrupt climate swings in temperature both up and down, or vary from a glacial to an inter glacial period.
Willis you make it work out okay with the data you use, the problem is the data you are using ,like global climatic models can’t account for all the variables that are going on in the climatic system of earth, which can translate into the very percise data you suggest will happen if a volcanic eruption takes place. You don’t have all the pieces of the puzzle to make such a sure fire conclusion in my opinion.
Joe D’Aleo had a very interesting arcticle about volcanism and climate effects. Came out July 19th on icecap.com. A very different take.
Still Willis,you put in great efforts in what you do right or wrong, that I must admit.
Willis, I have been interested in ocean fertilization by dust and its effect on marine CO2 uptake, and ultimately, carbon mineralization.
Plot the 1980-2002 with Log(Dust) & Keeling and have a look at the drop in the rate that atmospheric CO2 rises. Don’t think this is a SST cooling as the oceans do not respond that quickly.
Thanks for the aerosol link, never had the monthly data before.
I would say the temperature data following the Mt.Pinatubo eruption showing a drop in world average temerature. despite an El Nino is very convincing counter evidence to what you conclude.
Again there are many studies, and to try to get an accurate picture one must look at many studies and weigh the pros and cons.
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