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
Willis, I too, am a heretic. The fact that our planet continues to be water based within a relatively narrow temperature range and its history of excursions towards an ice ball and back again seems to bear this out.
The current global warming mechanisms may be valid (though I doubt some of it) but the models completely underestimate the way our planet can restore climate stability. The climate scientists are too busy trying to defend their models to understand this.
Greg Goodman:
In your reply to me at September 22, 2013 at 11:04 am you say
For sake of clarity, I point out that the Ramanathan & Collins (R&C) effect induces cirrus not thunderstorms. They argued – initially against much opposition which their finding withstood – that when sea surface temperature reaches 305K the induced evapouration rate is so great that warm air rises to lift evapourated moisture so high that cirrus formation occurs. This cirrus sets the maximum surface temperature by reflecting sunlight so it cannot reach the surface.
The Eschenbach effect raises heat from the surface to high tropospheric altitude where it radiates to space. It starts to operate at temperatures below 305K.
They are very different – and complimentary – mechanisms.
Richard
Once again, the IPCC has an hypothesis, backed up by simple lab experiments, that the addition of certain chemicals to the atmosphere should have an effect on global temperatures. Their response when it is pointed out that the effect is not as pronounced as predicted is to say that the
science is basic and settled.
Good to see Willis that your time spent in the Old Country has not blunted your analytical skills.
“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.”
But what sets the temperature (or rather system energy content) other than the strength of the gravitational field, the mass of the atmosphere and top of atmosphere insolation ?
AGW theory relies on compositional changes altering that baseline system energy content.
Compositional changes only result in circulation adjustments which prevent a change in the baseline level hence your emergent thermostatic phenomena but globally rather than just in the tropics.
jai mitchell says:… If the energy going into that sphere containing the whole earth and all of it’s functions is more than the energy leaving that sphere then the planet is warming.
Proven counter-example of a closed system for which that is not true:
A steam engine with more heat provided doesn’t necessarily get any hotter or ’emit more heat’. It instead goes faster.
That is: The energy doesn’t need to come out – it can be converted into work. Just because you didn’t make the heat cycle with steel tubing doesn’t mean it isn’t a Carnot heat engine.
One has to ask what sets the governing mechanism and in my view it must be atmospheric pressure which is a consequence of mass alone held within a gravitational field:
http://www.newclimatemodel.com/the-setting-and-maintaining-of-earths-equilibrium-temperature/
Thanks Willis,
I’m not a scientist, so please pardon my ignorance, but in figure 4 are the two scales used equivalent? Does forcing of 4 w/m2 equal 0.8C in temperature anomaly? If so, what are the assumptions behind this analysis? Also, doesn’t figure 2 illustrate the temperature anomalies, rather than the actual surface temperatures? This seems like an important distinction which is often missed, but maybe I’m wrong.
” It is my contention that a string of thermometers along the ITCZ is all we need to tell us the direction of significant changes in climate. ”
Not necessary.
The net latitudinal position after stripping out seasonal variation is all one needs.
Towards the north pole = warming.
Towards the equator or the south pole = cooling.
It would be helpful to ascertain the neutral position first though.
Volcanic and Solar Forcing of Climate Change during the …
http://www.meteo.psu.edu/holocene/public…/Shindelletal-jclim03-preprint.pdf
This study concludes volcanic eruptions do have an effect on the climate.
In regards to the IPCC saying small volcanic eruptions caused the temperature rise to slow , they are wrong if one looks at a volcanic aerosol optical thickness graph which shows very low values since the Mt. Pinatubo eruption.
If one goes to Dr. Spencer’s website one will see a very clearly define temperature drop in global temperatures following the Mt. Pinatubo eruption in the early 1990’s. This temperature drop was despite an associated El Nino at the time, which clearly shows a large volcanic eruption will cause a substancial drop in global temperatures for a short time following the eruption.
Stephen Wilde:
It seems you have independently rediscovered the Jelbring Hypothesis.
Please google for it because there has been much debate of it over the years.
Richard
A very nice piece of work. I guess I can go back and add in the data I lopped off the beginning of the SST record to eliminate the effects of Krakatoa.
All the best
3. Impact of Volcanic Eruptions
The global annual average surface temperature response to volcanic
eruptions is cooling, resulting from increased absorption and reflection of
incoming shortwave radiation by stratospheric aerosols. Averaging all years of the
simulations together, the mean annual average cooling was -0.35 C for the
periodic Pinatubo eruption, -0.77 C for the periodic Tambora 2P eruption, -1.09
C for the periodic Tambora 3P eruption, and -0.44 C for the observed 1959-1999
The above is from the study I sent inmy previous post.
Willis says: Thanks for another great post.
Volcanic and Solar Forcing of Climate Change during the Preindustrial Era
Drew T. Shindell1,2, Gavin A. Schmidt1,2, Ron L. Miller1,3, and Michael E. Mann4
1NASA Goddard Institute for Space Studies, New York, NY 10025, USA.
2Center for Climate Systems Research, Columbia University, New York, NY
10025, USA.
3Department of Applied Physics and Applied Mathematics, Columbia University,
New York, NY 10025, USA.
4Department of Environmental Sciences, University of Virginia, Charlottesville,
VA 22902, USA.
If one wants to google the study.
If Willis is correct (and this seems very plausible based on his data) does this not mean it likely that man-made aerosols have a lower than generally assumed impact on temperature?
I also wonder about the impact of volcanic ash on ice extent and temperatures in the polar regions. There is significant evidence that man-made deposits of black carbon will increase the thermal absorption of snow and ice accelerating the melt. Would volcanic ash not have an impact there?
There might be some mileage in correlating those volcanic events with polar temperatures specifically.
“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”
I have already proposed such a scenario.
When the Earth gets warm enough for outward longwave to exceed solar incoming then there is an excess of energy going out and the system cools.
When the Earth cools so that outward longwave is less than solar incoming then there is an excess of energy coming in and the system warms.
The mediating mechanism in the atmosphere is the global convective air circulation which adjusts as necessary to maintain ToA energy balance..
The importance of the water cycle is that its heat shifting efficiency is so great that it does most of the work that would otherwise need to be done by changes in the speed of the convective circulation.
The existence of the water cycle means that the necessary adjustments need not be as violent as would otherwise be necessary.
It is atmospheric pressure which sets that top limit for ocean surface temperatures.
The evidence is that increased volcanic activity during past prolonged solar minimums enhanced the temperature declines the globe experienced at those times periods
Further the case can be made of a solar/volcanic correlation. Many studies showing increased volcanic activity being associated around solar minimum periods.
richardscourtney says:
September 22, 2013 at 11:48 am
Hi Richard.
Hans Jelbring is correct in general terms as regards his ‘Wind Driven Climate’ but I have topped and tailed the whole climate story so as to incorporate a scenario that also accommodates the ideas of Willis, the data of Bob Tisdale, the latest upper atmosphere data and many other contributions from many other commentators.
Peter Miller says:
September 22, 2013 at 11:06 am
Volcanologists recognize or suspect three or four VEI7 eruptions in the past 2000 years: Tambora (1815), Rinjani (13th century, but unconfirmed), Baekdu (969) & Taupo (180-230). The candidates for the c. 540 event, Rabaul & Ilopango, are currently rated as VEI6. I might have missed some.
“But what sets the temperature (or rather system energy content) other than the strength of the gravitational field, the mass of the atmosphere and top of atmosphere insolation ?”
That is important along with atmosphere composition. I realize that your website concludes that atmospheric composition is not important, but simulations of atmospheric columns differ from that conclusion. See hitran results in table 2: http://web.archive.org/web/20121226202653/http://www.john-daly.com/forcing/hug-barrett.htm
The important point that we can all agree on for this thread is that there are various thermostatic effects both local to the tropics and global that limit the planet’s warmth. Short term that includes convection and clouds. Long term thermostats include heat transport to the poles both by meridional flow in the atmosphere and by oceanic currents. For the latter, a good example is ice-free waters that allow more cold bottom water to form in the Arctic and flow into the Atlantic.
Cloud thermostats also limit cooling. Ice increases limit cooling as well by preventing heat loss and limiting cold bottom water formation. It’s not as if the planet is finely tuned regarding energy balance, but the thermostatic mechanisms are nonlinear and kick in more as the planet deviates from the baseline. That also determines the significance or insignificance of raised CO2 levels.
John L. Casey1
Released for world wide web (www) distribution on Monday, March 1, 2010.
[1] An independent review of historical records was performed for 350 years of global volcanic activity
Link
[Salvatore, please do not post such a huge chunk of text, I’ve replaced it with a link. We can all read, so make your point and post a link. In this, you’ve not even commented on why you posted the link. -w.]
Tom McCord says:
September 22, 2013 at 9:58 am
I suppose it’s possible. The Sato dataset apparently doesn’t go that far back. Given that Tambora lifted 25 cubic miles of stuff into the atmosphere and Krakatau in 1883 only lifted 4.5 cubic miles, Tambora could have blocked 20 W/m^2. OTOH, the SO2 output was only a third greater, so maybe only about 5 W/m^2. The biggest impact of the Year Without a Summer was at latitudes where summer freezes killed crops, so perhaps the distance to the tropical convection governor allowed for the cooling and southerly shift in the storm track that made for an “interesting” year.
Willis shoots most of that down in http://wattsupwiththat.com/2012/04/15/missing-the-missing-summer/ so your mileage may vary.
Stephen Wilde:
Thankyou for your reply to me at September 22, 2013 at 12:00 pm. However, it seems I was inadequately clear.
I was not mentioning Jelbring’s PhD thesis on wind driven climate. I was mentioning his hypothesis that any planet has a surface temperature defined by gravity and atmospheric mass (assuming an atmosphere with sufficient atmosphere which e.g. Mars lacks).
Richard
I should add that my previous comment is directed at Stephen Wilde.
Thanks Richard. I’m struggling with Readcube so I have not been able to get a good understanding of that paper yet.
It’s a shame that most of the interesting and objective climate science seems to have stopped being published around 1990.