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
Discover more from Watts Up With That?
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I thought the plan was to hide the warming in ocean depths and under ice sheets where no one could monitor it with existing taxpayer funded systems like satellites and ocean buoys.
Is it possible that the “Year Without a Summer” in 1816 was not really caused by the eruption of Mount Tambora in Indonesia after all?
Probably a good time to throw in my volcano stack plots again:
http://climategrog.wordpress.com/?attachment_id=285
They largely supports Willis’ hypothesis.
I agree that “skeptic” is too mild a term. We aren’t doubters, we’re disbelievers / dissenters / deviationists / contrarians (the term I prefer). Or “hot-air heretics.”
Again, brilliant work Willis. Thanks!
Interesting,
Just be sure you set the correct boundary conditions when looking at your thermodynamic balance. I noticed in your previous work you listed “rain” as a potential cooling mechanism. I have heard from an uneducated caller on a radio show that more lakes means global cooling (because it is cooler near the lakes)
This kind of thinking isn’t really helpful since the correct boundary conditions are set about 1/4 of a mile above the top of the atmosphere. 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.
There is no other scientific reality. You cannot put energy into an object without it warming, you cannot take energy from that object without it cooling.
With 2/3 of the planet covered by water, perhaps volcanoes’ greatest impact is the result of injecting heat into the oceans. Question here is whether this would result in net warming, or cooling (depending on location) due to positive cloud cover/precip? Any studies on this?
Don’t volcanoes also emit large quantities of CO2 into the atmosphere? Is this taken into account?
Willis – please can you explain how you translate W/m^2 into “per doubling of CO2”. The IPCC report would presumably have two separate measures, direct and indirect (ie. without and with feedbacks). Also, why the figures you quote relate to ECS not transient sensitivity (I didn’t get that bit).
TIA
Willis, I’m a little troubled by the units you’ve chosen: 0.18°C/doubling of CO2. It’s not clear what this means or where it comes from.
I presume it is converting W/m2 into some ‘carbon equivalent’ but what value is used (ie assumed) to be the effect of CO2 doubling.
If you want to use such a unit it would be good to explain what it means.
It would be interesting to do your processing for tropical and extra-tropical regions separately. I found significantly different responses and since your hypothesis is based largely on the climate response in the tropics, this is where you need to look for confirmation or falsification.
My volcano stack processing showed exactly the kind of overshoot you are referring to in the tropics but not in extra-tropical regions. The small ex-tropical effect is also temporary. Due to units I don’t know how this compares quantitatively. But in form, it is in agreement.
You may well find better correlations to the ‘small’ effect in the split analysis since the tropics would tend to reduce the correlation.
It would presumably be very little effort to use regional temp time series and re-run the scripts.
Jim S says:Don’t volcanoes also emit large quantities of CO2 into the atmosphere? Is this taken into account?
Largeness is relative. In view of what we chuck out and the natural annual carbon cycle volcanoes are a fart in the wind.
Jim S, the emissions from individual eruptions is pretty much negligible. Overall volcanoes emit around 1% of the amount from fossil fuels.
Maybe Eschenbach has written about it before, but I’m a bit confused on how he can reconcile “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” with the existence of ice age cycles. Whatever thermostat the Earth has doesn’t seem all that good.
theyouk says:With 2/3 of the planet covered by water, perhaps volcanoes’ greatest impact is the result of injecting heat into the oceans.
Look at my volcano stack graphs. They are interlinked and have some commentary. I worked on SST rather than land+sea indices but I did comment of the possible impact of land/sea ratios and the way land rate of change is twice ocean rate of change (dT/dt) and how this affects NH / SH differences.
theyouk:
At September 22, 2013 at 10:16 am you ask
What mechanism would cause volcanos to “inject heat into the ocean”?
There can be no studies of something which is not known to exist.
And the “injection” could not happen in the warm tropics because there is a maximum sea surface temperature of 305K. When the sea surface is at that maximum temperature then additional heating (from any cause) results in the ocean COOLING.
The effect was first reported by Ramanathan & Collins in 1991.
Their paper is Ramanathan v & Collins W, ‘Thermodynamic regulation of ocean warming by cirrus clouds deduced from observations of the 1987 El Niño’, Nature 351, 27 – 32 (02 May 1991) doi:10.1038/351027a0
Its Abstract says
Observations made during the 1987 El Niño show that in the upper range of sea surface temperatures, the greenhouse effect increases with surface temperature at a rate which exceeds the rate at which radiation is being emitted from the surface. In response to this ‘super greenhouse effect’, highly reflective cirrus clouds are produced which act like a thermostat shielding the ocean from solar radiation. The regulatory effect of these cirrus clouds may limit sea surface temperatures to less than 305 K.
In other words, the effect they found is that increased heating of tropical ocean increases evapouration to increase cover by cirrus clouds which shield the surface from solar heating. This shielding sets a limit of 305K to maximum surface temperature.
But clouds don’t stay in one place. Therefore, when a region of the surface has temperature of 305K, then additional heating (from any cause) increases cirrus clouds which spread to shield surrounding regions. Thus, the effect does not merely set a maximum temperature: it induces a drop in surface temperature of the surrounding ocean regions when surface heating is increased.
The R&C Effect can induce a fall in surface temperature when surface heating is increased. And the Eschenbach Effect does that, too.
As Willis says, these effects – and any similar effects – would provide a homeostatic control to global temperature.
Richard
The large climate sensitivities claimed by IPCC not only give large negative temperature excursions but also very long times to return to normal. (See for example Lindzen http://link.springer.com/article/10.1140/epjp/i2012-12052-8#page-1). This must be true because climate senitivity is basically the climatic relaxation time divided by the effective specific heat of the climate system. So if IPCC were right, we still have not recovered from Krakatoa (1883) and Katmai (1912), not to mention Pinatubo (1992). In fact the IPCC climate sensitivity is so large that a normal century’s eruptions would keep the earth about a deg C cooler than otherwise and we would never be far from a volcanic “winter” from a few major eruptions.
This alone should raise eyebrows about the plausibility of the IPCC values of climate sensitivity.
Thomas: ” Whatever thermostat the Earth has doesn’t seem all that good.”
what happens at glaciation and deglaciation is clearly different from what happens in between. There is apparently two stable states ( attractors ) for the climate system. A positive feedback seems to make it snap form one state to the other. We don’t really know what triggers the change-over.
Assuming Willis is basically correct there are limits to the tropical storms range as a feedback mechanism. It cannot go beyond totally clear skies or fully cloud covered tropics. May be when it hits the rails the climate state flips?
I don’t see glaciation as being a major argument against what Willis is proposing.
‘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.’
I think you will find plenty of agreement there. The statement above seems to mirror a similar point made by Dr. Richard Lindzen. I can’t recall his exact wording but he seemed to say, that in the end, Global Warming distilled down to a philosophical question: Does one believe that a long running natural system amplify perturbations, or would it minimize perturbations?
I think the answer is obvious simply from the description, ‘long running natural system.’ How could the Earth possibly have been a long running natural system if it stampedes away into nightmare land with every little deviation away from what nobody knows is really the norm? I think the planet has a lot more things to worry about then us little humans. And I think we have a lot more things to worry about too. And to take joy in. Welcome back from your trip Willis Eschenbach. I took joy in it.
While volcanos cause cooling initially, some may actually cause warming afterwards.
Have a look at the Temperature of the lower statosphere ftp://ftp.ssmi.com/msu/graphics/tls/plots/rss_ts_channel_tls_global_land_and_sea_v03_3.png
You can see a clear boom and bust signal, probably due to the SO2 stripping H2O out of the stratosphere from where it cannot be easily replenished.
Of course multidecadal volcanic cooling of the stratosphere may have nothing to do with tropospheric temp, but its hard to know when nobody has ever looked.
Tom McCord says:
September 22, 2013 at 9:58 am
IMO evidence supports the contention that The Year Without a Summer was indeed caused by Tambora, with the effects amplified by having occurred during the already cold-stressed Dalton Sunspot Minimum.
Earlier in the Little Ice Age, the Pacific volcano Kuwae had similar effects after its c. 1452 eruption, shortly before the Spoerer Minimum. Also, an eruption of Huaynaputina in Peru is blamed for the severe Russian famine of 1601–03. The 1783 eruption of Laki in Iceland caused thousands of deaths in Europe. The latter two events fell before & after the Maunder Minimum.
richardscourtney says: … these effects – and any similar effects – would provide a homeostatic control to global temperature.
Thanks, Richard, I was not aware of that paper. Thunderstorms have more to do with convection and evaporation the “super greenhouse effect” but I suppose they had to boost AGW keyword count in order to get published.
the article is available through ReadCube (which is only just above unusable in my browser, I’ll perisist)
http://www.readcube.com/articles/10.1038/351027a0?locale=en
Thomas says:
September 22, 2013 at 10:30 am
During glacial epochs, climate seems to have two (or three) phases, ie long glacial & shorter interglacial, with possibly an even colder phase within the glacial, associated with Heinrich Events. The Last Glacial Maximum is an instance of the possible third “steady state”, shorter than interglacials & perhaps just extra-cold D-O events.
In all probability, the really huge volcanic eruptions of the past 2,000 years – in 542 and 1816 – did have a significant effect on temperature, but these were eruptions an order of magnitude greater than the Pinatubo one in 1992
“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.”
Well, of course it is invisible and it will remain so until some climate scientists go into the natural environment, maybe the Virgin Islands, and start measuring the thermostatic control phenomena. Because climate scientists are so very averse to empirical research, they are not going to do the necessary work, at least not this generation of climate scientists.
Maybe the 17 yr pause in global warming is due to a time-warp teleconnection to past volcanic eruptions. Their cooling was just in the pipeline until recently.
Willis, once a mere skeptic myself I became a climate heretic by simply reading your simple and elegant articles on homeostatic mechanisms for resisting changes up or down in earth temperature. Your demonstrating that there is an upper limit to SST of ~31C from the data clinched it for me. I came at the stability of climate from the long geologist’s view in which global temperature fluctuations over hundreds of millions of years has an amplitude of only 3-5K! If I now understand your ideas, the upper limit for SST is a sharp 31C – the sea surface won’t surpass this because of the governor mechanism. The lower limit is less firm in that with all the thunder clouds gone with cooling, heating depends essentially on insolation which may be insufficient to bring it back up toward 31C (Milankovitch cycles, and other). This would mean a slowing of the tropical – polar thermal exchange causing greater ice accumulation in a cooling system. 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.
I think the groundwork you have laid will lead to the slam dunk physics of the climate system. An answer to the question why specifically 31C is the upper limit of SST will open a floodgate of understanding. Yes, to be a skeptic is good for science and good fun where you meet the interesting proportion of fellow humans. But to blow past it all and put forth an entirely new paradigm is even more exciting and interesting. There will be a lot of people who won’t like you but that is a good way to help winnow out those on whom you shouldn’t waste too much time.