Guest Post by Willis Eschenbach
I got to thinking that the eruption of Mount Pinatubo should provide a good test case for my theory that changes in albedo help regulate the temperature and keep it within a narrow range. When a big volcano erupts, it throws both black and reflective particles and aerosols high into the stratosphere. As a result, the albedo (reflectivity) and the shortwave absorption of the stratosphere both increase, available solar energy decreases, and the planet cools. By that theory, available solar energy (after albedo) should show a dip after the eruption followed by a recovery to pre-eruption values.
I have demonstrated in the post cited above and elsewhere that cloud albedo varies with temperature in order to prevent excessive heating or cooling. As a result, if my hypothesis is correct, we should see a more complex and different reaction to the eruption. We should see a planetary albedo response to Pinatubo that restores the temperature. If there is a temperature governing mechanism in play, we would expect the change in albedo to provide extra energy to counteract the cooling effect of the eruption. So we’d expect the available energy to overshoot, providing more energy than normal, until the balance is restored.
So I plotted up the change in available solar energy, which I calculated as total solar irradiance TSI * (1 – albedo), for the period 1984-1998. I also plotted the global average temperature for the period, converted to a blackbody equivalent temperature in watts per square metre. The results are shown in Figure 1.
Figure 1. Anomaly in solar energy available after albedo reflection (yellow), and global equivalent blackbody surface temperature anomaly (dark red). Date of the Pinatubo eruption is shown in green.
How do these observations support the idea that there is an albedo-based temperature regulating mechanism?
Look at what actually occurred after the eruption. The amount of solar energy began rising, and continued to rise in opposition to the falling temperatures. It remained high, significantly higher than most of the record, until the temperatures started to rise in 1994. Only after temperatures had returned to pre-eruption levels did the amount of solar energy drop back down.
This is precisely the response that would be expected from a governing mechanism involving the albedo. It would let more energy into the system to counteract the volcanic cooling, and would continue doing so until the temperature was restored.
So I hold that this provides clear visual evidence that an albedo-based temperature compensating mechanism does exist. I also say that this mechanism explains the poor performance of the GISS climate model, whose predictions of Pinatubo I discussed here and here. Because it does not include any albedo-based compensatory mechanism, the GISS model predicted a much larger temperature drop than actually occurred.
w.
DATA NOTES:
The albedo data is from Long-term global distribution of Earth’s shortwave radiation budget at the top of atmosphere (PDF), N. Hatzianastassiou et al., Figure 8(c). Temperature data is from the HadCRUT3 anomaly dataset and the HadCRUT absolute temperature dataset. Absolute temperatures plus anomalies were first converted to the equivalent blackbody temperature in watts per square metre using the Stefan-Boltzmann equation. Both datasets then had their monthly averages removed before graphing.
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@- Stephen Wilde says:
“Thus whilst the sun was more active the stratosphere generally cooled with more poleward/zonal jets but now that the sun is less active we seem to be seeing the stratosphere no longer cooling and perhaps beginning to warm with more equatorward/meridional jets.”
The long-term cooling observed in the stratosphere is not obviously correlated with any solar changes, which have been too small to have such an effect. Neither is there clear evidence of stratospheric warming – unless you have a link that shows otherwise!
The decades long trend in stratospheric cooling is a product of the change in two key components of the stratosphere with major thermal effects. The increase in CO2 increases cooling and the decrease in ozone reduces warming.
Both of course are anthropogenic changes.
Thanks Willis for the explanation of the phenomenon: from volcanic plume -increased albedo-cooling-reduces the cloud cover after for a period after the sky has cleared permitting more sunshine in.
Jim Masterson says:
August 22, 2011 at 2:46 pm
Why some volcanoes have the cooling effect, others not. It takes an explosive event strong enough and voluminous enough to project the plume up into the stratosphere. If it doesn’t reach the stratosphere, it is dispersed in the lower-intermediate atmosphere and settles to the surface more quickly. Mount St Helens had a strong local effect to be sure but not a significant global one.
One of these days we’re going to get a volcanic eruption that cools the earth enough to spell the end of the Holocene interglacial. The conditions are ripe. Interglacial is already 2000 years older than average of 10,000 years. Axial precession is halfway to its least amount of tilt and orbital precession has closest approach to sun just three weeks short of middle of winter. Both parameters are and will continue for several thousand years moving towards point of least NH difference between summer and winter temperatures which is what gives ice & snow the upper hand.
We’re sitting ducks. And environmental whackos want to help it along by slowing down anthropogenic warming and thus decreasing whatever safety margin we have against a volcanic eruption ending the interglacial period. Lunatics…
.
Stephen Wilde says:
August 22, 2011 at 3:13 pm
Stephen, that’s an intriguing hypothesis. Do you have any citations or further reading on that?
w.
izen says:
August 23, 2011 at 2:46 am
Thanks, izen. I agree with you on both counts. As the satellite shows, what we have is a very odd looking record for which I’ve never heard an explanation.
The odd thing about the stratosphere is that it is a series of stable plateaus, punctuated by volcanic eruptions. After each eruption, a new, lower plateau has started up.
If the cause of the decline were in fact the increase in CO2 and the decrease in ozone as you say, then what is the explanation for the level plateaus between the eruptions?
Alternatively, why would the effects of the CO2 and ozone only affect the temperature immediately after the eruptions?
I don’t have answers to those questions. Until I do, I’m unwilling to ascribe causality unless it includes an explanation for the odd looking historical record.
Regards,
w.
“Stephen, that’s an intriguing hypothesis. Do you have any citations or further reading on that?”
Sure, Willis, but it is contentious at present. Anyway, here you go:
http://www.irishweatheronline.com/news/environment/wilde-weather/the-sun-could-control-earths-temperature/290.html
I’ve been posting the link regularly but with little response for whatever reason.
“The long-term cooling observed in the stratosphere is not obviously correlated with any solar changes, which have been too small to have such an effect. Neither is there clear evidence of stratospheric warming – unless you have a link that shows otherwise!”
Your wish is my command:
http://www.jstage.jst.go.jp/article/sola/5/0/53/_pdf
“The evidence for the cooling trend in the stratosphere may need to be revisited. This study presents evidence that the stratosphere has been slightly warming since 1996.”
“The odd thing about the stratosphere is that it is a series of stable plateaus, punctuated by volcanic eruptions. After each eruption, a new, lower plateau has started up”
That’s not the way it looks to me. I see a downward trend up to about 1996 disrupted by two volcanic eruptions along the way and a cessation of cooling from the mid 90s when solar cycle 23 started to fade from its peak and now early signs of a recovery.
Stephen Wilde says:
August 26, 2011 at 12:59 pm
Thanks, Stephen. That’s one of the problems with only having such a short satellite record of the temperatures. When you remove the volcanic sections, we’re left with three short records. None of the three have a trend which is significantly different from zero, with the first one way too short to signify anything.
However, as you point out, it could also be interpreted as a decline from the start of the record to about the middle of the record, followed by the second half of the record which has no trend at all.
Either one is odd. And a vague reference to solar cycles doesn’t explain what you describe as a fifteen-year steady decrease (with volcanic punctuation), followed by fifteen years of dead-level no-trend temperatures.
So under each interpretation (either steady decline or plateaus for half the record, followed by level temperatures for the second half of the record) the stratospheric temperature record does not have an obvious explanation.
All the best,
w.
I think we need to look at possible alternative explanations for a decline for 15 years and there are two competing scenarios:
i) Human emissions of CO2 causing a cooling of the stratosphere by reducing upward energy loss as proposed by AGW theory.
ii) An active sun causing a cooler stratosphere rather than a warmer stratosphere which is the opposite of the conventional wisdom as proposed by me alone as far as I know (before Joanna Haigh said we might have to reverse the usual sign of solar effects on the atmosphere).
However i) does not explain the plateau whereas ii) does because the cessation of stratospheric cooling occurred as the level of solar activity declined after the peak of cycle 23.
The shortness of the record is indeed a problem but it may well be that so far the quiet sun has only had long enough to stop the stratospheric cooling trend with a warming trend still to become established if the sun remains quiet long enough.Looking at single cycles is not enough. Looking at groups of successive cycles is better. Best is looking at solar variability from LIA to date (1600 to 2000).
The flatness of the trend in the period between the two eruptions is odd but may simply be a side effect of the two eruptions occurring so close together.It may be the case that the natural trend has to play catchup for a while after the effects of such eruptions.
The test will be what happens to stratospheric temperatures over the next few years if the sun stays quiet.
The importance of stratospheric temperatures is that they control the height of the tropopause which in turn affects the surface pressure distribution globally. I suspect that a warming troposphere at a time of active sun has a cooler stratosphere and more poleward/zonal mid latitude jets letting more energy into the oceans.A cooling troposphere at a time of less active sun has a warmer stratosphere and more equatorward/meridional jets letting less energy into the oceans.
I know that is contrary to existing climatology but it is the only scenario that fits observations without the need to invoke a human influence from more CO2. That anthropogenic scenario is dead because the stratosphere stopped cooling despite continuing increases in emissions and global CO2 levels.
I have the only hypothesis currently available which fits the observations so well.
Stephen;
iii) the H0 is that the surface record is fudged, and the actuality matches the stratospheric pattern, not the accepted curves (especially since The Great Dying of the Thermometers circa 1990.)