## The Climate Sensitivity According to Volcanic Eruptions

According to the theory of global warming, anything that changes the radiative energy balance of the Earth will cause a change in temperature that is correlated to the change of energy.  The “consensus” is that a doubling of CO2 in the atmosphere will increase the energy at the surface by 3.7 W/m2.  This additional energy will increase the temperature of the Earth by 3 °C.

So in this case, the climate sensitivity is described as temperature impact as a result of the doubling of CO2 in the atmosphere.  In proper scientific form the climate sensitivity is the change in temperature as a result of a change in energy.

Climate Sensitivity = delta T / Delta E  (K/(W/m2))

This form is far more useful because it can be applied to situations other than changes in CO2 level.  Since I am one of the few that use this form I always give the conversions to CO2 doubling.  For the case of doubling causing a temperature increase of 3 °C.

CO2 doubling to cause a 3 °C increase =  0.81 (K/(Wm2))  = (3 °C / 3.7 W/m2)

With that basic information out of the way it is time to tackle the task of estimating the climate sensitivity from the two very large volcanic eruptions that have happened in the past 130 years.  They are the eruption of Mt. Pinatubo and Krakatoa.

Since Mt. Pinatubo happened in 1991 there is much better resolution data available.  This includes measurements of the change in surface energy from the sun and of global temperature.  Then I will take the range of climate sensitivity and use that to estimate the change in solar forcing caused by Krakatoa and compare to the what is thought to have happened as a result of the eruption of Krakatoa.

I will use the normal global value of solar insolation determined in Trenberth 2008 as the normal amount of energy that reaches the surface of the Earth.  This is stated as 161 W/m2.  The percentage drop in solar energy will be from that.  For instance a 1% decrease in surface energy will be a drop of 1.61 W/m2.

The measured difference in surface energy by the NOAA Climate Monitoring and Diagnostics Laboratory in Boulder, Colorado was a 2-4 % drop in total solar energy.  This corresponds to a change of 3.2-6.4 W/m2.  This is of a comparable scale to the proposed increase in energy associated with a doubling to almost a quadrupling of CO2 in the atmosphere.

The global effect on temperature depends on what method you use.  The greater the temperature response, the greater the climate sensitivity would be.  The methods that showed the greatest temperature change were the two satellite methods.  The average drop in temperature was 0.285 C and the peak was 0.5C.  I will estimate the sensitivity for both of those temperatures.

Climate Sensitivity to Mt. Pinatubo forcing using the annual satellite temperature change.

The greatest sensitivity estimate is that of a 2% reduction in energy.  In that case the climate sensitivity is 0.3 °C for a doubling of CO2.  That is 10x lower than the one generally stated by the IPCC.  If the mid-range value for the decrease in energy is used, the increase in temperature that would result from a doubling of CO2 would be 0.22 °C.  Once again the climate shows it is FAR less sensitive than what the warmists estimate it to be.

If the peak temperature drop is used, the results are as follows:

Climate Sensitivity to Mt. Pinatubo forcing using the peak monthly satellite temperature change.

The maximum sensitivity is once again with the minimum change in energy at is ~0.6 °C/doubling.  Once again that is much, much less than the IPCC estimate, even for the peak month drop in temperature.

I will not bother to use the results of the station temperature change as they are substantially lower than the results of the satellite temperature change.  I will take one additional step and estimate the change in temperature using the 3 °C /doubling.

Temperature change estimate using the IPCC estimate for climate sensitivity.

In this case the change in global temperature would have been on the order of 2.6 – 5.2 °C.  This is of course very comparable to their estimate for what the temperature will be in the year 2100.  That is because the forcing effect of eruption of Mt. Pinatubo is comparable to their estimate to the forcing for a doubling of CO2.

The range of climate sensitivities I will use for the Krakatoa eruption will be 0.059 – 0.155 (K/(Wm2)) and I will throw in the IPCC value of 0.81  (K/(Wm2)) for good measure.  That way it will be clear just how far out of whack that high estimate of climate sensitivity is.

The commonly used drop in global temperature associated with Krakatoa is 1.2 °C.  The problem is that the global temperature records do not show that in any way.  The CRU, GHCN and such show no evidence of a drop like that.  Mass, Portman 1989 provide an estimate of a drop of 0.5 °C.  So I will use both the 0.5 °C and the 1.2 °C as the change in temperature for the eruption of Krakatoa.

Estimating the % change in surface energy for the 1883 Krakatoa Eruption using the Mt. Pinatubo determined climate sensitivities. Using the low estimate for drop in temperature.

Estimating the % change in surface energy for the 1883 Krakatoa Eruption using the Mt. Pinatubo determined climate sensitivities. Using the high estimate for drop in temperature.

For the Pinatubo climate sensitivity estimates the change in surface energy for the two changes in global temperature is 2-12.6 %.  This is a very wide change in energy, but the IPCC sensitivity estimate is 0.4-0.9% change in surface energy.  That is far less than what was measured for the smaller eruption of Mt. Pinatubo.

The estimates for Krakatoa are that the total solar energy decrease for the Earth’s surface was ~10%.  This would tend to support that the temperature drop was closer to the -1.2 °C and the climate sensitivity is on the low side of 0.2-0.4 °C / doubling of CO2.

Once again the Earth’s response to significant events results in a lower climate sensitivity than what the IPCC uses.  Note that a 10% reduction in energy to the surface would drop the total energy by 16.1 W/m2.  This compares to the change in proposed change of forcing of 1.1-1.4 W/m2 for the change in CO2 from 300-315 ppm to the current 391 ppm.

Krakatoa induced at least a 14X change in energy and that at most caused a 1.2 °C reduction in temperature.  This is more evidence that the IPCC estimate of climate sensitivity is grossly exaggerated.

_______________________________

Update:

I found another source that gave slightly different values for Mt. Pinatubo.  It gave the change in energy at a magnitude of 2.7 W/m2.  That is comparable to 1.7% of the normal surface energy.  The same source puts the cooling at 0.5-0.7 °C.  So using that fixed drop in energy and the range of temperature changes that were observed, the following climate sensitivities were determined.

USGS and ERBE source for determining the climate sensitivity.

Even in this case the climate sensitivity is far less than the IPCC value by at least 3x.  Even with the minimum amount of measured energy change and the maximum temperature change the climate sensitivity is still more than 3 times smaller than the “consensus” sensitivity.  No sensitivity determined from volcanic eruptions shows a sensitivity for doubling of CO2 to exceed even 1 °C.

It should also be noted that the NOAA estimate (2-4%) was comparable to the ERBE observed (1.7%) decrease in solar energy.  Both of these vales significantly exceed the proposed forcing associated with the increased CO2 levels.  Study of the forcing effects of the volcanic eruptions provide strong evidence that the IPCC climate sensitivity is grossly exaggerated.

Offline source of Krakatoa insolation reduction:  Wexler, H.; ‚On the effects of volcanic dust on insulation and weather’, in: Bulletin American Meteorological Society, Vol. 32, No. 1, January 1951, pp. 10-15.

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## This post has 30 comments

1. In 1980, US SO2 Emissions from power plant type sources was 17 million tons per year.

By 2009 those same sources were only releasing 5.7 million tons of SO2.

http://www.epa.gov/airmarkets/progress/ARP09_4.html

My Pinatubo cooled the earth with a release of 20 million tons of SO2.

The EP clean air act/acid rain program should be responsbile for several “negative pinatubo’s” — the temperature should have gone up over .5C thanks to cleaner air.

And that is just US efforts to clean the air.

2. Mar 27th 2011

The IPCC is assuming that the Earth is radiating at 255 K,
and calculating the effect a 3.7 watt increase would have on a 255 K blackbody. In effect they’re computing what would happen if the flux from the sun increased by 3.7 watts per square meter and the earth’s greenhouse magnified that additional 3.7 watts by the same factor that the original 240 watts per square meter for a 255 K body is magnified to give a 15 C surface.

As this paper points out,

http://multi-science.metapress.com/content/8r0352171238x3v4/

stabilize at the same 240 watts per square meter as it does now, and
the climate sensitivity should be computed for a 288 K body radiating at 390.7 wsm., or using Trenbeth’s figures, giving 492 watts at the surface, 102 of which is in the latent heat of vaporization and in convection, and plugging those into Boltzmann’s T proportional to the 4th root of radiation formula, and you get an even smaller sensitivity

3. Mar 27th 2011

Hi TIS,

3°C for a doubling of CO2 is the transient climate sensitivity, which is defined as the average temperature response over a twenty year period of CO2 doubling. The other kind of sensitivity, equilibrium climate sensitivity, is twice as high but it takes thousands of years to get there.

The negative forcing effects of a large volcanic eruption are sustained for, at the very most, 2 years (aerosol residence time for the huge Pinatubo eruption was just over 2 years). This means you need to multiply your Pinatubo climate sensitivity figures by 10 to come up with comparable 20-year transient climate sensitivity figures.

If your Pinatubo figures are multiplied by 10 they become 2-4°C per doubling of CO2. That’s in exact agreement with what IPCC says. Congratulations!

I think the study you linked to, that mentions negative forcings of 2.7 W/m², is only referring to the month of August 1991, two months after the June 15 eruption. It’s unlikely that forcing was sustained for 2 years. Aerosols are slowly precipitated out of the atmosphere after an eruption stops so the negative forcing drops to near zero after 2 years.

It’s been empirically shown in laboratory tests that doubling CO2 has a forcing of 3.7 W/m² (as you said) and that this amount of forcing leads to 1.2°C of warming. This has been known since the 19th century and there’s no dispute about this within scientific circles (even “skeptic” scientists agree). When you calculate a climate sensitivity less than 1.2°C, either you did something wrong or there are some very powerful negative feedbacks at work that no one has been able to identify.

4. Mar 27th 2011

And Bruce’s comment above is quite correct above. Human emissions of SO2 (sulfur dioxide) were previously masking the global warming signal from 1940 to 1970. Clear air legislation in the sixties and thereafter led to a drop in SO2 emissions ever since. The warming of the climate wasn’t caused by their removal – their cooling effect was removed so that we could see what was previously hidden.

5. Mar 27th 2011

edit

And Bruce’s comment above is quite correct. Human emissions of SO2 (sulfur dioxide) were previously masking the global warming signal from 1940 to 1970. Clean air legislation in the sixties and thereafter has led to a drop in SO2 emissions ever since. The warming of the climate wasn’t caused by their removal – their cooling effect was removed so that we could see what was previously hidden.

6. Mar 27th 2011

SO2 emissions in the troposphere are much, much larger than 20 million tons. The result of SO2 in the troposphere is irrelevant as its residence time is very short due to the high water vapor content. SO2 in the stratosphere is significant because of its long residence time.

That is why SO2 in the stratosphere has a noticeable impact and tropospheric emissions do not.

7. Mar 27th 2011

Sound,

Transient has nothing to do with a volcanic eruption. Transient has to do with steady increases in CO2 concentrations (typically at 1%) a year and the results of the GCM’s in that case.

Step function changes have nothing to do with the transient case. That makes them ideal to determine climate sensitivity. There is no basis for multiplying a 1 year response by the 20 year practice in GCM modelling. Might as well multiply by a 10,000 equilibrium case and using that as reality.

This is one of the more frustrating things is people keep ignoring real world response and try to fit everything into the GCM response. The Earth shows a response to impulse events like volcano’s.

Ignoring the results of such events because they don’t fit an expectation is not the scientific method. Had the results shown higher climate sensitivity, I would have still put the article together.

The temperature response follows the aerosol concentration. The only time lag is the time it takes for the aerosols to spread. Compare the UAH global temperature to the Hawaii transmission.

http://pubs.usgs.gov/pinatubo/self/fig9.gif

8. Mar 27th 2011

Alan,

http://theinconvenientskeptic.com/2011/03/time-lag-and-the-moons-surface/

A change in forcing in that case makes little difference, but it also has little bearing in this situation. The Earth is a very different beast.

This is why I look for impulse events and look at the Earth’s response to them. Forget GCM’s and theoretical models.

I will look at the blackbox response to an input and determine the control routine from that.

http://en.wikipedia.org/wiki/Black_box_%28systems%29

9. Mar 27th 2011

I’ve seen the reference to the moon’s surface. Obviously the moon and earth are not blackbodies, but I think the back radiation still applies. You just have to throw in an additional factor – Newton’s law of cooling- to get an adjusted rate.

10. Mar 27th 2011

TIS: “There is no basis for multiplying a 1 year response by the 20 year practice in GCM modelling.”

Nevertheless, whether you or I agree with the methodology used, this is what your opponents at IPCC did, and this is the only difference between your and their calculations. You did not determine a new climate sensitivity figure; you just confirmed theirs, though you choose to express yours over a much shorter time frame.

Now if you want to argue the full effect of any forcing is nearly instantaneous and the duration that the forcing is sustained has no bearing on the final effect, then you would have a unique view and evidence for a much lower climate sensitivity figure. But this is counter to common sense. Even a small pot of water doesn’t warm up to its new temperature as soon as the burner under it is dialled up and it stops warming when the burner is dialled down again without necessarily having yet reached the original target equilibrium temperature. It takes a couple decades to heat up a whole world when the burner is just being dialled up by 0.9 W/m² (the TOA imbalance).

11. “Human emissions of SO2 (sulfur dioxide) were previously masking the global warming signal from 1940 to 1970.”

What global warming signal?

“Clean air legislation in the sixties and thereafter has led to a drop in SO2 emissions ever since.”

Most of the cleaning of air took place after the acid rain scare, and really got going in 1990.

http://en.wikipedia.org/?title=Acid_rain

12. Mar 27th 2011

John,

I believe the “codex” that you may require to interpret the “confusing” questions that come your way is Gilbert M. Plass. Back in the day before James Hansen got his gig at NASA, a very brilliant scientist/engineer managed to work on a Theory of Carbon Dioxide beyond Tyndall et al. I find the theory far more plausible in 1959 than any other period. I am quite sure it have a major influence on Jim, Al’s earth science professor and of course Gavin Schmidt.

Otherwise, the arbitrary movements to orders of magnitude will continue to be common-place.

Other than that, I have been “intuitively” saying for years, the sensitivity would be and order of magnitude of 0.1-1 degrees per doubling. IF there were a way to remove particulate matter, you might be able to get Cs to 3.7, but even then, that is a stretch.

I second your voice on the GCMs. GCMs are a *tool* NOT an experiment. They help you look in an area for an experiment, nothing less, nothing more. I have listened to silly people tell me a physical issue occurring was incorrect because the CFD model did not have that way.

Nice article!

13. As for residence time in the atmosphere, SO2 also causes clouds to reflect more sunlight:

“At current production levels, human-made sulfate aerosols are thought to outweigh the naturally produced sulfate aerosols. The concentration of aerosols is highest in the northern hemisphere where industrial activity is centered. The sulfate aerosols absorb no sunlight but they reflect it, thereby reducing the amount of sunlight reaching the Earth’s surface. Sulfate aerosols are believed to survive in the atmosphere for about 3-5 days.

The sulfate aerosols also enter clouds where they cause the number of cloud droplets to increase but make the droplet sizes smaller.

The net effect is to make the clouds reflect more sunlight than they would without the presence of the sulfate aerosols.

Pollution from the stacks of ships at sea has been seen to modify the low-lying clouds above them. These changes in the cloud droplets, due to the sulfate aerosols from the ships, have been seen in pictures from weather satellites as a track through a layer of clouds.

In addition to making the clouds more reflective, it is also believed that the additional aerosols cause polluted clouds to last longer and reflect more sunlight than non-polluted clouds.”

http://www.nasa.gov/centers/langley/news/factsheets/Aerosols_prt.htm

14. Mar 27th 2011

Bruce,

There’s lots of talk about AGW but we sometimes forget about AGC (C=Cooling). This abnormal condition no long exists. The industrialization of China since the late 1990s and the pollution from its new factories might partially explain the slight reduction in the warming rate over the recent decade but it’s just one of several factors.

The industrial boom that began with WWII and continued well into the 1960’s contributed a lot of aerosols (smoke, soot, sulfur, sulfates, SO2, dust, etc.) to the atmosphere along with a lot of CO2. Aerosols have an immediate cooling effect while the warming effect of CO2 and some aerosols (NOx) lags by 20-30 years. The effect of most aerosols diminishes after a few years as they are washed out of the atmosphere provided they aren’t replenished (as happened when pollution restrictions were adopted). This process compares very much to a major volcanic eruption which introduces aerosols that cool the Earth for a couple years but which also introduces CO2 that causes some warming later.

In December 1952 the “Great Smog” came to London, England. London had always been well-known for its “pea soup” fogs, but this time it killed 4,000 people in four days, with another 8,000 to 12,000 dying in the following weeks and months. This led to the Clean Air Act of 1956, and over time the pea soup fogs went away. This sort of legislation spread widely once the danger was recognized with most western nations having implemented legislation by 1970. Pollution was reduced and a strong warming trend started in the 1970s, which continues even today.

These events occurred long before the acid rain cleanup of the 1990s. For example, all cars have had catalytic converters since 1975. These devices reduce engine pollutants by about 90%. Unleaded gasoline had to be introduced before they could be used. This just shows how much things can change when people get motivated and there aren’t skeptics around to slow things down.

http://en.wikipedia.org/wiki/Great_Smog

15. IMHO, the trouble with trying to determine a climate sensitivity is the assumption that every else has stayed static. Just look up global dimming and brightening. The system was not static in the 1990s. After an early brightening in the 1920-1940s, dimming occurred until about 1980 and then brightening started again in 1990.

Mt. Pintabu might cooled the earth more than some think because brightening caused more sunshine hours which was trying to warm the planet in the 1990s.

http://www.agu.org/pubs/crossref/2009/2008JD011470.shtml

http://meetingorganizer.copernicus.org/EGU2010/EGU2010-2869.pdf

16. Mar 28th 2011

Bruce,

That the system is dynamic is precisely the reason why volcanic eruptions are useful to estimate climate sensitivity.

They provide a single impulse that causes a measurable global effect within 5 months. Nothing else matches volcanic eruptions for this type opportunity. Regardless of other factors (I have read little about dimming), the impulse change from a volcanic eruption is a useful real world case to observe the impact of a change in forcing.

17. Mar 28th 2011

Sound,

Two major problems with your argument about my method supporting higher sensitivity.

1st – Where is the evidence that they got the higher result?

2nd – Using the CRU/GISS/GHCN data gives even lower climate sensitivity. UAH/RSS provided the clear global signal. Using the station methods gives a climate sensitivity 0.16C for a doubling of CO2.

I would like to see the paper of someone using the GHCN data to prove that the eruption of Pinatubo is evidence for high climate sensitivity. Truly that would be an entertaining read, but it isn’t possible.

18. Mar 28th 2011

TIS,

Here are links to a few peer-reviewed studies providing the evidence you requested. They all used the Mt Pinatubo eruption to estimate climate sensitivity (CS). This is just what I could find in 10 minutes of searching so they might not be the best examples from the 678 articles available on this topic. I don’t have time to read each one for you.
___________________________

CS = 1.4 to 7.7 degrees

“We derive joint probability density distributions for three key uncertain properties of the climate system, using an optimal fingerprinting approach to compare simulations of an intermediate complexity climate model with three distinct diagnostics of recent climate observations. On the basis of the marginal probability distributions, the 5 to 95% confidence intervals are 1.4 to 7.7 kelvin for climate sensitivity and −0.30 to −0.95 watt per square meter for the net aerosol forcing.”

http://www.sciencemag.org/content/295/5552/113.short
___________________________

CS = 1.0 to 4.1 degrees

“these results indicate that the Pinatubo year’s climate response is not the same as the longer term response … 1.0–4.1-K range for the equilibrium warming due to a doubling of carbon dioxide.”

http://journals.ametsoc.org/doi/pdf/10.1175/JCLI3611.1
___________________________

CS = 1.5 to 4 degrees (from a study by highly respected Drs. Wigley, Ammann and Santer)

A study to “obtain an improved estimate of the underlying response of 20th century global-mean temperature response to volcanic forcing”.

“Comparisons of observed and modeled coolings after the eruptions of Agung, El Chichon and Pinatubo give implied climate sensitivities that are consistent with the IPCC range of 1.5–4.5oC equilibrium warming for 2xCO2. The cooling associated with Pinatubo appears to require a sensitivity above the IPCC lower bound of 1.5oC, and none of the observed eruption responses rules out a sensitivity above 4.5oC.”

___________________________

Many more studies at http://tinyurl.com/6dqy2wc

19. Soundoff: “For example, all cars have had catalytic converters since 1975.”

No, some new cars had catalytic converters in 1975. There now over 200 million cars in the USA, and new car sales were around 14 million in the early 1990s.

How long would it take to get every car a CC?

However, Soundoff, I have offered references for my claim the great air cleanup of SO2 did not get started until 1990. Do you have any?

20. Mar 28th 2011

Sound,

Please read papers before citing them. Neither paper uses the eruption for a climate sensitivity measurement, they EXCLUDE it for calculating the sensitivity.

The basis for these papers is the ASSUMPTION that all warming is caused by CO2 forcing… Then they determine the sensitivity from that.

Don’t waste time citing unrelated articles.

21. Mar 28th 2011

Bruce,

Virtually all new cars sold in the USA had to have catalytic converters in place by 1975. Most cars on the road had them by 1985 and leaded fuel was eliminated by 1996 when almost no one was buying it anymore. These devices eliminated many pollutants including sulfur dioxide (SO2). The cleanup started long before that with automotive PCV systems in 1961, which were in full force by 1964. Emission standards were in place by 1968 and tightened annually thereafter. Catalytic converters were more of a replacement for the patchwork of devices already being used because they did not impact performance as much.

The acid rain cleanup mainly affected coal power plants, the last holdouts. They were more of a problem because they are concentrated sources of SO2 and NOx that have negative effects on downwind habitats, though health concerns played a role. The cleanup certainly did not start with acid rain legislation. Ended maybe.

Anyway I don’t want to debate history with you. Anyone look up this information by themselves. I’m interested in the science.

22. Mar 28th 2011

TIS,

I did read each of the 3 studies I referred you to. It’s not clear to me whether you did not understand them or you are attempting the same trick another famous (to me) skeptic uses. No matter how many refuting papers I pointed him to, he would claim they were about something else. Being right or wrong didn’t matter him, his goal was simply to provide disinformation to other readers (he is an executive in an oil exploration company so I understand his motivation). Even when I directly demonstrated he was wrong in my replies, he just diverted to some other subject or point. He would not deal with the argument made. He just cared about creating FUD. I hope that’s not you.

I forgot to include the link to the third study – it’s
http://www.climate-gate.org/cru/documents/volc.doc

The portion of the abstract I provided in my previous comment for that study clearly shows that it is about “Comparisons of observed and modeled coolings after the eruptions of Agung, El Chichon and Pinatubo [that] give implied climate sensitivities that are consistent with the IPCC range”. And there are 677 more articles in the list I gave you on the same subject if you don’t like that one.

Please give up this nonsense about climate sensitivity being some fraction a degree. You had some reasonable arguments to make in your other articles that I’ve read but not here. If climate sensitivity is some fraction a degree, climate would never change no matter what happened, and we know it has changed often, sometimes swiftly, and is changing now. I came here for a contrarian view of climate science but if foolish ideas are being proposed then it’s time for me to look elsewhere.

23. Mar 28th 2011

Sound,

Reading the abstract is different than sifting the article.

Article #1: Chris E. Forest
Page 3: The years 1963-4 and 1992 were removed to
limit the effect of the Mt. Agung and Mt. Pinatubo eruptions on the estimated temperature
changes.

Article #2: PIERS M. DE. FORSTER
Some fun quotes:
“If our results are accurate, it
could mean either that there is little or no positive wa-
ter vapor feedback and a neutral cloud feedback or it
could imply that the longwave cloud feedback is nega-
tive, offsetting the positive water vapor feedback”

The article does give an estimated sensitivity for Pinatubo (that is where they got the 1C for doubling, which is in my determined range), but they also say that:
“However, as our longwave results are
only well constrained for the 1985–90 period, it is prob-
ably premature to conclude that climate models are
incorrectly modeling longwave feedbacks.”

Hansen predicted in 1992 that Pinatubo would decrease temperatures 0.6C globally, but his personal GISS set only showed a third of that. Perhaps because his sensitivity is too high.

He could use satellite to get a higher sensitivity, but then he would get less warming. It is a conundrum.

I am not the only one getting less than 1C for a doubling of CO2. There are other peer reviewed articles that support my results…. Playing cite and article all day is boring and not research.

Sifting the numbers is the only way to see what is going on.

24. Very little SO2 comes from cars. Catalytic converters have nothing to do with SO2, and didn’t even work on nitrous oxides until the 3 way catalytic converter was introduced in 1981.

SO2 peaked in 1981.

http://www.pnl.gov/main/publications/external/technical_reports/PNNL-14537.pdf

25. Mar 28th 2011

Bruce,

You are correct that catalytic converters have nothing to do with SO2. Sulfur in gasoline is measured in the ppm magnitude.

Stratospheric SO2 is far more significant than tropospheric. This is why one of the bad ideas to stop global warming is to put SO2 into the stratosphere.
http://acd.ucar.edu/~dkin/Documents/2008JD011420.pdf

26. Mar 29th 2011

The definition of sulfur oxides (SOx) is “a general term for oxides of sulphur, which are emitted from motor vehicles burning fuel containing a high concentration of sulphur”.

Coal also has a lot of sulfur depending on the type used. If you want to have a long term effect on climate from a single event (like a volcanic eruption), then stick them in the stratosphere. Otherwise you need to keep dumping them into the lower atmosphere daily, which is exactly what we did prolifically from 1940 to 1970, when we started levelling off and then trending down.

From a government sulfur fact web site:

About 99% of the sulfur dioxide in air comes from human sources. The main source of sulfur dioxide in the air is industrial activity that processes materials that contain sulfur, e.g. the generation of electricity from coal, oil or gas that contains sulfur. Some mineral ores also contain sulfur, and sulfur dioxide is released when they are processed. In addition, industrial activities that burn fossil fuels containing sulfur can be important sources of sulfur dioxide.

Sulfur dioxide is also present in motor vehicle emissions, as the result of fuel combustion. In the past, motor vehicle exhaust was an important, but not the main, source of sulfur dioxide in air. However, this is no longer the case. [clearly something changed with respect to the motor vehicle component]

Steps taken to manage and reduce the amount of sulfur dioxide include:

Implementing national fuel quality standards
Supporting the implementation of tighter vehicle emission standards
Promoting alternative fuels
______________

“SO2 peaked in 1981”. Exactly my point. That’s long before acid rain cleanup was even started. Bruce’s link confirms the huge SO2 increase from 1940, the levelling off starting in 1970 and the peak in 1981, followed by a dramatic drop. The drop period coincides exactly with increased global warming. It also shows most of the post-1940 increase came from oil, which means transportation, which means vehicles.

27. Mar 29th 2011

I told you I read the articles not the abstracts. Now it’s clear to me that you did not understand what you read. One removes a period which has a specific effect to see what happens without the effect. The difference is the effect.

Note: This is my final comment on this web site. I’ve removed it from my reading list.

28. Mar 29th 2011

If you claim that a doubling of CO2 would lead to an increase in temperature of less than one degree, are then certain positive feedback mechanisms covered, such as an increase in methane from amongst others the thawing permafrost, or less albedo because of less snow and ice coverage? Such mechanisms would take a time to manifest themselves fully, which is of course not the case with the impact of more CO2 in the atmosphere, which is immediate. I don’t see how analysing the influence of volcanic eruptions can refute these claimed positive feedback mechanisms.

29. “Stratospheric SO2 is far more significant than tropospheric.”

Probably, but I’m more interested on the effect on weather stations, and the amounts we are discussing are not trivial.

1950-1980 Up 45 million tons to 75 million tons.

The radiative forcing change wrought by sulfate aerosols may be second only to that caused by carbon dioxide, albeit in the opposite direction (Shine et al. 1999; Ramaswamy et al 2001).
— PNL reference

“Global dimming is the gradual reduction in the amount of global direct irradiance at the Earth’s surface that was observed for several decades after the start of systematic measurements in the 1950s. The effect varies by location, but worldwide it has been estimated to be of the order of a 4% reduction over the three decades from 1960–1990.” Wikipedia

From 1980 to 2000 SO2 dropped 15 million tons.

‘…satellites confirmed measurements from ground stations show a considerable, and naturally-occurring, global brightening from 1983-2001 (Pinker et al., 2005). Elementary radiative-transfer calculations demonstrate that a natural surface global brightening amounting to ~1.9 Wm–2 over the 18-year period of study would be expected – using the IPCC’s own methodology – to have caused a transient warming of 1 K (1.8 F°). To put this naturally-occurring global brightening into perspective, the IPCC’s estimated total of all the anthropogenic influences on climate combined in the 256 years 1750-2005 is only 1.6 Wm–2.’ (Christopher Monckton)

And of course SO2 wasn’t the only pollutants increasing and decreasing in thoese time frames.

30. Mar 29th 2011

My personal view is based on net energy transfers, not flux or forcings. They are different.

Read the following to get my views on why sensitivity is low and feedbacks are not that critical.