The Role of Sulfur Dioxide Aerosols in Climate Change

Guest essay by Buel Henry

In 2007, the Nobel Prize for Peace was awarded to Albert Gore and the IPCC for their work in promoting the theory that global warming was caused by green-house gasses, and that, based upon computer simulations, increasing amounts of these gasses in the atmosphere would cause runaway warming, with disastrous consequences for the planet.

At the time, this appeared to be a plausible explanation for the warming, since CO2 levels in the atmosphere were clearly rising. However, for the past 15 years or so, there has been a “Pause” (no statistically significant warming) in the warming trend, leaving scientists around the world scratching their heads for an explanation, since this was not predicted by any of their models.

However, it can be proven, from published data, that the observed warming was actually a “side effect” of the American Clean Air Acts (1963, 1979, 1990 ) and similar efforts abroad, and had nothing to do with greenhouse gasses..

Just as the global cooling caused by a large volcanic eruption ends after its stratospheric Sulfur Dioxide  (SO2) aerosols have settled out of the atmosphere, warming will naturally occur when anthropogenic SO2 aerosols are likewise removed from the troposphere.

As the Clean Air Act efforts were implemented, warming naturally occurred, as it was expected to, but the warming was wrongly attributed to greenhouse gas emissions rather than simply to the cleaner, more transparent air (fewer dimming SO2 aerosols to weaken the sun’s rays). The eruptions of Mt. Pinatubo and Mount Hudson (1991) injected 23 million tonnes of SO2 into the stratosphere, according to TOMS satellite measurements (plus other fine particulates which settled out within a few weeks), leaving a cloud of sulfate aerosols that circled the globe and persisted for about 2 years before finally settling out. Examination of the Goddard Institute for Space Studies (GISS) monthly temperature maps shows that global cooling, from the pre-eruption level, reached 0.45 deg. C. in November of 1992.

As the pollution settled out, temperatures rose to pre-eruption levels, because of decreased dimming, an increase of 0.45 deg. C. from the nadir.This represents a temperature rise of approx. .020 deg. C. for each Megatonne of SO2 removed.

Anthropogenic emissions of SO2 into the troposphere peaked during year 1972 at about 131 Megatonnes. By year 2000, due to worldwide Clean Air Act efforts, SO2 emissions in the West had decreased by approximately 48 Megatonnes. However, during the same time period, emissions elsewhere rose by 23 Megatonnes, for a net worldwide decrease of 25 Megatonnes.

According to the NASA fact sheet on atmospheric aerosols, both stratospheric (volcanic) and tropospheric aerosols have the same climatic effect:

“Strato-spheric SO2 aerosols reflect sunlight, reducing the amount of energy reaching the lower atmosphere and the Earth’s surface, cooling them”. Human-made sulfate aerosols “absorb no sunlight but they reflect it, thereby reducing the amount of sunlight reaching the Earth’s surface”.

The changing levels of SO2 emissions around the world are nicely shown in the graph “Global Anthropogenic SO2 Emissions” in the paper “Anthropogenic Sulfur Dioxide Emissions:1850-2005” by S. J. Smith, et al. The graph was compiled from published data by Robert A. Rhode. The 1972-1985 SO2 emission levels cited herein were extracted from that graph, and emissions from 1990-2011 were taken from “The last decade of global anthropogenic sulfur dioxide: 2000-2011 emissions”, Table S-1, by Z. Klimont, et al.

Applying the “.020 deg. C. per Megatonne of SO2 removed” relationship to the net 25 Megatons of SO2 removed, 1972-2000, due to global Clean Air efforts, an average global temperature rise of 0.50 deg. C. would be expected. The NASA Global Land-Ocean Temperature Index GHCN-v3, shows a rise of 0.38 deg. C., (0.12 Deg. C. lower). However, this lower temperature rise was due to the effects of the strong 1998-2001 La Nina which depressed average global temperatures.

Otherwise, both temperatures would have been nearly identical.

In contrast, the models incorporating CO2 in the IPCC fourth assessment report (Figure SPM 5) projected an increase of 0.8-1.2 deg. C. for the same time period, much too high.

With respect to anthropogenic SO2 emissions from intermittent sources, they will generally settle out of the atmosphere within a few days. The conversion of SO2 to Sulfuric Acid (the SO2 aerosol) happens very quickly, so it acts as a dimming aerosol even in that short time.

However, the bulk of anthropogenic SO2 emissions come from relatively constant sources such as power plants, factories, foundries, vehicle exhausts, home heating units, maritime shipping, and the like. The atmosphere is never free of their dimming aerosols since they are constantly being renewed. As such,.they have a much longer effective lifetime than aerosols injected into the stratosphere, ending only when the emitting sources are either modified to reduce emissions, or are shut down.

The fact that an empirically-derived factor from the Mount Pinatubo eruption can be used to accurately predict the amount of temperature rise resulting from the removal of 25 Megatons of dimming anthropogenic SO2 aerosols due to Clean Air Act efforts is further proof that the climatic behavior of stratospheric and tropospheric SO2 aerosols is identical.

It also proves that the IPCC “Graph of Radiative Forcings” is completely incorrect, since it does not include any warming due to the removal of dimming-aerosols from the atmosphere. To be correct, this forcing needs to be included (which will have the effect of completely eliminating any forcing due to CO2). As noted above, all of the warming can be accounted for by the reduction in SO2 emissions.

The ultimate test of any hypothesis lies in its predictive ability. Above, it accurately predicted the amount of warming that would occur when a net of 25 Megatonnes of SO2 emissions were removed from the atmosphere.

Another example (using data from the Table S-1 cited above): Between 2000 and 2005, anthropogenic SO2 emissions increased by 5.58 Megatonnes, thus decreasing the 25 Megatonnes of reduction by that amount, lowering it to 19.4 Megatonnes. This was followed by a reduction in anthropogenic SO2 emissions between 2005 and 2010 of 9.28 Megatonnes, giving a final net reduction of 28.7 Megatonnes at 2010, for an expected anomalous temperature rise, 1972-2010, of .020 x 28.7 = .0.57 deg. C., versus a NASA’s 2010 value of 0.66 deg. C. (GISS value of 0.61 deg. C) (It should be noted that NASA and

GISS values were essentially identical until about 2005, but NASA values have trended higher since then).

The slightly higher-than-predicted temperature rise was due to the moderate 2009-2010 El Nino, which, in this case, temporarily raised global temperatures Without the El Nino warming, the actual and predicted temperatures would would have been essentially identical.

This can be seen on the accompanying annotated graph of global temps. 1972-2011. The graph shows the “background” warming due to the removal of SO2 aerosols, and deviations above and below that line due to natural causes, such as El Niños, La Niñas, volcanic eruptions and (probably) non-eruptive SO2 ventings, such as currently coming from Baroarbunga, in Iceland.

The graph also shows that the “pause” is caused by the near balance in the amounts of global increases and decreases of SO2 emissions since 2001.

This balance, however, cannot be expected to continue, because of planned EPA actions, and efforts to reduce pollution in the Far East.

During the 1930’s depression era, global anthropogenic SO2 levels decreased, largely due to reduced industrial activity Between 1930 and 1938, for example, they fell by approx. 29 Megatonnes (see the graph of Global Anthropogenic SO2 emissions cited above) Again, using the “.020 deg. C.” factor, an average global temperature rise of 0.58 deg. C. would be expected, NASA and GISS temp. values show a rise of only 0.30 deg. C, for that period, but, again, a strong La Nina (8th strongest in 115 years) in 1938 lowered the average global temperature. Without it, both values would have been much closer.

The accuracy of the above three examples proves that the “.020 deg.C.temp. rise for each Megatonne of SO2 removed” relationship is basically correct (although some minor adjustment may need to be made as it is more closely examined). Conversely, an increase in the amount of SO2 in the atmosphere should cause a decrease in global temperatures.

This happened, for example, in the 1960 -1972 period, when global levels of SO2 emissions rose from 93 Megatons to 131 Megatons, an increase of 38 Megatons. This was the period when there were concerns that a new Ice Age might be dawning, because of the lower temperatures being experienced.

The phenomenon of global brightening, as detected by satellites, also mirrors the reduction in SO2 levels in the atmosphere, as would be expected. According to the Wikipedia article on Global Dimming the switch from a “global dimming” trend to a “global brightening” trend began around 1985, just as global SO2 emissions started to significently decline, and basically ended when the “pause” began, in 2000.

Twenty-one of the 25 Megatonnes (84%) of net SO2 emission decreases, 1972-2000.were removed in the 1985-2000 period of global brightening, as well as 84% of the resultant temperature rise, 1972-2000. The “brightening” in the absence of any increased solar output, could only have been caused by ewer dimming aerosols, resulting in increased warming of the earth’s surface.

Of the 131 Megatonnes of SO2 emissions present in the troposphere in 1972, a net global reduction of only about 29 Megatonnes occurred by 2010. This was sufficient to raise average global temperatures by about 0.60 deg. C, and is the primary cause of the California drought.

It is unfortunate, but further actions to reduce SO2 emissions, especially by the EPA, and in Eastern Asia, can be expected to cause ever-increasing temperatures.

Since CO2 has been shown to have no climatic effect, all efforts to reduce CO2 emissions in hopes of controlling global warming will be a waste of resources.

As the climatologist Beate Liepert remarked in 2005:

“We thought we lived in a global warming world, but this is actually not right. We live in a global warming plus a global dimming world, and now we are taking out the global dimming. So we end up with a global warming world, which will be much worse than we thought, much hotter”.

References:

Clean Air Acts: http://www2.epa.gov/laws-regulations/summary-clean-air-act

NASA fact sheet on atmospheric aerosols: http://www.nasa.gov/centers/langley/news/factsheets/Aerosols.html

“Anthropogenic Sulfur Dioxide Emissions:1850-2005″ by S. J. Smith http://www.atmos-chem-phys.net/11/1101/2011/acp-11-1101-2011.pdf

The last decade of global anthropogenic sulfur dioxide: 2000-2011 emissions”, Table S-1, by Z. Klimont, et al. http://iopscience.iop.org/1748-9326/8/1/014003

IPCC fourth assessment report (Figure SPM 5) https://www.ipcc.ch/publications_and_data/ar4/syr/en/figure-spm-5.html

NASA GISS global surface temperature: http://data.giss.nasa.gov/gistemp/