Are we cooling the planet with SO2?

Today I am going to ask a provocative question. Are we cooling the planet with Sulfur Dioxide (SO2)?

Cooling you might say? I thought we were warming? It could be that we are keeping the planet 4C cooler than it would have been (and still appear to be warming).

Sulfur dioxide “is the chemical compound with the formula SO2. It is a toxic gas with a pungent, irritating smell, that is released by volcanoes and in various industrial processes. ”

USGS: “The most significant climate impacts from volcanic injections into the stratosphere come from the conversion of sulfur dioxide to sulfuric acid, which condenses rapidly in the stratosphere to form fine sulfate aerosols. The aerosols increase the reflection of radiation from the Sun back into space, cooling the Earth’s lower atmosphere or troposphere. Several eruptions during the past century have caused a decline in the average temperature at the Earth’s surface of up to half a degree (Fahrenheit scale) for periods of one to three years. The climactic eruption of Mount Pinatubo on June 15, 1991, was one of the largest eruptions of the twentieth century and injected a 20-million ton (metric scale) sulfur dioxide cloud into the stratosphere at an altitude of more than 20 miles. ”

From 1850 to 1980 SO2 emissions rose from almost 0 to 140,000 Gigagrams per year in 1980 and then dropped down to 110,000 Gigagrams around 2000 and then it started to rise again as China began to burn a lot more coal.

Illustration from Atmos. Chem. Phys., 11, 1101–1116, 2011 pg 1107 Anthropogenic sulfur dioxide emissions: 1850–2005 S. J. Smith1, J. van Aardenne2,*, Z. Klimont3, R. J. Andres4, A. Volke1, and S. Delgado Arias1

Pinatubo released 20 million metric tons of SO2 into the atmosphere.

20 million metric tons = 20,000 Gigagrams.

Therefore, around 1980, humans were releasing the equivalent of 7 Pinatubo’s worth of SO2 each year into the atmosphere.

Seven Pinatubo’s per year!

Depending on which reference, the cooling of one Pinatubo = .5F or .5C or even .6C.

That would mean human produced SO2 should be cooling the earth by about 3.5C.

Yet temperature went up over .5C from 1980 to 2000.

Oh wait, SO2 went down from 1980 to 2000 the equivalent of one Pinatubo.

Could it be that if there was no human SO2 in the atmosphere the temperature recovery from the Little Ice Age could have been as high as 4C instead of the .8C claimed?

Maybe all that coal China is burning is saving our planet!

(Yes I know low level SO2 is supposedly not as bad as SO2 at 30,000 feet, but high altitude SO2 also causes some stratospheric warming – look it up)


  1. Funny you should mention 4 degrees C… I seem to recall reading somewhere, that the Earth’s temp fell about 4C, from the MWP into the depths of the LIA…. we’ve warmed .8C since 1850 (or if one wishes, the 2.5C since the past 250 years, or the heart of the LIA).
    They go into hysterics over this amount of rise, yet we still have 1.5C to go just to get back to the grand climate of the MWP? It makes no sense.


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