A Rapid Reduction In Sulfur Aerosols Is Not Good for Climate Change

The increase in sulphur dioxide aerosols from the rapid expansion of coal burning in China and India, and shipping that utilizes high-sulphur bunker fuel in general, has created an increase in global dimming that has offset part of the global warming created by increases in greenhouse gases.

It now looks as if a significant amount of this offset may be removed within the next decade, accelerating global warming. The International Maritime Organization, which governs global shipping industry, passed regulations that will reduce sulphur emissions by 85% by 2020[i] [ii]. At the same time, China and India are working hard to reduce their sulphur emissions, to deal with very serious air pollution problems[iii] [iv].

Sulphur dioxide stays in the atmosphere for only a short amount of time, so a reduction in emissions will quickly lead to a reduction in atmospheric levels. Carbon dioxide stays in the atmosphere for many decades, or even centuries, so its warming effect will stay in place. The net effect will be to increase the global level of radiative forcing, as the dimming effect of the sulphur dioxide is quickly reduced.

With the global mean temperature having hit 1.260C above the pre-industrial in 2016[v], and not falling back as expected the the post El-Nino year of 2017[vi], there is little room left before the 1.50C limit is reached. A significant reduction in aerosols could add 0.10C or 0.20C in a short amount of time, concentrated in the areas of most pollution (e.g. China, India and shipping ports).


[i] Jan Fuglevstedt at. al. (2009), Shipping Emissions: From Cooling to Warming of Climates and Reducing Impacts on Health, Environmental Science & Technology. Accessible at http://pubs.acs.org/doi/pdf/10.1021/es901944r?cookieSet=1

[ii] Barbara Finamore (2016), Why the IMO’s 2020 Global Fuel Sulfur Limit Is Significant, NRDC. Accessible at https://www.nrdc.org/experts/barbara-finamore/why-imos-2020-global-fuel-sulfur-limit-significant

[iii] Ronal J. van der A et. al. (2016), Cleaning up the air: Effectiveness of air quality policy for SO2 and NOx emissions in China, Atmospheric Chemistry & Physics. Accessible at https://www.atmos-chem-phys-discuss.net/acp-2016-445/acp-2016-445.pdf

[iv] Rajesh Kumar Singh (2017), India will take at least 6 years to cap toxic emissions from power plants, The Economic Times. Accessible at http://economictimes.indiatimes.com/industry/energy/power/india-will-take-atleast-6-years-to-cap-toxic-emissions-from-power-plants/articleshow/59692402.cms 

[v] Hansen et. al. (2017), Global Temperatures in 2016, Columbia University. Accessible at http://www.columbia.edu/~jeh1/mailings/2017/20170118_Temperature2016.pdf

[vi] Scott Waldman (2017), Surprising Scientists, 2017 Could Be among Hottest on Record, Scientific American. Accessible at https://www.scientificamerican.com/article/surprising-scientists-2017-could-be-among-hottest-on-record/


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6 Responses to A Rapid Reduction In Sulfur Aerosols Is Not Good for Climate Change

  1. Joe says:

    Perhaps natural gas powered combustion turbines could add in hydrogen sulfide gas to the fuel stream at the point of use. There should be plenty of it available as it is normally removed from raw natural gas prior to feeding into pipelines. Gas power plants, which are displacing coal, could then to spew out lots of sulfur dioxide. As coal use declines the sky would be kept from clearing and acid rain would remain constant, rather than being reduced. Of course this strategy would require repeal of the Clean Air Act's current restrictions on sulfur in fuels.

    • rboyd says:

      There are a lot of different types of aerosol that scientists are looking at, given the shortcomings of sulphur aerosols. None seems to be perfect, best way to disperse seems to be at height in the atmosphere.

      We should be rapidly reducing GHG emissions, rather than start to rely on geo-engineering. That isn't happening of course, so probably by the 2030's we will be having real discussions about implementing these things.

      • Joe says:

        We should be rapidly reducing GHG emissions

        Agree totally, but I doubt that voluntary reduction will happen and also doubt that geo-engineering the climate will work either. I'm pinning my hopes on a fiscal crisis and subsequent collapse of the global market economy. Economic decline is the only proven method of reducing CO2 emissions (so far).

        • rboyd says:

          I see two options:
          1. Climate emergency with major countries imposing solutions by force (e.g. the UN Security Council) and some conflict. Still quite probability too little, too late - maybe in 2030's.

          2. Collapse will be too late AND will severely degrade the ability of nations to take action - 2040's - 2050's. If we get a quick drop in aerosols, then the temperature immediately jumps 0.5-1 degree centigrade. We will be well into feedback loops with the Earth taking the driving seat back from humanity.

          So ... 1) we are kind of screwed with some chance of some communities surviving at a level somewhat close to today 2) we are definitely screwed with modern society probably disappearing.

          Let's remember that we are already at 520ppm+ CO2e, and that's without an ice-free Arctic (the albedo change worth 100's of ppm CO2e in radiative forcing) and other feedbacks.

          If we use the GWP20 number for methane, an accurate representation of forcing over the next 20 years we are at 600+ ppm CO2e.

          • Joe says:

            What if collapse happens very soon and emissions go to near zero? Don't we end up at 1.5 C total warming?

          • rboyd says:

            A sudden removal in aerosols would definitely jump us through 1.5 degrees of warming, with much bigger localized jumps in the areas with the biggest pollution (e.g. China).


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