[Charlie]

Charlie asked the Naked Scientists:

I recently heard a short story about a possible fix to global warming. 

It entails putting sulphur into the atmosphere, much less than what is  currently emitted into the atmosphere.  This is supposed to cool the earth. How?

Thanks!


What do you think?

[hlr]

Very small airborne particles and droplets (called aerosols) are released into the atmosphere from both natural (e.g. dust storms, volcanoes) and manmade (e.g. fossil fuel and biomass burning) sources. One such type of particle is called 'sulphate aerosol' which contains sulphur in the form of sulphuric acid.

Aerosols are known to significantly influence the radiative budget of the Earth's atmosphere. These aerosols act in two distinct ways: (1) directly, by scattering and absorbing radiation from both the Sun and Earth's surface; and (2) indirectly, by changing the radiative properties and amount of clouds.

Aerosols in the atmosphere are removed largely and relatively rapidly by rainfall (usually within a week) and therefore remain close to their source region.  The impact of aerosols on global warming depends on the location of the aerosols as well as their size, shape and composition.  As a result of these factors it is difficult to calculate the climate effect of aerosols.

The latest scientific thinking however is that the direct effect of sulphate aerosols present in the atmosphere may cool the climate by approximately -0.2 W/m2 (n.b. the climate response due to carbon dioxide is currently calculated to be +1.46 W/m2). IPCC, 'Climate Change 2001'.

It should also be noted that emissions of sulphur also contribute significantly to local air quality (e.g. The Great London Smog, December 1952) and even moderate concentrations may result in a fall in lung function in asthmatics.

You asked whether putting sulphur into the atmosphere may be a 'possible fix to global warming'...in response, I would say that large amounts of sulphate aerosol in the atmosphere would act to cool the climate.  But how much we would need, and what the impact on local air quality and the other atmospheric gases would be is debatable! We may make things a lot worse!

[frethack]

Ahhhh....acid rain.  Trees love that stuff.

[chris]

Thanks Helen, brilliant answer.

And, incidentally, Helen (who answered the question above) has just published an article on the Naked Scientists about aviation, shipping and global warming. Here's the URL:

http://www.thenakedscientists.com/HTML/articles/article/uplifting-insights-into-aviation-and-climate/

Chris