Environment

Jun 6, 2011

Global warming above 2° so far mitigated by accidental geo-engineering

According to NASA’s Goddard Institute of Space Science climate reports, global warming is already committed to a rise above two degrees, writes Dr Andrew Glikson, Earth and paleoclimate science, Australian National University

According to NASA’s Goddard Institute of Space Science climate reports, global warming is already committed to a rise above two degrees. The magical two degrees ceiling determined by governments is only holding thanks to effective, if unintended, geo-engineering by sulphur dioxide emitted from industry, holding global warming to about half of what it would be otherwise. Recent publications by Hansen and his research group indicate the rise of atmospheric energy (heat) level due to greenhouse gases and land clearing are committed to +2.3 degrees (+3.1 Watt/m2), currently mitigated by the transient effect of sulphur aerosols and the cooling effect of the oceans. Sulphur dioxide is emanated from coal, oil and the processing of minerals (breakdown of sulphides to produce copper, zinc, lead and so on), and from other chemical industries. It combines with water in the atmosphere to produce sulphuric acid, which (being heavier than air) condenses and settles to the ground within a few years. Aerosols stay in the atmosphere and stratosphere on time scales ranging from hours to days and to years, depending on their grain size, chemistry and height in the atmosphere and on the physical state and temperature of the atmosphere at different altitudes and latitudes. The aerosols are short-lived, i.e. on time scales of up to a few years, but since they are continuously emitted from industry the overall level is increasing as burning of fossil fuels is rising. The continuing emission of sulphur aerosols in effect constitute a global geo-engineering process without which the atmosphere would warm by another 1.2 degrees (1.6 Watt/m2) above the present level, resulting in near-doubling of global warming (Figure 1):

Had it not been for the cooling effect of the short-lived (a few years long) sulphur aerosols, the internationally agreed maximum temperature ceiling of two degrees would have been transcended. Cleaning of aerosol emissions, required in some countries, would result in thinning of the aerosol shield and thereby further warming. At present measured temperature rise since 1880 of approximately +0.8 degrees is lagging behind +1.1 degrees warming (mitigated by sulphur aerosols), mainly due to the buffering effect of the oceans. The temperature rise lag period is not known but has been estimated as 35 years. Whereas according to the IPCC AR4 (2007) mean global land/ocean temperature since 1880 has risen by about +0.8C, this translates to more than +4C rise in the polar region of northern Canada, Greenland and Siberia (Figure 2).

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6 comments

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6 thoughts on “Global warming above 2° so far mitigated by accidental geo-engineering

  1. John Bennetts

    Where’s Tamas Calderwood and his attempts at rebuttal of Andrew Glickson’s facts?

  2. stephen martin

    Why the different bases to indicate the warming – surely the data should be compared to the long term trend.
    I find it noteworthy that the November 2010 data shows cooling over much of eastern Australia, you would have expected warming surely with the onset of one of the strongest el Nina events ever recorded.

  3. stephen martin

    Sorry, that of course should read one of the strongest la Nina events.

  4. Mark M

    @Stephen Martin

    Sorry, that of course should read one of the strongest la Nina events.

    La Nina causes rains on the East coast of Australia. Not sure where you get the warming idea from – La Nina is generally associated with cooler global temperatures – as we have seen in Australia in late 2010, early 2011.

  5. stephen martin

    @ Mark M

    I am aware of course aware of the related rain in eastern Australia as a result of a la Nina event. The point is that the waters of the south American coast are a lot colder than normal (and warmer than normal with an el Nino event.) the colder waters are balanced by increased convection over east Australia caused by warm than normal air masses. That was my point above.

  6. Boerwar

    I used to yearn for access to good science writing about AGW.

    Now that we get it at Crikey, I am reminded of one of my aunties, a migrant, who refused to learn english in case she ended up reading newspapers.

    She reckoned she was happier not knowing things.

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