“MOST people are under the impression global warming has risen by about 0.8 degrees C since the dawn of the industrial age. Unfortunately, mean temperatures have risen much further when account is taken of the short-term masking effect of aerosols emitted from coal and oil, mainly sulphur dioxide and its oxidized products…
“Thus, according to the IPCC AR4-2007 report (figure SPM.2), the total anthropogenic greenhouse effect since 1750 AD, which is equivalent to about +2.3 degrees C, is masked by a compensating aerosol albedo effect equivalent to about -1.1 degrees C. However, given the short-lived residence time of sulphur aerosols in the atmosphere, this masking effect dissipates within periods up to a few years.
“Currently continuing emission of SO2 maintains the aerosol albedo effect, preventing further sharp temperature rises. But in a situation akin to methadone addiction, proposed reduction of sulphur emissions would lift this barrier, enhancing global warming.
“A dissipation of aerosols and the melting of polar ice would raise polar temperature anomalies to levels exceeding even the current 4 to 5 degrees C warming in parts of the Arctic circle, Siberia and west Antarctica.”
That’s according to Andrew Glikson, a visiting fellow at the Australian National University, writing for www.crikey.com.au last week.
I’m wondering whether Dr Glikson has a point when it comes to aerosols – they are so prevalent in the skies of south-east Asia. Is the -1.1 degrees C a reasonable guestimate for their impact globally?
Notes and Links
Global warming toward the EU’s upper limit, MONDAY 1 JUN 2009, by
paleoclimate scientist Andrew Glikson, http://www.crikey.com.au/2009/06/01/global-warming-toward-the-eus-upper-limit/
Dr Glikson’s home page: http://ems.anu.edu.au/people/glikson/
Hong Kong harbour in a mist of smog; the photograph was taken in September 2006 by Jennifer Marohasy.