Tuesday, July 19, 2011

New paper says volcanoes, not Chinese coal emissions, are mainly responsible for no global warming

Remember the paper two weeks ago confidently claiming the reason why global warming stopped in 1998 was due to an increase in man-made sulfur emissions from Chinese coal burning? Well, this week it's mainly due to natural sulfur emissions from volcanoes.

Key Points
  • Minor tropical volcanic eruptions: important source of stratospheric aerosols
  • Stratospheric aerosol layer mainly impacted by those events
  • Potential impacts on climate and ozone chemistry
J.-P. Vernier et al

The variability of stratospheric aerosol loading between 1985 and 2010 is explored with measurements from SAGE II, CALIPSO, GOMOS/ENVISAT, and OSIRIS/Odin space-based instruments. We find that, following the 1991 eruption of Mount Pinatubo, stratospheric aerosol levels increased by as much as two orders of magnitude and only reached “background levels” between 1998 and 2002. From 2002 onwards, a systematic increase has been reported by a number of investigators. Recently, the trend, based on ground-based lidar measurements, has been tentatively attributed to an increase of SO2 entering the stratosphere associated with coal burning in Southeast Asia. However, we demonstrate with these satellite measurements that the observed trend is mainly driven by a series of moderate but increasingly intense volcanic eruptions primarily at tropical latitudes. These events injected sulfur directly to altitudes between 18 and 20 km. The resulting aerosol particles are slowly lofted into the middle stratosphere by the Brewer-Dobson circulation and are eventually transported to higher latitudes.

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