On Friday, March 6 2009, Professor Gregory R. Carmichael of the Department of Chemical & Biochemical Engineering at The University of Iowa presented one the most insightful talks I have ever attended. The title of this talk was “What Goes Around Comes Around”.
There were several very important findings that were presented, which include
1. “We know that regional control strategies are needed to meet local air quality targets”. [from slide 4]
This perspective recognizes that it is regional weather and climate that needs to be focused on in order to improve air quality.
2. with respect to air pollution ” Large and small sources combine resulting in a global reach of pollution…..The majority of impacts are domestic, BUT Intercontinental transport of PM2.5 is associated with 100,000 premature mortalities world-wide of adults 30 years and older. Intercontinental transport of PM2.5 into USA results in ~1200 excess deaths! (tightening the U.S. 8-hour O3 standard from 84ppbv to 75ppbv, is annually projected to prevent 1,300 to 3,500 premature deaths in the United States at a cost of $7.6-8.8 billion USD each year [EPA, NAAQS RIA, 2008]) [from slide 11]”.
The global reach of pollution that Professor Carmicheal finds is in agreement with one of the findings in the 2005 NRC report that
“Regional variations in radiative forcing may have important regional and global climatic implications that are not resolved by the concept of global mean radiative forcing. Tropospheric aerosols and landscape changes have particularly heterogeneous forcings.”
3. “As air quality standards become more stringent the importance of distant sources increases. [The] contribution of Asia pollution to [the] USA is growing — we estimate that it is nullifying 15% of our emission reduction efforts !!”
This conclusion also supports the 2005 NRC conclusion that is presented under #2.
4. “Full application of advanced emission control technologies can reduce health impacts in China by 43% in 2030; optimized saves 80% of costs”.
Professor Carmichael showed that this benefit also results in an 8% decrease in greenhouse gas emissions even with a focus on air quality benefits
This conclusion shows that by focusing on improving air quality can also result in a reduction of greenhouse gases. However, as shown in #5, delaying the reduction of certain types of aerosols (e.g. sulphates) in order to retain a global average radiative cooling will result in early deaths than otherwise would not occur.
5. “350,000 excess deaths per year in India and China due to outdoor exposure risk for each 20mg/m3 (of fine aerosols of less than 2,5 microns). In addition to a WHO estimate of 381,000 and 407,000 (deaths) for China and India, respectively, from indoor air pollution caused by solid fuel use.”
This conclusion documents the immediate benefit of reducing fine particles in the atmosphere regardless of the impact on the emissions of greenhouse gases.
The only part of his talk which I disagreed with was his conclusion to decrease black carbon emissions faster than sulfates [from slide 19]. As Professor Carmichael reports in #4, excess deaths can be reduced if fewer fine particles are emitted into the atmosphere that is breathed. It does not matter if these are sulphates or black carbon (or other aerosols). A delay in reducing sulphates simply to retain their globally cooling effect would condemn many people to an early death.