Killer Air: Comparing models and data

As the AP  reports  Lelieveld has published a paper in Nature  on the mortality associated with outdoor air pollution that  confirms what BerkeleyEarth found in its study of air pollution in China. By their estimate   ~1.357M deaths in China are caused by air pollution. By our estimate there are ~1.6 Million deaths per year in China due to air pollution, or roughly 18% more than Lelieveld’s computer modelling estimates.  When we consider the uncertainties involved in both estimates,  the conclusion is essentially the same: Air pollution kills, and not only in China, but around the world. By their estimate worldwide deaths top 3 million per year.


As Richard Muller writes:

“The pieces are all fitting together; the picture is emerging from the jigsaw puzzle.  The case is getting stronger that air pollution around the world is a severe, perhaps the most severe environmental disaster in the world today.  Someday it might be overtaken by global warming, but air pollution is today’s killer. Worldwide, PM2.5 kills more people per year than AIDS, malaria, diabetes or tuberculosis, and its effects are most damaging in the developing world. But even in the US, air pollution is responsible every year for more deaths than those caused by automobile accidents.”


The Lelieveld work provides an important complement to our study. Both studies used the same WHO approach to estimating mortality from PM2.5 concentrations; however, the two papers took different approaches to estimating   concentrations. BerkeleyEarth worked from ground station data: air quality measurements taken at ground level at over 900 locations in China. We recorded the actual concentration levels in situ. The Lelieveld study took a different approach.


Working from the Emissions Database for Global Atmospheric Research (EDGAR) which estimates source emissions and combining that with a weather and chemical transport model, Lelieveld et al, were able to estimate concentrations globally. This approach has uncertainties since the data relies on estimates of emissions and their sources, not to mention the uncertainties involved in estimating transport. Nevertheless, the estimates they obtained for mortality match with our estimates for mortality. Since the results match in areas where we have actual observations of PM2.5 concentrations we have some measure of confidence in their global numbers


On benefit of the modelling approach  is that it allows you to make estimates in areas where you have no air quality measurement systems. As BerkeleyEarth continues to expand it collection of obsveration from Japan,India, Europe and other parts of the world, we will be in a position to report on the accuracy of the modelling in those parts of the world


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