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Tue Mar 22, 2016, 08:55 PM

Nature: The Planet May Be In Trouble If China Controls It's Air Pollution. [View all]

Recently, in this space I referred to a paper published in Nature, (Nature 525, 367–371 (17 September 2015)) that reports that air pollution in China kills 1.4 million people per year.

My remarks are here: Nature: China's annual air pollution deaths now stand at 1.4 million per year

An excerpt from the original paper is now included:

Considering the global population of 6.8 billion in 2010, it follows that the mean per capita mortality attributable to air pollution is about 5 per 10,000 person-years. Of these 5 persons per 10,000 worldwide, about 2 die by CEV, 1.6 by IHD, 0.8 by COPD, 0.35 by ALRI and 0.25 by LC. The highest per capita mortality is found in the Western Pacific region, followed by the Eastern Mediterranean and Southeast Asia. The combination of high per capita mortality with high population density explains the (by far) highest number of deaths in the Western Pacific, China being the main contributor (1.36 million per year). Note that the mortality attributable to air pollution in China is approximately an order of magnitude higher than that attributable to Chinese road transport injuries and HIV/AIDS, and ranks among the top causes of death28. Southeast Asia has the second highest premature mortality, where India is the main contributor (0.65 million per year). The global mortality linked to air pollution is strongly influenced by these high numbers in Asia.

Even I rounded up, by 40,000 human lives, it still seems dire, no? (Who's counting? It's not like plus or minus 40,000 human lives count, unless the deaths can be attributed somehow to nuclear power, like say, Fukushima.)

This week's Nature raises a new worry about Chinese air pollution: That China may get air pollution under control.

First from the "news item" referring readers to the technical article within the journal:

Nature 531, 310–312 (17 March 2016)

In December 2015, world leaders agreed to limit the increase in global average temperature to less than 2 °C above pre-industrial temperatures (see Nature 528, 315–316; 2015). Meeting this aspiration will require large and rapid reductions in greenhouse-gas emissions, making it imperative to understand and account for the emissions from different countries. China has undergone rapid economic development over the past few decades and now has one of the world's largest economies — and greenhouse-gas emissions to match. On page 357 of this issue, Li et al.1 comprehensively assess China's contribution to climate change and explore how this has altered as the Chinese economy has grown...

...Li et al. used a model that couples biogeochemistry and climate to estimate China's contribution to global radiative forcing over the period 1980–2010. Crucially, they account for almost all anthropogenic drivers of climate change. They find that China's relative contribution to global radiative forcing from carbon dioxide emissions associated with fossil-fuel use increased almost threefold in these 30 years. This is to be expected, given the surge in China's economy over this period. More surprisingly, they find that China's relative contribution to total global radiative forcing has remained at 10% over this time.

To understand the reasons behind this remarkable result, Li and colleagues made a detailed analysis of the different drivers of radiative forcing. They found that the air pollutants that cause China's notorious pollution haze have had complex effects on climate, counteracting some of the increase in radiative forcing from greenhouse gases. Some components of air pollution, such as black-carbon particles, absorb sunlight and warm Earth's climate. By contrast, sulfate particles scatter light, resulting in climate cooling.

Over the past few decades, China's relative contribution to global radiative forcing from sulfate has increased dramatically. This is because Chinese sulfate emissions soared at the same time that Europe and the United States instigated controls that slashed their sulfate emissions. It has long been known that some air pollutants cool the climate2; what is remarkable in the present study is that the concurrent changes in different emissions have led to a stable overall contribution of China to global radiative forcing (Fig. 1).

Here is the technical paper: The contribution of China’s emissions to global climate forcing (Nature 531, 357–361 (17 March 2016))

From the text of the technical paper:

Figure 1 shows the relative and absolute contributions of historical Chinese emissions since 1750 to each component of global RF in 2010. Overall, China contributes 10% ± 4% (0.30 ± 0.11 W m−2 out of 2.88 ± 0.46 W m−2) of the current net global RF from anthropogenic emissions since 1750. This contribution is the sum of two terms with opposite signs. China contributes 12% ± 2% (0.48 ± 0.09 W m−2 out of 4.13 ± 0.40 W m−2) of the global positive RF from WMGHGs, tropospheric ozone and black carbon aerosols, and 15% ± 6% (−0.18 ± 0.06 out of −1.26 ± 0.24 W m−2) of the global negative RF from LUC-induced surface albedo changes, stratospheric ozone, the effect of ozone precursors on CH4 lifetime, and sulfate, nitrate and particulate organic matter aerosols.

Abbreviations: RF = Radiative forcing. WMGHG = Well Mixed Green House Gases LUC = Land Use Changes

According to the authors, the past counts, in case people want to argue that it's all China's fault, even though China's per capita emissions are about 1/4 that of Americans:

...It is important to note that the contribution of China to current global annual anthropogenic emissions is larger than its contribution to radiative forcings (Fig. 1). For WMGHGs that have long atmospheric lifetimes7 (from a few decades to several centuries), the legacy of past emissions from countries that began to emit early (such as Europe and the USA) still have a contribution to present-day RF larger than that of China, despite China’s much higher emissions nowadays. In contrast, because SLCFs have short atmospheric lifetimes7 (from days to months), it is the spatial distribution of current emissions, and the local processes controlling their atmospheric transport and removal, that determine the contribution of Chinese emissions of ozone precursors and aerosols to the global RF...

Of course, you had nothing to do with it at all, because you have a solar powered electric car made by BMW or Tesla or some other wonderful company that works on your brain like a narcotic at best, a hallucinogen at worst.


Some graphics from the paper:

a, The global RF components and their uncertainty, as estimated by the IPCC7. b, The relative contributions of China to the various components of global RF in 2010, with our assessment of uncertainties (see Methods). When one component of the RF is driven by only one species, China’s relative contribution to present-day emissions of that species is also shown as an empty bar oulined in the same colour. c, The absolute contributions of China to the RF components and uncertainties, as obtained by combining the values of the two previous panels using a Monte Carlo approach (n = 50,000). The ‘Total’ columns of a and c are obtained through Monte Carlo summation (n = 50,000) of the corresponding RF components; the ‘Total’ column of b is then deduced through the element-wise ratio of these two Monte Carlo ensembles. All uncertainties are one standard deviation.


All-sky RF of the SLCFs induced by China through emission of short-lived pollutants and precursors in 2010. These RFs are direct outputs from the LMDz-INCA model. a, The net RF of all the SLCFs combined. b–f, The RFs from black carbon, sulfates, tropospheric ozone, nitrate and particulate organic matter, respectively.

Returning to the news item:

Air pollution is a serious environmental issue in China, where 1.3 million people die each year because of exposure to poor-quality air outdoors3. Reductions in the emissions of air pollutants are urgently required to improve air quality, but this will also affect Earth's climate. Li et al. find that the current composition of Chinese air pollution causes almost no net radiative forcing — the cooling effects of sulfate aerosols balance the warming impacts of black-carbon emissions.

(The round down by 60,000 human deaths, but who's counting? It's not like Fukushima is involved.)

If you think it's hot now, just wait. China's rapid coal growth has stopped, and, as a result, it's sulfate loads are no longer rising as fast. Like many other rich countries, they're burning more and more dangerous natural gas. (They also have the world's largest program of building nuclear reactors.)

Don't worry. Be happy. France is building a solar roadway. It's meaningless, but it's the thought that counts.

Have a nice day tomorrow.

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