ScienceDaily (July 6, 2012) — Atmospheric scientists at the Harvard School of Engineering and Applied Sciences (SEAS) and Nanjing University have produced the first "bottom-up" estimates of China's carbon dioxide (CO[SUB]2[/SUB]) emissions, for 2005 to 2009, and the first statistically rigorous estimates of the uncertainties surrounding China's CO[SUB]2[/SUB] emissions.
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The independent estimates, rooted in part in measurements of pollutants both at the sources and in the air, may be the most accurate totals to date. The resulting figures offer an unbiased basis on which China might measure its progress toward its well-publicized CO[SUB]2[/SUB] control goals.
The findings were published July 4 in the journal Atmospheric Environment.
"China's emissions of CO[SUB]2[/SUB] are of central concern in efforts to combat global climate change," says lead author Yu Zhao, a former postdoctoral researcher at Harvard SEAS who is now a professor at the Nanjing University School of Environment in China. "But despite all of the attention to China's CO[SUB]2[/SUB] emissions, they're less well quantified than most people realize."
Existing estimates for these emissions are calculated "top-down," based on annual energy statistics that are released by the Chinese government. The nation has only once officially estimated its CO[SUB]2[/SUB] emissions, based on national energy statistics from 1994, although it is now constructing a data system to produce periodic national greenhouse gas inventories. Non-Chinese organizations, such as the U.S. Department of Energy and the Netherlands Environment Agency, produce widely cited CO[SUB]2[/SUB] estimates for China (among other countries), but these are also based on the national energy data.
A study published last month by a China-U.K.-U.S. team in Nature Climate Change spotlighted a large disparity in estimates of Chinese CO[SUB]2[/SUB] emissions when the numbers were based on national energy statistics versus summed provincial data. To illustrate the contrast, those researchers had applied a standardized U.N. protocol for estimating the emissions of any developing country by sector.
The new Harvard-Nanjing study goes deeper, however, constructing a "bottom-up" emission inventory that is specific to China's energy and technology mix. It combines the results of Chinese field studies of CO[SUB]2[/SUB] emissions from diverse combustion processes with a plant-by-plant data set for power generation, independent research on transportation and rural biomass use, and provincial-level energy statistics for the remaining sectors.
The Harvard-Nanjing team believes provincial energy data to be more accurate than national statistics because the provincial data have been empirically tested in peer-reviewed atmospheric studies that compare the expected emissions of conventional air pollutants to actual instrumental observations by satellites and ground stations. Provincial statistics also take into account the large quantities of coal produced by small, illegal mines.
"There are several different ways to estimate emissions of greenhouse gases or air pollutants, from those designed to support policy processes to those made by scientists researching atmospheric transport and chemistry," explains co-author Chris Nielsen, Executive Director of the Harvard China Project, which is based at SEAS.
The former methods suit the needs of policy, attributing emissions to identifiable sources for actionable controls, but the latter are often more environmentally accurate, according to Nielsen.
"The methods used by atmospheric scientists can be more complete, incorporating new research on dispersed sources that are poorly represented in official statistics or weakly targeted by policy -- such as the burning of crop wastes in fields or biofuels in poor, rural homes," Nielsen explains. "The data are also more detailed in spatial terms. This allows a comparison of emission estimates to the pollution levels measured at the surface, or from space, testing the underlying energy data in the process."
The new study capitalizes on prior tests and a bottom-up data framework that has been demonstrated for conventional air pollutants to produce a more thorough estimate of China's CO[SUB]2[/SUB] emissions.
The new study also quantifies the uncertainty of the emission totals, applying formal statistical methods. For instance, the team found that the 95% confidence interval for the 2005 CO[SUB]2[/SUB] estimate lies between
See Also:
- Consensus of scientists regarding global warming
- Fossil fuel
- Automobile emissions control
- Scientific opinion on climate change
The independent estimates, rooted in part in measurements of pollutants both at the sources and in the air, may be the most accurate totals to date. The resulting figures offer an unbiased basis on which China might measure its progress toward its well-publicized CO[SUB]2[/SUB] control goals.
The findings were published July 4 in the journal Atmospheric Environment.
"China's emissions of CO[SUB]2[/SUB] are of central concern in efforts to combat global climate change," says lead author Yu Zhao, a former postdoctoral researcher at Harvard SEAS who is now a professor at the Nanjing University School of Environment in China. "But despite all of the attention to China's CO[SUB]2[/SUB] emissions, they're less well quantified than most people realize."
Existing estimates for these emissions are calculated "top-down," based on annual energy statistics that are released by the Chinese government. The nation has only once officially estimated its CO[SUB]2[/SUB] emissions, based on national energy statistics from 1994, although it is now constructing a data system to produce periodic national greenhouse gas inventories. Non-Chinese organizations, such as the U.S. Department of Energy and the Netherlands Environment Agency, produce widely cited CO[SUB]2[/SUB] estimates for China (among other countries), but these are also based on the national energy data.
A study published last month by a China-U.K.-U.S. team in Nature Climate Change spotlighted a large disparity in estimates of Chinese CO[SUB]2[/SUB] emissions when the numbers were based on national energy statistics versus summed provincial data. To illustrate the contrast, those researchers had applied a standardized U.N. protocol for estimating the emissions of any developing country by sector.
The new Harvard-Nanjing study goes deeper, however, constructing a "bottom-up" emission inventory that is specific to China's energy and technology mix. It combines the results of Chinese field studies of CO[SUB]2[/SUB] emissions from diverse combustion processes with a plant-by-plant data set for power generation, independent research on transportation and rural biomass use, and provincial-level energy statistics for the remaining sectors.
The Harvard-Nanjing team believes provincial energy data to be more accurate than national statistics because the provincial data have been empirically tested in peer-reviewed atmospheric studies that compare the expected emissions of conventional air pollutants to actual instrumental observations by satellites and ground stations. Provincial statistics also take into account the large quantities of coal produced by small, illegal mines.
"There are several different ways to estimate emissions of greenhouse gases or air pollutants, from those designed to support policy processes to those made by scientists researching atmospheric transport and chemistry," explains co-author Chris Nielsen, Executive Director of the Harvard China Project, which is based at SEAS.
The former methods suit the needs of policy, attributing emissions to identifiable sources for actionable controls, but the latter are often more environmentally accurate, according to Nielsen.
"The methods used by atmospheric scientists can be more complete, incorporating new research on dispersed sources that are poorly represented in official statistics or weakly targeted by policy -- such as the burning of crop wastes in fields or biofuels in poor, rural homes," Nielsen explains. "The data are also more detailed in spatial terms. This allows a comparison of emission estimates to the pollution levels measured at the surface, or from space, testing the underlying energy data in the process."
The new study capitalizes on prior tests and a bottom-up data framework that has been demonstrated for conventional air pollutants to produce a more thorough estimate of China's CO[SUB]2[/SUB] emissions.
The new study also quantifies the uncertainty of the emission totals, applying formal statistical methods. For instance, the team found that the 95% confidence interval for the 2005 CO[SUB]2[/SUB] estimate lies between