Atmospheric scientists from Harvard University and Nanjing University said their data for 2005 to 2009 provided the first statistically rigorous estimates of China's CO2 emissions.
"China's emissions of CO2 are of central concern in efforts to combat global climate change," said lead author Yu Zhao, a former postdoctoral researcher at Harvard SEAS now at Nanjing University.
"But despite all of the attention to China's CO2 emissions, they're less well quantified than most people realize."
China has only once officially estimated its CO2 emissions, based on national energy statistics from 1994, a Harvard release reported Friday.
The Harvard–Nanjing study combines the results of Chinese field studies of CO2 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 release said.
Emissions calculated "top-down," based on annual national energy statistics that are released by the Chinese government, suit the needs of policy by linking emissions to identifiable sources for policy action but are often less environmentally accurate, co-author Chris Nielsen of Harvard said.
"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.