In a new study, an international team of scientists has found that the plants in China absorb a third of its carbon emissions.
According to a report in Nature News, similar work has been done for the United States, but this study provides the first comprehensive analysis of China's terrestrial carbon uptake, which is critical for calculating the country's net emissions.
Led by Shilong Piao, an ecologist at Peking University in Beijing, the team estimated carbon uptake during the 1980s and 1990s using three different methods: ecosystem modelling, plant and soil inventories, and an analysis of atmospheric CO2 trends.
The authors estimate a net carbon sink of between 0.19 and 0.26 billion tonnes of carbon per year, which translates to 28 to 37 percent of China's emissions during the period in question.
"Everyone has been scrambling around to come up with an estimate for China, because we don't have a lot of information," said Kevin Gurney, a climate researcher at Purdue University in West Lafayette, Indiana.
"They really have been methodologically thorough. They have tackled it from three different angles, and the nice thing is that all three of those converge on the same estimate," he added.
"This is an impressive paper," said Gregg Marland, a climate researcher at Oak Ridge National Laboratory.
He credits the researchers with analyzing the question in three ways and getting a fair amount of agreement in their results.
"In spite of that, there is still a considerable amount of uncertainty, and that uncertainty cascades through the system," he said.
Although studies such as this can give broad estimates of carbon uptake, Marland said that the only way to pin down some of these numbers might be via satellites, like the Orbiting Carbon Observatory that plunged into the sea earlier this year.
"It's going to be a long while before we have the kind of satellite data that we want," he added.