China’s carbon balance increases the political pressure

With talk of the need for global cutbacks in greenhouse gas emissions, and the reluctance of some developing countries to reduce their fossil fuel consumption when North America and Europe are largely responsible for the problem of anthropogenic climate change, it’s worthwhile looking at the numbers involved. We now have an estimate of China’s carbon balance.

In this week’s Nature is a paper by a group of environmental scientists which looks at the carbon balance of terrestrial ecosystems in China. Peking University ecologist Shilong Piao, together with colleagues in China and France, analysed the carbon balance during the 1980s and 90s using biomass and soil carbon inventories, ecosystem models and atmospheric inversions, and found a net sink of between 0.19 and 0.26 billion tonnes of carbon per year. To put these figures into context, global ecosystems absorbed carbon at a rate of 1–4 billion tonnes per year during the same period. This offsets some 10–60% of fossil fuel emissions.

Looking at the results in more detail, the new findings suggest that north-eastern China is a net source of atmospheric carbon dioxide, resulting from over-harvesting and degradation of forests. Southern China, on the other hand, accounts for more than 65% of the country’s carbon sink. This, say the researchers, can be attributed to regional climate change, large-scale plantation programmes and shrub recovery.

With the next round of global climate treaty negotiations beginning in December of this year in Copenhagen, the political ramifications of this latest scientific research will be profound. However, as pointed out by Purdue University carbon ecologist Kevin Gurney in an accompanying Nature News & Views commentary, the Chinese carbon offset is very likely to diminish as the country continues to emit more and more fossil fuel-created carbon dioxide each year.

Based on an estimate of carbon emissions for 2007, the average uptake estimated by Piao et al. would reduce the the overall fossil-fuel CO2 emissions by 10–15%. And, according to projections from the International Energy Agency, in 2030 only 6–8% of carbon emissions will be offset by the biospheric uptake discussed in the Nature paper. The implication is that, unless China curbs its fossil-fuel use, the terrestrial carbon sink will be of little help in the grand scheme of things.

Further reading

“The carbon balance of terrestrial ecosystems in China”, Piao et al., Nature, 458, 1009 (2009)

“China at the carbon crossroads”, Kevin Robert Gurney, Nature, 458, 977 (2009)