Decreasing emissions of NO_x relative to CO_2 in East Asia inferred from satellite observations

摘要

At present, global CO_2 emission inventories are mainly based on bottom-up estimates that rely, for example, on reported fossil fuel consumptions and fuel types~(1,2). The associated uncertainties propagate into the CO_2-to-NO_x emission ratios that are used in pollution prediction and monitoring~3, as well as into biospheric carbon fluxes derived by inverse models4. Here we analyse simultaneous and co-located satellite retrievals from SCIAMACHY (ref. 5; SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY) of the column-average dry-air mole fraction of CO_2 (refs 6,7) and NO_2 (refs 8-10) for the years 2003-2011 to provide a top-down estimate of trends in emissions and in the ratio between CO_2 and NOx emissions. Our analysis shows that the CO_2-to-NO_x emission ratio has increased by 4.2 - 1.7%yr~(-1) in East Asia. In this region, we find a large positive trend of CO_2 emissions (9.8 - 1.7%yr~(-1)), which we largely attribute to the growing Chinese economy. This trend exceeds the positive trend ofNO_x emissions (5.8-0.9%yr~(-1)). Our findings suggest that the recently installed and renewed technology in East Asia, such as power plants, transportation and so on, is cleaner in terms of NO_x emissions than the old infrastructure, and roughly matches relative emission levels in North America and Europe.