East Asian CO2 level change caused by Pacific Decadal Oscillation

Accurate projection of CO2 concentration in time and space remains challenging because of complex interplay between anthropogenic emissions, biospheric responses, and climatic variabilities. While the increase of atmospheric CO2 concentration is due primarily to fossil fuel burning, natural climate variabilities are known to introduce intermittent changes in the global CO2 growth rates. Thus, understanding the correlation of climate and carbon cycling systems is important in assessing the anthropogenic and natural impacts. Here, we report decadal CO2 variabilities in western Pacific based on data from several ground-based stations in the region and Atmospheric Infrared Sounder (AIRS). In addition to the well-established El Nino-Southern Oscillation (ENSO), there exists a decadal changing CO2 trend in the datasets mentioned above. Analysis of ground-based CO2 measurements in northern Taiwan shows a decadal signal at amplitudes of -5 ppm. In contrast, AIRS shows a similar trend but at a reduced amplitude of -1 ppm. We attribute the decadal signal to dynamical factors related to the Pacific Decadal Oscillation (PDO). This decadal signal, however, is not reproduced by the state-of-the-art data assimilation system, CarbonTacker, suggesting a gap in our knowledge of the modulation of carbon cycling systems and climate.