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 Niño–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.