15:30 〜 15:45
[AAS11-01] Declining Black Carbon Contribution from China to the Arctic
キーワード：黒色炭素エアロゾル、北極、中国の貢献、モデル、観測
Black carbon (BC) aerosols significantly contribute to Arctic warming. Around 2010, China accounted for ~27% of the Arctic BC burden via long-range transport. However, China’s BC emissions have declined substantially since 2010 due to clean air policies, likely reducing its Arctic contribution. Meanwhile, climate variability may have influenced BC transport efficiency.
To assess these effects, we used a global chemistry-transport model with the ECLIPSEv6b emission inventory to simulate China’s BC contribution to the Arctic from 2009 to 2022. Two experiments were conducted: a standard simulation reflecting temporal emission changes and a sensitivity run with Chinese BC emissions fixed at 2010 levels. The standard simulation revealed significant declines in China’s Arctic BC contribution across all seasons and altitudes, with the largest absolute decreases during the haze season and at mid-troposphere levels. However, relative decline rates remained consistent across seasons and altitudes. The sensitivity simulation estimated that China’s emission reductions accounted for 51–64% of the declining trends in China’s Arctic BC contribution, with the remainder possibly attributed to climate-driven transport changes.
The standard simulation also showed contrasting trends in total Arctic BC: a decline during the haze season but an increase in summer. The latter is likely due to rising biomass burning. These changes were more pronounced at the surface than in the mid-troposphere. The sensitivity simulation indicated that China’s emission reductions contributed 19%, 48%, and 38% to the declining trends in total Arctic haze-season BC at the surface, mid-troposphere, and column levels, respectively.
Observed aerosol absorption coefficients at four Arctic observatories also declined significantly during the haze season, with steeper trends where modeled China-to-total BC ratios were higher. This provides observational evidence of China’s reduced BC contribution to the Arctic, likely mitigating its radiative forcing impact.
To assess these effects, we used a global chemistry-transport model with the ECLIPSEv6b emission inventory to simulate China’s BC contribution to the Arctic from 2009 to 2022. Two experiments were conducted: a standard simulation reflecting temporal emission changes and a sensitivity run with Chinese BC emissions fixed at 2010 levels. The standard simulation revealed significant declines in China’s Arctic BC contribution across all seasons and altitudes, with the largest absolute decreases during the haze season and at mid-troposphere levels. However, relative decline rates remained consistent across seasons and altitudes. The sensitivity simulation estimated that China’s emission reductions accounted for 51–64% of the declining trends in China’s Arctic BC contribution, with the remainder possibly attributed to climate-driven transport changes.
The standard simulation also showed contrasting trends in total Arctic BC: a decline during the haze season but an increase in summer. The latter is likely due to rising biomass burning. These changes were more pronounced at the surface than in the mid-troposphere. The sensitivity simulation indicated that China’s emission reductions contributed 19%, 48%, and 38% to the declining trends in total Arctic haze-season BC at the surface, mid-troposphere, and column levels, respectively.
Observed aerosol absorption coefficients at four Arctic observatories also declined significantly during the haze season, with steeper trends where modeled China-to-total BC ratios were higher. This provides observational evidence of China’s reduced BC contribution to the Arctic, likely mitigating its radiative forcing impact.