世界气象组织：2021年科学联合报告（英文版）

Greenhouse Gas Concentrations in the Atmosphere WMO GAW Global Climate in 2017�2021 � WMO Global GHG Emissions and Budgets GCP • Concentrations of the major greenhouse gases – CO2 , CH4 , and N2 O – continued to increase in 2020 and the first half of 2021. • Overall emissions reductions in 2020 likely reduced the annual increase of the atmospheric concentrations of long-lived greenhouse gases, but this effect was too small to be distinguished from natural variability. • Reducing atmospheric