The contributions of short-lived climate pollutants to global cliamte change since the pre-industrial era

Abstract:

Short-lived climate pollutants (SLCPs), a set of compounds with shorter lifetimes than well-mixed greenhouse gases, cause warming effect on climate. We used an online aerosol–climate model (BCC_AGCM2.0_CUACE/Aero) to simulate the total effective radiative forcing (ERF) and climate response to the changes in SLCP concentrations, including methane, tropospheric ozone, and black carbon, from the pre-industrial era to the present. The global annual mean ERF of SLCP was 0.99 [0.79-1.20] W m^–2. Increased SLCP concentration led to warming effects over most parts of the globe, with the most obvious warming occurring in the mid-high latitudes of the Northern Hemisphere (NH) and the ocean around Antarctica, showing increases reaching 1.0 K. The changes in annual mean surface air temperature (SAT) caused by SLCP were more prominent in the NH (0.78 [0.62–0.94] K) than in the Southern Hemisphere SH (0.62 [0.45–0.74] K). SLCP have caused precipitation to increase by about 0.10 mm d^–1 in mid-high latitudes and decreased by about 0.20 mm d^–1 in subtropical regions. There was a northward shift in the Intertropical Convergence Zone (ITCZ) due to the interhemispheric asymmetry in SAT, which was an adverse effect induced by aerosols. Changes in SLCP concentrations caused increases in global annual mean SAT and precipitation of 0.70 K and 0.02 mm d^–1, respectively. It is found in this work that SLCP had little effect on global average cloud cover. But the SLCP-induced cloud cover changes over regional scales are not negligible. SLCP has caused low cloud cover to increase by about 2.5% over high latitudes in the NH and the ribbon area near 60°S, whereas high cloud cover increased by more than 2.0% over northern Africa and the Indian Ocean. Finally, we compared the ERFs and global and regional warming effects of SLCP and carbon dioxide (CO₂). From 1850 to the present, the SLCP ERF was equivalent to 66%, 83%, and 50% of that of CO₂ in global, NH, and SH mean, respectively. The increases in SAT caused by SLCP were 43% and 52% of those by CO₂ over the globe and China, respectively.