Implications of alternative assumptions regarding future air pollution control in scenarios similar to the Representative Concentration Pathways

These scenarios combine low and high air pollution variants of the scenarios with radiative forcing targets in 2100 of 2.6 W m⁻² and 6.0 W m⁻². Simulations using the global atmospheric chemistry and transport model TM5 for the present-day climate show that both climate mitigation and air pollution control policies have large-scale effects on pollutant concentrations, often of similar magnitude.

If no further air pollution policies would be implemented, pollution levels could be considerably higher than in the RCPs, especially in Asia. Air pollution control measures could significantly reduce the warming by tropospheric ozone and black carbon and the cooling by sulphate by 2020, and in the longer term contribute to enhanced warming by methane.

These effects tend to cancel each other on a global scale. According to our estimates the effect of the worldwide implementation of air pollution control measures on the total global mean direct radiative forcing in 2050 is +0.09 W m⁻² in the 6.0 W m⁻² scenario and −0.16 W m⁻² in the 2.6 W m⁻² scenario.