Figure 4

Linear trends (μg m⁻³ decade⁻¹) of (a) the model simulated and (b) normalized DJF mean PM_2.5 concentrations over the North China Plain contributed by the North China Plain, rest of China and foreign emissions for 1980–2000 and 2000–2014. Time series of predicted PM_2.5 concentrations (μg m⁻³), averaged over the North China Plain, contributed by the North China Plain, rest of China and foreign emissions under (c) RCP4.5 and (d) RCP8.5 emission scenarios. Linear trends of predicted PM_2.5 concentrations (μg m⁻³ decade⁻¹) over 2020–2030, 2030–2040 and 2040–2050 contributed by the North China Plain, rest of China and foreign emissions under (e) RCP4.5 and (f) RCP8.5.