Climate Change and Air Quality in Southeastern China: Hong Kong Study

Abstract

As climate change continues to unfold over the next several decades in response to increasing levels of greenhouse gases (GHGs) in the atmosphere, the effects of climate change and future air quality will be more noticeable and observable. Understanding future climate and air quality has become one of the highest priorities for many countries and individual cities, where mitigation and adaptation could be planned. In Hong Kong, local government has pledged to reduce the GHG emissions by 60–65% from the 2005 level (i.e., 40 million tonnes CO₂ equivalent (CO₂e) in 2005) by 2030. The reduction focuses mainly on local energy saving, alternative transportation, and green energy generation. As Hong Kong moves into less carbon-intense technologies in both transportation and energy sectors, this much needed change will benefit the city’s local air quality. Currently, no long-term carbon reduction plan for 2050 has been identified in the government.

In terms of future air quality projections, strong relationships between emissions and pollutant concentrations have been observed in Southeastern China under the IPCC AR5 scenarios, where the reduction of regional emissions (e.g., SO₂, NOx, and PM) has a great effect on future PM_2.5 air quality. Overall, PM_2.5 air quality over Pearl River Delta region has shown a clear improvement in 2050 under RCP8.5 emission scenario, with a mean concentration reduction of 5–15% (up to 12 μg/m³). For ozone, a slight increase (i.e., 0–3%) of annual mean has been projected, which may be due to the combined effect of slow emission reduction of NMVOCs and less NOx titration in the VOCs limited regime. In addition, some studies also projected the increase of typhoons tracking near Taiwan Strait in the future climate would increase the occurrence of summer ozone episodes in Hong Kong.