Future haze events in Beijing, China: When climate warms by 1.5 and 2.0°C

Cuiping Liu,Lijuan Miao,Yadong Lei,Quan Yang,Feng Zhang

doi:10.1002/joc.6421

Abstract

AbstractChina is the world's second‐largest economy, and its capital Beijing has been suffering from severe haze pollution in recent years. However, how the winter haze events in Beijing vary under different global warming scenarios is still open for debate. In order to analyse long‐term winter haze characteristics in Beijing in the future, we have simulated haze events using the haze weather index (HWI) for the warming periods of 1.5 and 2.0°C, based on 20 Coupled Model Intercomparison Project Phase 5 (CMIP5) models under two representative concentration pathways (RCP4.5 and RCP8.5). Our results indicate that 16 CMIP5 models have preferable performance in simulating the spatial pattern and occurrence frequency of winter haze events in Beijing. We highlight that in the 1.5 and 2.0°C global warming period (2020s–2050s), Beijing will face a significant increasing trend (6–9% growth rate) in the occurrence of winter haze events compared with the reference period (1986–2005). The frequency of winter haze events under the RCP4.5 increases less than under the RCP8.5 in the 1.5°C warming period but is closer to RCP8.5 in the 2.0°C warming period. The increase of winter haze events with respect to natural factors in Beijing could be attributed to stronger atmospheric inversions, weaker East Asian winter monsoons, and a shallowing East Asian trough induced by global warming. Our results will provide scientific instructions for environmental departments to better face meteorological hazards, such as air pollution episodes, thereby improving the early warning mechanism system for global warming.

Highlights

| MethodologyWe focus on the frequency of haze events during boreal winter (December, January, and February), as this period typically experiences the most severe haze events in Beijing (Niu et al, 2010; Ding and Liu, 2013)
Different from previous studies, surprisingly, we found that the 2.0C warming will not lead to significant increases in the frequency of haze events relative to the 1.5C warming, especially in RCP8.5
This study aimed to predict the occurrence of winter haze events in Beijing under 1.5 and 2.0C global warming scenarios based on the National Centers for Environmental Prediction (NCEP) dataset and Coupled Model Intercomparison Project Phase 5 (CMIP5) model simulations; and depict meteorological factors related to winter haze events using haze weather index (HWI) index

Summary

| Methodology

We focus on the frequency of haze events during boreal winter (December, January, and February), as this period typically experiences the most severe haze events in Beijing (Niu et al, 2010; Ding and Liu, 2013). 250 hPa Air temperature Air temperature meteorological elements are normalized to ΔT, V850, and U500: The ΔT considers the anomaly of temperature difference between the upper and lower troposphere and is expressed in the following formula: ΔT. When U500 > 0, an anomalous wind field of westerly wind strengthening in the north and weakening in the south of Beijing, bringing about an unfavourable situation for convection development and horizontal dispersion These three anomalies are all referenced to the historical daily climatology and normalized by the historical standard deviation to facilitate comparison between the historical and future climate. The reference period is 0.6C warmer than the preindustrial level (IPCC, 2013), which translates the global warming targets of 1.5 and 2C as warmings of 0.9 and 1.4C relative to the reference period level, respectively

| RESULTS

Findings

| DISCUSSION

| CONCLUSION