Vegetation Greening Offsets Urbanization-Induced Fast Warming in Guangdong, Hong Kong, and Macao Region (GHMR)

Previous studies show that the environment in the Guangdong, Hong Kong, and Macao region is under the double stress of global warming and urbanization. Here, we show that due to the increase of regional greenness, the effect of urbanization warming on surface air temperature (SAT) decreased with time and became statistically insignificant from 2004 to 2018, compared to 1979 onward; while the urbanization itself has significantly warmed land surface temperature (LST), with a warming rate of 0.14 degrees C 0.04 degrees C/10a at daytime and 0.02 degrees C 0.02 degrees C/10a at nighttime during 2004-2018, respectively. The anthropogenic heat was found to have a limited influence on SAT, but more significant and tangible effects on LST. It is essential to improve the control of additional warming effects caused by urbanization. Plain Language Summary The Guangdong, Hong Kong, and Macao region is the most economically developed region in China, and the urbanization impact on the regional warming is frequently discussed during recent decades. We found that the urbanization warming on surface air temperature (SAT) has decreased to insignificant during the recent decade due to regional greening, while the warming of land surface temperature (LST) remains tangible. This result is related to the different effects of two moderating drivers (anthropogenic heat and vegetation index) on both SAT and LST. Thus, it is essential to increase urban greenness and reduce anthropogenic heat fluxes in parallel. Key Points The effect of urbanization on the surface air temperature (SAT) decreases over time as regional vegetation greening increases The urbanization effect on the land surface temperatures (LSTs) from the long time series of satellite retrievals remains significant The anthropogenic heat was found to have a limited influence on SAT, but more significant and tangible effects on LST