Projected changes in mild weather frequency over China under a warmer climate

Abstract

Previous studies largely focus on changes in mean climate state and climate extremes under a warmer climate, and little is known about changes in mild weather, which is a positive and pleasant condition and is highly related to human outdoor activities. Although changes in observed mild weather frequency over China and their drivers have been revealed, the understanding of how mild weather evolves with projected warming is still limited. Here, we examine future changes in mild weather frequency over China based on comprehensive thermal comfort indices and dynamically downscaled climate projections produced by the Regional Climate Model version 4 (RegCM4) within the framework of Coordinated Regional Climate Downscaling Experiment - Coordinated Output for Regional Evaluations (CORDEX-CORE). We demonstrate that changes in mild weather frequency in a warmer future exhibit remarkable regional discrepancy. Particularly, the densely populated southeastern China will experience a robust decrease in mild weather relative to the current level, although a general increasing trend is observed in this area during the past decades. On a seasonal scale, the decrease in mild weather in summer overwhelms the increase in spring and autumn, and this is more prominent in warmer regions. For the drivers, it is suggested that changes in mild weather frequency are dominated by elevated temperatures, with little contribution from relative humidity, wind speed, and sunshine duration.

Front Matter

“…We reviewed several studies that focused on mild weather conditions using various indices such as thermal comfort (25 ), good weather (26 ), comfortable days (23 ), thermal comfort condition (20, 21 ), outdoor thermal comfort (24 ), mild weather (17 -19 ), and mild days (16 ). However, these studies are geographically limited to a few regions, such as Sydney ( 25), Washington D.C and New York (26 ), Indiana ( 16), China (17,19,21,23 ), and Singapore urban park (24 ). In addition, there is a limited understanding of how pleasant weather conditions could respond to anthropogenic climate change.…”

Detection and Attribution of Human‐Perceived Warming Over China

“…For model simulations, in addition to the trend for MME, we also calculated trends for individual models. If at least one significant individual trend differs in the sign of the ensemble mean trend, it is considered as “uncertain”; if the “uncertain” condition is not fulfilled and less than half of the individual trends are significant, it is considered as “negligible”; otherwise, the modeled signals are referred to as “robust” (J. Zhang et al., 2022).…”

Inequality of Global Thermal Comfort Conditions Changes in a Warmer World

“…To assess the possible effects of individual variables (i.e., temperature, relative humidity, and wind speed) on the changes in thermal comfort conditions, the comfortable/uncomfortable days were recomputed using a method similar to the “factor separation method” (Lin et al., 2019; Wu et al., 2017; Zhang, You, Ren, et al., 2022). In each computation, we allowed one variable to evolve across the time but keep others at the climatological levels (i.e., the mean over the reference period of 1995–2014).…”

“…In a hot environment, for instance, the human body may produce or absorb more heat than it dissipates, thus increasing its core temperature to values that can potentially cause discomfort, heat‐related illnesses, and ultimately death (Kovats & Hajat, 2008; Sailor et al., 2019). Furthermore, mild weather, which describes a condition that is neither too cold nor too hot (i.e., comfortable), is also of great societal significance; for example, human outdoor activities such as tourism, sports, building construction, and transport can benefit from mild weather (Lin et al., 2019; van der Wiel et al., 2017; Zhang, You, Ren, et al., 2022).…”

“…According to previous studies, the potential for compound heat‐humidity extremes to cause unprecedented discomfort conditions under a warming climate is an issue of growing concern (e.g., Luo & Lau, 2021; Raymond et al., 2020; Sherwood & Huber, 2010; Sylla et al., 2018; F. Wang & Zhang, 2019). The number of cold discomfort days is projected to decrease (Gao et al., 2018; J. Li et al., 2018; W. Li et al., 2022; Zhang, You, Ren, et al., 2022; Zhang, You, Wu, et al., 2022), although extreme cold events are likely to persist across continents even under the 21st‐century warming scenarios (Kodra et al., 2011; Zhu et al., 2019). Besides, compared with the efforts focused on the change of mean climate state and climate extremes, less attention has been paid to the behavior of mild weather.…”