Will extreme temperature events emerge earlier under global warming?

The increased frequency of climate extremes in recent years has profoundly affected terrestrial ecosystem functions and the welfare of human society. Previous studies have mainly focused on the impact of the frequency and intensity of climate extremes, but these studies have rarely documented the emergence time of climate extremes. Will extreme temperature events emerge earlier under global warming? To address this question, in this study, we focused on the emergence times of temperature extremes in China. Five indices were selected to quantify the trends in the emergence times of temperature extremes, including the annual maximum temperature and minimum temperature emergence dates, the <0 <degrees>C and >= 10 degrees C start dates, and the >= 10 degrees C end date. Additionally, the dynamic changes in extreme temperature emergence times and the influencing factors were analyzed. The results showed that from 1960 to 2018, the annual maximum and minimum temperature emergence dates showed no significant advancing trends in China. The >= 10 degrees C start date showed a significant advanced trend (P < 0.001), while the <0 degrees C start date and the >= 10 degrees C end date showed significant delayed trends (P < 0.01). The Qinghai-Tibet Plateau and the northwestern regions of China were the regions where the <0 degrees C start date and the >= 10 degrees C end date were most significantly delayed. Additionally, the changes in the emergence dates of temperature extremes were correlated with atmospheric circulation patterns. The change in the <0 <degrees>C start date showed a significant positive correlation with the Southern Oscillation index (P < 0.001) and the Western Pacific Subtropical High intensity index (P < 0.01). The >= 10 degrees C start date trend showed a significant negative correlation with the Northern Hemisphere Subtropical High area index (P < 0.01) and the Western Pacific Subtropical High intensity index (P < 0.05). The variation in extreme temperature emergence times showed a dependence on topographic factors. The maximum temperature emergence date and the <0 <degrees>C start date were delayed more significantly at higher elevations and latitudes in China. These results provide reference information for studying changes in extreme temperature emergence dates and taking measures to reduce the losses caused by temperature extremes.