Precipitation Seasonality Amplifies as Earth Warms

Precipitation exhibits a pronounced seasonal cycle, of which the phase and amplitude are closely associated with water resource management. While previous studies suggested an emerged delaying phase in the past decades, whether the amplified amplitude has emerged is controversial. Using multiple observational data sets and climate simulations, here we show that the amplification of precipitation annual cycle has emerged in most global land areas since the 1980s, especially in the tropics. These amplifications are mainly driven by anthropogenic emissions, and will be further intensified by 17.6% in the future (2081–2100) under high emission scenario (Shared Socioeconomic Pathways, SSP585), and limited to 7.2% under SSP126 scenario, relative to the historical period (1982–2014). Precipitation seasonality will be amplified by 4.2% for each 1°C of global warming, which is seen in all emission scenarios. The mitigation of lower emissions is helpful for alleviating the amplification of precipitation seasonality in a warming world. Plain Language Summary Precipitation displays pronounced seasonal cycle, and its phase and amplitude are closely associated with ecosystems and our society by redistributing water resources. The phase of precipitation cycle has been well understood in previous studies, but how its magnitude changes remain largely unknown. In this study, we use multiple observational data sets and climate simulations to show that precipitation annual cycle has been amplified in most parts of global land area since the 1980s. These amplifications are especially strong in the tropical regions, and are mainly driven by the increases in anthropogenic greenhouse gas and aerosol emissions. In the future (2081–2100) under high emission scenario (SSP585), they will be further intensified by 17.6% relative to the historical period (1982–2014), and will be limited to 7.2% under low emission scenario (SSP126). We also estimate that the amplitude of precipitation seasonality will be increased by around 4.2% for each 1°C of global warming, and suggest that keeping lower emissions is helpful for alleviating the amplification of precipitation seasonality. Key Points Precipitation annual cycle has been amplified in most global land areas since the 1980s, especially in the tropics Precipitation seasonality amplification will be intensified in the future, mainly driven by anthropogenic emissions The amplitude of precipitation seasonality will be amplified by ∼4.2% for ea