Will the 'evapotranspiration paradox' phenomenon exist across China in the future?

The uneven changes in potential evapotranspiration (PET) in response to temperature rise are called the 'evapotranspiration paradox' phenomenon, which is expected to intensify further under a warming climate. In this paper, we explored the spatial-temporal changes in the future 'evapotranspiration paradox' phenomenon over China and its 10 major river sub-regions under different climate change scenarios. Thus, this paper uses four global climate model outputs under seven shared socioeconomic pathway-based scenarios (SSP1-1.9, SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP4-3.4, SSP4-6.0 and SSP5-8.5) from the sixth phase of the Coupled Model Intercomparison Project (CMIP6). Considering the latest IPCC's 6th Assessment Report (AR6), this research emphasizes the 2021-2040 (near-term), 2041-2060 (mid-term) and 2081-2100 (long-term) periods to anticipate the 'evapotranspiration paradox' phenomenon. In this study, PET is estimated based on the modified Penman-Monteith (P-M) method (considering CO2). Furthermore, the paradox phenomenon in this study is defined considering two pivotal conditions: the surface temperature increases but the evaporation decreases (Type I), and the temperature decreases but the evaporation still tends to increase (Type II). The results show that there were only Type I 'evapotranspiration paradoxes' that existed in the historical period, which were dominant especially before the 1990s. Nearly 50% of the areas experienced the Type I 'evapotranspiration paradox' phenomenon that occurred during 1975-1994 and 1995-2014. Spatially, it covered 100% of the area of the Southeast River (SER) and the Liaohe River (LR) during 1975-1994 and the area of the SER, the HAR, the HHR and the LR during 1995-2014. In the future, the interdecadal growth rate of PET in China is projected to be the highest under the SSP5-8.5 and the lowest under the SSP3-7.0 with spatial variation. Importantly, the largest areas of approximately 36% and 45% with the Type I phenomenon are inclined to occur under the SSP1-1.9 and SSP4-6.0, respectively, over the long-term period (2081-2100). The area with the Type I phenomenon will be less than 20% in the near-term, and it is less than 12% in the mid-term period. For the Type II evapotranspiration paradox, the uppermost 45% of the area is expected to experience the Type II phenomenon under SSP1-1.9 during the mid-term period, while it is 30% under SSP1-2.6 during the long-term period. However, this study's findings provide the scientific basis for formulating adaptation and mitigation strategies to combat 'evapotranspiration paradox'-related extremes at regional scales.

Automated summary

This paper explores the spatial-temporal changes in the future 'evapotranspiration paradox' phenomenon over China and its major river sub-regions. The results show that this paradox phenomenon has existed historically and is expected to intensify in the future under different climate change scenarios. The findings provide a scientific basis for formulating adaptation and mitigation strategies at regional scales.