Cropland Exposed to Drought Is Overestimated without Considering the CO 2 Effect in the Arid Climatic Region of China.

Drought seriously restricts people's lives and social–economic development. An accurate understanding of the evolution of drought characteristics and future changes in cultivated land exposure can reduce the risk of drought. There is evidence that increased CO₂ concentrations alter the physiological properties of vegetation and, thus, affect drought evolution. In this study, both changes and differences in drought (i.e., characteristics and cropland exposure) with and without the CO₂ effect over the arid region of China are investigated, using seven CMIP6 outputs and land-use under seven shared-socioeconomic-pathway (SSP)-based scenarios. The results show that: (1) drier conditions will be more severe in 2015–2100 under SSP5-8.5, especially if the CO₂ effect is neglected. Moreover, the CO₂ effect will increase with increasing emission concentrations; (2) drought intensity will be greater than in the baseline period (1995–2014, approximately −1.45) but weaker than that without the CO₂ effect under all scenarios; (3) drought frequency will decrease, and will generally decline faster if the CO₂ effect is not considered; (4) drought duration will increase and the difference between the presence and absence of the CO₂ effect will always be smallest under SSP1-1.9 and largest under SSP5-8.5; (5) drought acreage will also increase, and neglecting the CO₂ effect is always higher than that considering CO₂. The difference between the two algorithms will increase with time; and (6) cropland exposure to drought will increase, and can even reach 669,000 km² and 524,000 km² considering and ignoring the CO₂ effect, respectively. Our findings suggest that ignoring CO₂ in drought evaluations will result in significant overestimations of drought projections. [ABSTRACT FROM AUTHOR]