1. Budyko, M. I. The Heat Balance of the Earth’s Surface (National Weather Service, U.S. Department of Commerce, 1958).
2. Middleton, N. & Thomas, D. World Atlas of Desertification (Wiley, 1997).
3. Palmer, W. C. Meteorological Drought (US Department of Commerce, Weather Bureau, 1965).
4. Vicente-Serrano, S. M., Beguería, S. & López-Moreno, J. I. J. Climate 23, 1696–1718 (2010).
5. Seneviratne, S. I. et al. in Climate Change 2021: the Physical Science Basis (eds Masson-Delmotte, V. P. et al.) 1513–1766 (Cambridge Univ. Press, 2021).