New progress and enlightenment on different types of drought changes from IPCC Sixth Assessment Report

This paper reviews the definition and type of droughts, as well as their driving factors, historical changes, attributions and projections based on the Working Group I (WGI) contribution to the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6) on the physical science basis of climate change. The IPCC AR6 new results show that: (1) The changes in meteorological and agricultural droughts are not significant on a global scale, but display an increasing trend in some regions. The increasing trend shows that anthropogenic climate change plays an important role in exacerbating droughts. For meteorological droughts, the understanding of the influence of human activities is of low confidence. (2) Agricultural and ecological droughts in most regions can be attributed to human activities (medium to high confidence); for hydrological droughts, in addition to human-induced climate change, regional water resources management and land use are also important factors (medium confidence). (3) In the future projections, more regions around the world will experience more severe and frequent drought events in the future. Agricultural and ecological droughts will also become more frequent and intense as the temperature rises. (4) In the analysis of assessment of changes in different types of droughts, the key variable of atmospheric evaporation demand (AED) is emphasized. Changes in AED are not only a direct response to climate warming, but also a driving factor for drought changes, affecting the physiological processes of vegetation. Meanwhile, changes in AED also feedback to evapotranspiration. The interactions between different types of droughts will become more complicated under the background of intensifying climate change. In the future, the research and operational service of droughts in China should deepen our understanding of connections between changes of different types of droughts, strengthen multi-disciplinary cooperation and explore feedback loops between drought changes, local human activities and ecological processes based on multiple datasets and various evidences.