Assessing Climate Extremes Indices Over Global Drylands Under Real World Warming Beyond 1.5°C: Spatial Distribution and Temporal Trends

Abstract

Since July 2023, the monthly global mean surface temperature (GMST) has consistently surpassed a 1.5°C rise compared to pre-industrial levels. At this critical period, where real world warming exceeds 1.5°C, it is urgent to assess extreme climate signals in climate-sensitive regions to understand the impacts of global warming. This study aims to explore the spatial distributions and temporal trends of 17 extreme temperature and precipitation indices defined by the Expert Team on Climate Change Detection and Indices (ETCCDI) from 1985 to 2023 for global drylands, utilising ERA5 daily reanalysis data. It is found that all temperature indices demonstrate significant warming trends across most drylands. In 2023, the annual maxima/minima of daily maximum/minimum temperatures (TXx/TNn) increase above 3°C in the drylands of North America, North Africa, and the Arabian Peninsula compared to the baseline period (1985–2014). These drylands experience notable increases in the frequency of warm days/nights (TX/N90p) and summer days (SU), along with a lengthening of warm spell duration (WSDI), as well as decreases in the frequency of cool days/nights (TX/N10p) and frost days (FD). On dryland average, all high (low) extreme temperature indices in 2023 surpass (fall below) their corresponding 1985–2014 averages. Three-quarters of dryland-averaged extreme temperature indices (TXx, FD, SU, TX/N90p, TX/N10p and WSDI) in 2023 all break their records since 1985. Notably, five indices, including WSDI, TX/N90p and TX/N10p, emerge as the most sensitive to the high GMST. The temporal trends of extreme precipitation indices are less significant and weaker in magnitude than those of extreme temperature indices. When averaged across drylands, three extreme precipitation intensity indices in 2023 are located within one standard deviation range of their averages during the reference period. Two duration-based extreme precipitation and drought indices suggest an exceptionally extended and enhanced dry situation over drylands in 2023. Meanwhile, most drylands reveal considerable spatial variability in 2023 compared to 1985–2014.