Wilson, A., N. Lutsko, D. F. Dias and A. J. Miller, 2026:
Projections of Earth’s Hottest Surface Temperatures in
CMIP6.
Geophysical Research Letters, in press.
Abstract.
Earth’s hottest near-surface air temperatures provide a benchmark for the upper tail of
land heat extremes. Using CMIP6 simulations, we evaluate historical extremes against
Berkeley Earth and project future changes under SSP2-4.5 and abrupt-4×CO2. Historical
fidelity is assessed from the spatial pattern of the 99th percentile of daily maximum
temperature (p99 Tmax) over land using centered RMSE, mean bias, and spatial R2. We
analyze three annual tropical land indices: tropical land-mean temperature (TTL), dailymean
temperature on the hottest day each year (TDM), and the maximum daily-maximum
temperature (TDX). Across models, TDM and TDX warm 30–40% faster than TTL in transient
trends and equilibrium responses, consistent with amplified upper-tail warming. Hotspotfrequency
maps of the annual global land maximum show persistence in subtropical arid
and semi-arid regions. We define a fixed-threshold record-like benchmark for hottest-land
temperature and relate exceedance likelihood to tropical land warming; pooled fits show
exceedance odds rise ∼35% per 1 ◦C.
Preprint (pdf)