Desert dust exerts a substantial longwave radiative forcing missing from climate models

Abstract

Historical increases in desert dust have affected climate by perturbing Earth’s energy balance, including through interactions with longwave radiation that remain poorly quantified. Here, we use a data-driven analytical model to estimate the global dust longwave direct radiative effect (DRE). Our results align with observational estimates of longwave radiative effects, constraining the present-day global longwave DRE to +0.25 ± 0.06 Wm⁻² (90% confidence interval). Climate models underestimate the longwave DRE by approximately a factor of two because they underestimate super coarse dust and neglect dust scattering of longwave radiation. We also show that increased dust since preindustrial times generated a positive longwave direct radiative forcing peaking at +0.14 ± 0.07 Wm⁻² in the 1980s, modestly enhancing greenhouse warming. Because this warming is largely missing from current climate models, incorporating it could reduce biases in net aerosol forcing, refine climate sensitivity estimates, and improve projections of future climate change.