Warming-driven lower-tropospheric stratification intensifies ducting over global oceans

Under global warming, the marine atmospheric boundary layer shows an increase in lower-tropospheric stratification. These thermodynamic shifts alter vertical refractivity gradients and can modulate atmospheric ducts, which are natural waveguides crucial for beyond-line-of-sight electromagnetic propagation. Using ERA5 reanalysis data from 1940 to 2025, we find a global-scale intensification of atmospheric ducts over oceans at mid- to low-latitude, with a robust increasing trend in atmospheric duct occurrence probability, strength and top height. Mechanistically, this intensification is intrinsically coupled with the sustained increase in static stability in the marine atmospheric boundary layer. Although interannual climate modes, such as the El Niño/Southern Oscillation, modulate these anomalies, the long-term warming trend dominates the long-term trend. Ultimately, continuous warming is shifting the marine atmospheric background state towards a highly stratified regime favouring more frequent and intense ducting, with implications for global maritime communication, radar and navigation systems. Atmospheric ducts are waveguides that affect electromagnetic propagation in the atmosphere, affecting radar and other technologies. Here the authors show that warming intensifies such ducting over mid- to low-latitude oceans.