Fig. 4: Probability density for the Ship minus NoShip difference.

The probability densities are estimated over the shipping lane grid cells for the annual a lightning density (strokes km⁻² yr⁻¹), b altitude (km) of the mid-to-high cloud top, and c radius (μm) of the low cloud droplets. They are calculated through the Gaussian Kernel Density Estimation method. The gray, red, blue, and green curves are the differences for the pre-regulation climatology (2012–2019), 2012–2015, 2016–2019, and 2020–2023, respectively. The solid, dashed, dotted, and dash-dotted lines represent various p-values. Shadings and filled circles indicate the 95% confidence intervals of the distributions. The three legends across the three panels are applicable to each of the three panels. The figure was created using Matplotlib Python package.