Lightning in global chemistry-climate models: A review of parameterizations, evaluations, and future projections

Abstract. Chemistry-climate models are our main tool to project how global lightning activity may change in a warmer world. However, the spatial and temporal scales involved in cloud electrification are too small to be explicitly resolved, so lightning is typically simulated using empirical relationships with proxy variables such as cloud top height (CTH), convective precipitation, convective available potential energy times precipitation, or upward ice flux. This review summarizes existing global lightning parameterizations, their skill in reproducing observed lightning patterns, and their projected future changes.

We identify 16 parameterizations (including some variants) that have been applied in global modelling studies, with CTH — the earliest developed — remaining the most widely used. Most parameterizations predict total lightning, while cloud-to-ground lightning is rarely computed directly. Several parameterizations, including CTH, reproduce observed spatial lightning patterns reasonably well (r > 0.7), whereas precipitation-based methods perform worse (r often < 0.6). Most approaches underestimate lightning over central Africa and in mid-to-high latitudes, while overestimating activity over the Amazon and Maritime Continent. They also struggle to capture the observed land-ocean contrast in lightning activity and tend to underestimate temporal variability from diurnal to inter-annual scales.

Future projections show large uncertainty, ranging from an 11 % decrease to a 44 % increase in lightning frequency per degree global warming. The mean across all parameterizations is +4.4±7.6 % K^-1, while the mean across all projections (which are strongly biased towards CTH) is +7.5±7.9 % K^-1. Although there is a broad agreement that lightning activity will increase in high latitudes, the tropical response remains highly uncertain.