Leighton is an early-career scientist who is building a career in model evaluation under uncertainty. His analysis of large perturbed parameter ensembles of climate models has identified the main causes of variance in cloud-active aerosol concentrations and aerosol radiative forcing. This research has shaped the approach in climate science to designing perturbed parameter ensembles and has identified priorities for development in the UK Earth System Model. He has developed and implemented statistical methods for densely sampling model uncertainty and constraining that uncertainty using multiple measurement datasets. Leighton’s research has also identified climatically important model deficiencies that affect model skill at making climate projections.