According to carbonbrief.org the most cited climate-change related paper in 2021 explores the mortality related to heat.
Vicedo-Cabrera, A.M., Scovronick, N., Sera, F. et al. The burden of heat-related mortality attributable to recent human-induced climate change. Nat. Clim. Chang. 11, 492–500 (2021). https://doi.org/10.1038/s41558-021-01058-x
You can read it on NATURE website.