The study investigates the relationship between thermal tolerance breadth (TTB) and latitude in ectothermic animals, accounting for habitat, hemisphere, methodological differences, and taxonomic affinity. The authors found that TTB generally increases with latitude, with a greater rate of increase in the Northern Hemisphere. Terrestrial ectotherms show a consistent decrease in lower thermal limits with latitude, while marine species exhibit a poleward decrease in both upper and lower thermal limits. The findings support hypotheses from smaller taxonomic subsets and geographical scales, highlighting differences between terrestrial and marine ectotherms in how thermal physiology varies with latitude. These differences may be related to the degree of temperature variability experienced on land and in the ocean. The study provides a comprehensive global analysis, addressing analytical challenges and using modern statistical techniques to account for multiple sources of variation.The study investigates the relationship between thermal tolerance breadth (TTB) and latitude in ectothermic animals, accounting for habitat, hemisphere, methodological differences, and taxonomic affinity. The authors found that TTB generally increases with latitude, with a greater rate of increase in the Northern Hemisphere. Terrestrial ectotherms show a consistent decrease in lower thermal limits with latitude, while marine species exhibit a poleward decrease in both upper and lower thermal limits. The findings support hypotheses from smaller taxonomic subsets and geographical scales, highlighting differences between terrestrial and marine ectotherms in how thermal physiology varies with latitude. These differences may be related to the degree of temperature variability experienced on land and in the ocean. The study provides a comprehensive global analysis, addressing analytical challenges and using modern statistical techniques to account for multiple sources of variation.