Abstract Tropical cyclones (TCs) can be considered as Carnot heat engines, where thermodynamic efficiency depends on the sea surface temperature (SST) and TC outflow temperature ( T o ) in the upper atmosphere. This study investigates how TC efficiency in the western North Pacific (WNP) Ocean varies under different El Niño‐Southern Oscillation (ENSO) conditions: the Eastern Pacific (EP), the Central Pacific (CP), and the Mixed El Niño types, as well as La Niña. We also explore how these changes affect a TC's theoretical upper bound (potential intensity (PI)). Using a reanalysis data set from 1979 to 2024, we find that TC efficiency decreases during La Niña, due to warmer T o , and increases during CP El Niño, where upper‐level cooling dominates. EP and Mixed El Niño show more heterogeneous responses. These efficiency changes contribute to PI variability from −38 to +27%, depending on ENSO type and region.
Liao et al. (Wed,) studied this question.