The annual cycle is one of the most important components of the global climate system Yet little attention has been paid to the response of the equatorial annual cycle to anthropogenic climate change. Here we present results from a global climate model with high tropical resolution that simulates a strong intensification of the annual cycle in the tropical Pacific in response to increased greenhouse gas concentrations. This sensitivity of the tropical annual cycle to greenhouse warming can be explained in terms of tropical ocean-atmosphere feedbacks. A possible amplification of the tropical annual cycle is expected to have also profound ecological and societal impacts.