Under current global weather conditions, tropical cyclones occur across specific stretches of the world’s tropical oceans. With climate change, all the factors controlling tropical cyclogenesis may be altered. The twentieth century has already witnessed global warming, punctuated by a warm spell in the 1930s. The response of the atmosphere to these past events in terms of production of tropical cyclones is only imperfectly known. The area second only to the western North Pacific in frequency of tropical cyclones is the eastern North Pacific. The climatology of tropical storm activity for this region for the period since 1900 is being assembled in hopes that it may provide insight into the role of global warming in tropical cyclogenesis, not only earlier this century but into the next.