Hand in Hand Tropical Cyclones and Climate Change: Investigating the Response of Tropical Cyclones to the Warming World

Abstract

What are the primary factors governing Tropical Cyclone Potential Intensity (TCPI) and how does the TCPI vary with the change in CO2 concentration are the two fundamental questions we investigated here. In the first part, a strong spatial correlation between the TCPI and the ocean temperature underneath was used to develop a statistical model to quantify the TCPI over the remote regions where the tropical cyclone related observations are difficult to acquire. The model revealed an overall increase in the TCPI when the atmospheric CO2 concentration was doubled. Finally, the study examines the TCPI’s sensitivity on the ocean temperature (at the spatial scales). Two independent models (HADCM3 from Met Office, UK and GFDL-CM3 from GFDL, NOAA, USA) on an average reveals an increase in the TCPI between 8 to 10 m/s per unit increase in the ocean temperature (in degree C). The key finding to emerge from this study is that the increase in the TCPI responds comparatively weakly to the increasing ocean temperature when CO2 amount is increased. We call this observation as, “the sensitivity saturation effect”. According to our findings, the TCPI responds weakly (become less sensitive) to the ocean temperature on doubling the CO2 concentration. This effect was observed in all the ocean basins and in both the considered climate models. Though the TCPI show a rise in increasing the CO2 concentration but, its response to the SST decreases. This observation leads to a set of next level questions for instance, will there be a sensitivity saturation effect, analogous to the well-known “Band Saturation effect”, on increasing the CO2 levels and if it does, will the TCPI’s sensitivity plateau? If it plateaus, at what cut-off CO2 levels would that happen? These emerging questions open up a new area of investigation for the climatologists and the enthusiasts in the related fields. In this manner, this part of the research provides a framework for the future exploration of the subject.