The Impact of Eastern Pacific Warming on Future North Atlantic Tropical Cyclogenesis

Tropical cyclogenesis in the Atlantic is influenced by environmental parameters including vertical wind shear, which is sensitive to forcing from the tropical Pacific. Reliable projections of the response of such parameters to radiative forcing are key to understanding the future of hurricanes and coastal risk. One of the least certain aspects of future climate is the warming of the eastern tropical Pacific Ocean. Using climate model experiments isolating the warming of the eastern Pacific and controlling for other factors including El Nino-Southern Oscillation (ENSO), changes in Atlantic tropical cyclogenesis potential by the end of this century are & SIM;20% lower with enhanced eastern Pacific warming. The ENSO signal in Atlantic tropical cyclogenesis potential amplifies with global warming, and that amplification is larger with enhanced eastern Pacific warming. The largest changes and dependencies on eastern Pacific warming are found in the south-central main development region, attributable to changes in zonal overturning. Today, there are about 15 tropical storms per year in the Atlantic. That number varies considerably from year to year, with El Nino being one major factor. When the eastern Pacific Ocean warms temporarily, Atlantic hurricanes tend to be suppressed (and vice versa for La Nina). As the climate warms due to greenhouse gas emissions, hurricanes are expected to change. Such changes could include the average number of tropical storms per year, where they tend to form, how strong they become, how far and fast they travel, how much rain they produce, and how El Nino affects them. This study investigates how the formation regions of Atlantic hurricanes may change in the future, particularly as a function of how much the eastern Pacific Ocean warms in the future, which is one of the most uncertain aspects of climate change. We find that the warming of the eastern Pacific strongly influences predictions of future changes in Atlantic hurricanes, including how El Nino affects them. Specifically, a strong eastern Pacific warming causes a change in the winds over the tropical Atlantic, which shifts where hurricanes will tend to form in the future, and increases the effect of El Nino. Enhanced surface warming in the eastern equatorial Pacific Ocean impacts the response of Atlantic hurricanes to global warmingGenesis potential decreases in the south-central part of the main development region, but only with enhanced eastern Pacific warmingThe El Nino/La Nina signal in Atlantic genesis potential amplifies with global warming-more so with enhanced eastern Pacific warming