Tropical cyclones like hurricanes and typhoons could move to the north and south in their respective hemispheres because the planet is warming because of human carbon dioxide emissions scientists say.
2020’s subtropical hurricane Alpha is the first tropical storm to be seen that made landfall in Portugal as well as this year’s hurricane Henri that struck land in Connecticut could be the harbingers of such storms.
“This is a significant and under-appreciated danger from warming temperatures,” says first author Joshua Studholme, a physicist at Yale University’s Earth and planet sciences department. He was also an author of the United Nations’ Intergovernmental Panel on Climate Change sixth assessment report, which was released in the spring of this year.
“This research suggests that in the 21st century’s tropical storms are likely to occur in a larger area of latitudes than what’s been the norm on Earth over the past three million years,” Studholme says.
A rise in the number of tropical cyclones is often considered to be a sign of climate change however, much is not clear about how sensitive they are to our global average temperature.
The 1980s saw coauthor of the study Kerry Emanuel of the Massachusetts Institute of Technology employed principles from classical thermodynamics in order to predict that warming of the planet would lead to more severe hurricanes–a prediction that was verified by observations.
Other aspects of the connection between tropical cyclones and climate aren’t based on physical science. For instance, there’s no consensus among scientists on the extent to which storms will grow or decrease when the temperature rises or the reason the earth experiences around 90 of these events per year.
“There is a great deal of uncertainty about how tropical cyclones are likely to alter in the near future,” says Alexey Fedorov who is a professor of oceanic and atmospheric science at Yale. “However numerous research studies suggest that we may observe more tropical cyclones at mid-latitudes even if the frequency of all tropical cyclones doesn’t increase and is currently being debated.
“Compounded by the expected rise in the average intensity of tropical cyclones this result suggests greater dangers from tropical cyclones as Earth’s temperature increases climate.”
Tropical cyclones typically form in lower latitudes, which have access to warm water from tropical oceans , and are protected from the shearing impacts of jet streams – the west-to east bands of wind that encircle the globe. The rotation of Earth causes clusters of thunderstorms to condense and create the vortices that eventually become tropical hurricanes. Other mechanisms for hurricane formation are also present.
As the temperature rises the temperature difference between Equator and poles could diminish as the scientists say. In the summer the weakening of the jet stream could cause or even a splitting of the jet stream, which could open an opportunity at mid-latitudes to allow tropical cyclones to develop and grow in intensity.
In the course of their research Studholme Fedorov along with their coworkers studied numerical simulations of warm climates of Earth’s distant past, current satellite observations, as well as a range of climate and weather projections, and the fundamental physics of atmospheric convection and the planetary-scale wind.
For instance, they observed that climate simulations of warmer temperatures in the Eocene (56 to 34 million years ago) and Pliocene (5.3 to 2.6 million years earlier) times witnessed tropical cyclones develop and increase in intensity in higher elevations.
“The most important issue in making the future predictions for hurricanes is that the models used for forecasts of climate don’t have enough resolution to accurately simulate tropical cyclones” says Studholme as a postdoctoral researcher at Yale.
“Instead various different, indirect methods are usually employed. However, they appear to alter the nature of how tropical cyclones develop and grow. Many of these techniques offer predictions that are in contradiction to one another.”
The study draws its conclusions from analyzing relationships between hurricane physics on scales that aren’t depicted in the current climate models as well as the more accurate simulation of the jet streams on Earth and the north-south air circulation, also known by the Hadley cells.