A new study indicates that the 21st century may see an expansion of hurricanes and typhoons into mid-latitude regions, which include major cities such as New York, Boston, Beijing and Tokyo.
“This research predicts that the 21st century’s tropical cyclones will likely occur over a wider range of latitudes than has been the case on Earth for the last 3 million years,” said Joshua Studholme, author of the study.
While an increase in tropical cyclones is commonly cited as a signal of climate change, much remains unclear about how sensitive they are to the planet’s average temperature. Study co-author Kerry Emanuel used concepts from classical thermodynamics to predict that global warming would result in more intense storms – a prediction that has been validated in the observational record. However, there is no agreement among scientists about whether the total number of storms will increase or decrease as the climate warms, or why the planet experiences roughly 90 such events each year.
Generally, tropical cyclones form at low latitudes that have access to warm waters from tropical oceans and away from the shearing impact of the jet streams – the west to east bands of wind that circle the planet.
As the climate warms, temperature differences between the poles and the Equator will decrease, the researchers say. In summer months, this could cause weakening or even a split in the jet stream, opening a window in the mid-latitudes for tropical cyclones to form and intensify.
For the study, Studholme and colleagues analyzed numerical simulations of warm climates from Earth’s distant past, recent satellite observations, and a variety of weather and climate projections, as well as the fundamental physics governing atmospheric convections and planetary-scale winds.
“The core problem when making future hurricane predictions is that models used for climate projections do not have sufficient resolution to simulate realistic tropical cyclones,” said Studholme. “Instead, several different, indirect approaches are typically used. However, those methods seem to distort the underlying physics of how tropical cyclones form and develop. A number of these methods also provide predictions that contradict each other.”
The new study finds its conclusions by examining connections between hurricane physics on scales too small to be represented in current climate models and the better-simulated dynamics of Earth’s jet streams and north-south air circulation, known as the Hadley cells.
https://phys.org/news/2022-01-future-hurricanes-roam-earth.html