Number of tropical cyclones is declining, study shows
A new study based on reanalysis data finds that the number of tropical cyclones, also known as hurricanes, has been declining since the early 20th century. Image: Chand et al, Nature Climate Change 2022
For the first time, researchers have shown that the annual number of tropical cyclones declined in the 20th century compared to the late 19th century. a study published in natural climate change.
Using historical and model data, this paper – by Suzanne CamargoExtreme weather experts from the Columbia Climate Institute’s Lamont-Doherty Earth Observatory said the number of storms globally and regionally decreased by about 13 percent during the period.
However, the authors of the study caution that frequency is only one aspect of controlling the risks associated with tropical cyclones.These storms have increased intensity In recent decades, it may also be shift Proximity to coastal areas with a growing population.
Tropical cyclones are large systems of low pressure that form over tropical waters when underlying environmental conditions such as sea surface temperature and wind shear are suitable. These include extreme rainfall and high winds, as well as coastal hazards such as damaging waves, storm surges, estuarine flooding and coastal erosion.
It is unclear how tropical cyclones change under human emissions, as ocean warming is expected to exacerbate storms, while some changes in atmospheric circulation are thought to prevent storms from forming. Providing historical context is challenging because the observational record is incomplete, especially before 1950.
Although short-term data have been studied, these studies have led to conflicting conclusions about how tropical cyclone numbers will change as a result of global warming.
“To see trends in any tropical cyclone characteristic, such as cyclone frequency, tropical cyclone intensity or distribution, you need long-term data,” said lead author Savin Chand of the Commonwealth University of Australia.
The record was incomplete until the advent of satellites that provided the most reliable and consistent methods for studying tropical cyclones. “Only hurricanes that affect people’s lives are known and reported,” Camargo explained.
The new study attempts to overcome this blind spot by relying on ground pressure data, collected more uniformly by weather stations and ships over the years, she added. Scientists ran these pressure data through climate models to simulate hurricanes since 1850.
Using reconstructed records and climate model data, they were able to reveal annual declines in tropical cyclone numbers on global and regional scales since 1850. For most tropical cyclone basins, this decline has accelerated since warming became unprecedented in the 1950s.
However, the latest findings suggest that the number of hurricanes in the North Atlantic Basin has increased in recent decades. This may be because the basin is recovering from a decline in tropical cyclone numbers caused by human-related aerosol emissions in the late 20th century. However, the number of storms per year is still lower than in the pre-industrial period.
These findings support research showing that current climate change is causing a reduction in the number of tropical cyclones.
However, Camargo said the debate over how climate change affects tropical cyclone numbers is not over — scientists need to better understand how tropical cyclones form in the first place.
“This study is yet another piece of information about this debate. In my opinion, only a more comprehensive understanding of the origins can ‘resolve’ this debate, so we are talking about years of research and many papers, not a single paper,” she said.
Adapted from the story of the Commonwealth University of Australia
