Total ozone measured by the OMPS Nadir Mapper on February 17, 2023. Credit: NASA/NOAA/JPSS
An international research team has quashed claims of a large, permanent ozone hole in the tropics, concluding that there has been no significant long-term decline in the layer that traps ultraviolet radiation1.
The researchers, including Jayanarayanan Kuttippurath at the Indian Institute of Technology in Kharagpur, West Bengal, analysed ground-based, ozonesonde and satellite ozone measurements to examine depletion and spatiotemporal trends between 1980 and 2022.
The team used statistical methods to assess trends and compared their findings with a previous study that suggested severe ozone depletion in the tropics. They found that average ozone levels in these regions, including India, remain well above the critical threshold of 220 Dobson Units used to define the ozone hole.
“The slight decrease observed in the tropical ozone in recent decades is due to the changes in atmospheric dynamics, not because of chemistry,” says Kuttipurath.
The earlier study relied on inadequate data, primarily from surface to 11km altitude which is insufficient to accurately assess ozone levels at the critical 15–20km altitude, according to the researchers. Ozone holes are confined to Antarctica due to unique conditions such as extreme cold, strong polar vortex and polar stratospheric clouds, they say.
