Ozone depletion was a factor even before CFCs were widely used

Current satellite data measures ozone separately in the lower, middle, and upper stratosphere, and model simulations help scientists determine the causes of any changes in these layers. This is the possibility that we think we are adding to the world of the 1950s.

Early detection

The researchers ran a climate model that included the chemistry of ozone, feeding history of greenhouse gases, ozone depletion, and natural phenomena such as volcanic eruptions. After laying the groundwork with a few simulations from 1850, he ran many simulations from 1950 onwards with slightly different starting points in space to create different realizations.

Detecting ozone depletion depends on both the intensity of the situation and the intensity of the noise. The lower and middle layers of the stratosphere respond very strongly to things like volcanic eruptions – and we have the 1963 eruption of Mount Agung to deal with.

Ozone in the upper stratosphere does not change much, and is also affected by ozone-depleting pollutants. Although the effects of these pollutants are strongest in the middle of the high latitudes, the variability is much smaller near the tropics. In this example, this is where the process of ozone depletion began.

If we changed our modern scientific instruments in 1950, ozone depletion would have started to be detected (with a 95 percent confidence level) in the upper stratosphere in the tropics around 1957. At this time, half of the two-thirds of the ozone-eating chlorine in the upper atmosphere was less carbon tetrachloride than carbon tetrachloride.

Elsewhere, it would have taken much longer. By 1976, it would be known in the lower stratosphere—including in Antarctica, where the ozone hole wasn’t discovered until a decade later.

So it seems that ozone depletion was recognized much earlier than it was discovered, which means that we may have acted sooner and stopped the loss of ozone.

However, the researchers also point out that this type of surveillance is currently under threat. The satellite currently measuring ozone at several locations high in the stratosphere has been around since 2004 and is well past its use-by date. (Last year’s White House budget the petition demanded that they closein fact.) Without a replacement, it will be very difficult to detect future changes while they are still small.

PNAS, 2026. 10.1073/pnas.2608286123 (About DOIs).