Owing to global warming, there are suggestions that the tropopause has risen and will continue to rise, the troposphere has warmed, and these phenomena may have an effect on ozone concentrations in the lower stratosphere. Furthermore, greenhouse gas-induced climate change appears to be causing an increase in upwelling in the tropics, which could decrease stratospheric ozone there, according to simulations. The exact mechanism responsible for these changes has yet to be identified, but the data is clear: the “100% recovery by 2100” prediction didn’t include these results. With this new understanding, that recovery may be stalled or pushed out to extremely long timescales, and global warming may be exacerbating or even causing this trouble. As the Ball et al. paper states:
[A] rise in the tropopause, due to the warming troposphere, could lead to a decrease in ozone at mid-latitudes, but the tropopause rise is also affected by the ozone loss itself…
where ozone in the lower stratosphere is an important factor in radiative forcing of the climate. Based on straightforward physics, reducing lower-stratospheric ozone will offset some of the forcing increase from rising GHGs.
In other words, redistributing the ozone away from the lower stratosphere has actually reduced the radiative forcing that accelerates global warming. Yes, the hole in the ozone layer over Antarctica may be shrinking, but we have to examine the global effects of ozone, not just what’s occurring at one pole. And when we do, it doesn’t look good. The overall concentrations of ozone in the atmosphere, worldwide, have not increased since 1997, but are the same today as they were back then. As Ball and his collaborators state:
The Montreal Protocol is working, but if the negative trend in lower stratospheric ozone persists, its efficiency might be disputed. Restoration of the ozone layer is essential to reduce the harmful effects of solar UV radiation that impact human and ecosystem health. Presently, models do not robustly reproduce the decline in lower stratospheric ozone identified here. This will be imperative, both to predict future changes and to determine if it is possible to prevent further decreases.
If we are to restore the ozone layer and reduce the harmful effects of ultraviolet radiation of life on planet Earth (including to humans), we have to figure out what’s causing this odd behavior. Whether you’re a fan of current climate models or not, getting it right is essential to understanding our world, and keeping it hospitable for not only humans, but for the ecosystems our planet depends on. We only have one planet where life has arisen and sustained itself, as far as we know. It’s up to all of us to take care of it.