Ozone layer depletion and climate change affecting each other and wreaking havoc on many natural systems, says study
Damage of the ozone layer - which protects the Earth from the sun’s harmful ultraviolet radiation - is now playing a direct role in climate change, which in turn is adversely impacting many natural systems. Changes in regional climate, caused in part by ozone depletion, for example, are threatening the habitat and survival of a number of species found only in the Southern Hemisphere, reveals a new study.
While ozone depletion has long been known to increase harmful UV radiation on the Earth’s surface, its effect on climate has now becoming evident. The new study shows that the ozone layer is emerging as a crucial player in driving climate change.
The study states that increased penetration of solar radiation through the depleted ozone layer is interacting with changing climate, and the “consequences are rippling through the Earth’s natural systems”, impacting everything from weather to the health and abundance of sea mammals like seals and penguins.
The findings of the study have been detailed in a review article in Nature Sustainability by members of the United Nations Environment Programme or UNEP's Environmental Effects Assessment Panel, which informs parties to the Montreal Protocol. Thirty-nine researchers contributed to the review article.
“What we are seeing is that ozone changes have shifted temperature and precipitation patterns in the Southern Hemisphere, and that is altering where the algae in the ocean are, which is altering where the fish are, and where the walruses and seals are. So we are seeing many changes in the food web,” said Kevin Rose, a researcher at Rensselaer Polytechnic Institute. Rose serves on UNEP's Environmental Effects Assessment Panel and is a co-author of the review article.
The report also found that climate change may also be affecting the ozone layer in terms of how quickly it can recover. Greenhouse gas emissions, for example, trap more heat in the lower atmosphere leading to a cooling of the upper atmosphere, which researchers say is slowing the recovery of the ozone layer.
The 1987 Montreal Protocol on Substances that Deplete the Ozone Layer - the first multilateral environmental agreement to be ratified by all member nations of the United Nations - was designed to protect the ozone layer by phasing out the production of harmful human-made substances.
According to estimates, the ozone layer is projected to recover to pre-1980 levels by the middle of the 21st century. Earlier this year, however, researchers reported detecting new emissions of ozone-depleting substances emanating from East Asia, which could threaten this recovery.
The Environmental Effects Assessment Panel - which is one of the three scientific panels to support the Montreal Protocol - focused in particular on the effects of UV radiation, climate change, and ozone depletion in their review article.
The report points to the Southern Hemisphere, where a hole in the ozone layer above Antarctica has pushed the Antarctic Oscillation - the north-south movement of a wind belt that circles the Southern Hemisphere - further south than it has been in roughly a thousand years. The movement of the Antarctic Oscillation is, in turn, directly contributing to climate change in the Southern Hemisphere.
As climate zones have shifted southward, rainfall patterns, sea-surface temperatures, and ocean currents across large areas of the Southern Hemisphere have also shifted, impacting terrestrial and aquatic ecosystems, say the findings. The effects, say the researchers, can be seen in Australia, New Zealand, Antarctica, South America, Africa, and the Southern Ocean.
“It is now clear that ozone depletion is directly contributing to climate change across much of the Southern Hemisphere by altering atmospheric circulation patterns in this part of the globe, which affect weather conditions, sea surface temperatures, ocean currents and the frequency of wildfires in multiple regions. These ozone-driven changes in climate are in turn exerting impacts on terrestrial and aquatic ecosystems in this region,” says the paper.
In the oceans, for example, some areas have become cooler and more productive, where other areas have become warmer and less productive, the study found. “Warmer oceans are linked to declines in Tasmanian kelp beds and Brazilian coral reefs, and the ecosystems that rely on them. Cooler waters have benefitted some populations of penguins, seabirds, and seals, who profit from greater populations of krill and fish,” the findings reveal.
The report says that on land, changing patterns of rainfall have resulted in increased agricultural productivity in some regions (for example, southeastern South America) and drought conditions in others (for example, Chile).
Drier conditions have resulted in increased salinity in lakes and changed lake fauna in East Antarctica and the eastern Andes. “On the Antarctic Peninsula, the productivity of terrestrial ecosystems has increased with warmer and wetter conditions, whereas productivity in East Antarctica has responded negatively to cooling and drying,” says the paper.
The study also says that changes in ultraviolet radiation and climate can further affect human health by modifying air quality. Several recent international assessments have concluded that poor air quality is the largest global cause of deaths due to environmental factors.
“Modelling studies for the US indicate that reductions in UV radiation due to stratospheric ozone recovery will lead to lower ground-level ozone in some urban areas but slight increases elsewhere. Although these changes in ground-level ozone are estimated to be small, large populations are already affected by poor air quality, such that even small relative changes in air quality could have consequences for public health,” says the article.