Zim scientists shine . . . discover ‘ozone hole’ over South Africa

Sifelani Tsiko Senior Writer
A team of Zimbabwean researchers has discovered an “ozone hole” over South Africa that is centred over the Free State Province during spring, which impacts on temperature and rainfall levels, according to findings published in the Journal of Frontiers in Earth Science.

Lead author, Professor Desmond Manatsa, a climate science expert at Bindura University of Science Education (BUSE) and his colleague, Professor Geoffrey Mukwada from Free State University made these stunning revelations whilst working under the “Afromontane Research Unit Project” that is based at the Free State University of South Africa.

Ozone (O3) is an “allotrope” of oxygen — a form of oxygen that is different to O2, the gas that makes up 21 percent of the atmosphere.

Ozone is formed from oxygen in a reversible reaction.

The ozone layer is the part of the upper atmosphere where ozone is found in the highest concentrations.

The ozone there absorbs ultraviolet radiation, preventing most of it from reaching the ground. This is important because ultraviolet radiation can lead to skin cancer.

In simple terms, it is a shield high in the sky protecting us from potentially lethal solar radiation.

Prof Manatsa and Prof Mukwada found that when the ozone hole develops in certain spring seasons, the temperatures are observed to rise significantly and while drying the region especially the Free State Province.

But when the “ozone hole” fills up considerably, the sub-region becomes cooler and wetter. These novel findings constitute the strongest evidence yet that ozone has a significant direct impact on the climate of South Africa.

South Africa’s “Ozone Hole,” ever to be discovered over any continent outside the polar regions represents a discovery that is “at the frontier of science” and has recently been published in the Journal of Frontiers in Earth Science.

“This research was prompted by the steep contrast on the heat from the sun that was rather ‘scorching’ during my spring season visit to Free State University in 2015 compared to the subsequent same period visit in 2017 when the sun appeared cooler,” said Prof Manatsa, a gold medal recipient of the Japanese Society for the Promotion of Science (JSPS) award for Ozone Impact Research on Southern Africa

“What puzzled me is that this unexplained sun’s heating difference between the two periods could easily be distinguished on one’s skin especially in October under similar clear sky and calm.

“That is when it occurred to us that there should be something within the clear skies that was allowing the sun’s heat to significantly filter through in 2015 while considerably eating up the heat from the sun in 2017. We then reasoned that the most likely gas with such propensity to alter the energy coming from the sun under clear sky and calm conditions should be ozone.”

The ozone layer resides in the stratosphere (upper part of the atmosphere) which surrounds the entire Earth. This layer considerably absorbs the ultraviolet (UV-B) radiation from the Sun.

As a result, the amount of UV-B reaching Earth’s surface is greatly reduced, hence basically the ozone layer acts as a shield to protect the Earth.

However, Prof Manatsa said, when depleted more UV-B filters in to heat the lower atmosphere and the surface where it has been found in this research to have a direct impact on the climate of South Africa.

Prof Manatsa

On the other hand, ozone’s depletion in the ozone layer may have dire consequences on the well being of the community as it allows more UVB to reach the surface of the earth. It has been known that human exposure to relatively large amount of UV-B increases the risk of skin cancer, cataracts, and a suppressed immune system and can also damage terrestrial plant life and aquatic ecosystems.

“Ozone depletion has always been a global issue needing urgent attention. For example, just over 30 years ago, when scientists discovered an environmental crisis that was attributed to the ozone hole over the Antarctica (South Pole), policies were quickly put in place to ban the offending chemicals popularly known as the ozone depleting substances under the auspices of the Montreal Protocol of 1987 and its subsequent amendments,” said Prof Manatsa.

This protocol has since been ratified by 196 states and the European Union, making it the first treaty in United Nations history to be universally adopted. As a result there is now growing evidence indicating that the Montreal Protocol is working as intended.

“Now it appears that as the ozone hole has taken a backseat in the minds of the public, a fresh crisis appear to have arisen, adding a new dimension to the already known perils of climate change over South Africa,” the Zimbabwean climate expert said.

“The ozone hole is not technically a “hole” where there is virtually no ozone, but is actually a region of exceptionally depleted ozone in the upper part of the atmosphere(stratosphere). Unlike to the causes for the development of the ‘ozone hole’ over the Antarctic where the depletion is caused by chemical reactions that are enhanced by the ozone depleting substances, that over South Africa has been linked to the Brewer Dobson circulation.”

This circulation, he noted, is more pronounced during Southern Hemisphere spring (August–October) where it transports ozone in the stratosphere from the tropics to the subtropics, the region of South Africa’s location.

The “ozone hole” that is centred over Free State of South Africa, develops when this circulation is enhanced in some years thereby rapidly transporting more ozone diluted air, as what has occurred more often after 1997 due to global warming.

Prior to 1997, he said, the “ozone hole” was not that apparent since the transported air had predominantly adequate ozone concentrations.

“As such, as long as global warming intensifies, so does the ozone hole over South Africa. This means that the ozone depletion cannot yet be ticked off the country’s environmental watch list,” Prof Manatsa said.

“Unlike the chemical ozone depletion which is being reduced through limiting the emissions of ozone depleting substances under the Montreal Protocol, climate change is also confounding the way this environmental issue can be scientifically tackled as it is the global warming which appears to deepen the ozone hole over South Africa by enhancing the Brewer Dobson circulation.

“This makes it unrealistic to expect the spring ozone layer over South Africa to ever return to its pre-depletion state (pre 1997) without solving global issues related to restricting global warming.”

While the South African government works itself into frenzy about environmental issues, this demonstrated evidence entails that they should not ignore the situation above the country’s clouds.

“When you see such local discoveries, you don’t have to start debating statistics. It appears in this work the scientists have demonstrated their case very clearly.

“As such we must do the needful by probing deeper rather than brush it aside as just one of those usual research findings’, said one of the experts familiar with this work.

“We now hope that we can find yet additional impacts of the ‘ozone hole’ on the health of society, agriculture and ecosystems during the period, that outside what we demonstrated on the impacts on temperature and rainfall”, said co-author Prof Mukwada.

source:the herald

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