Ozone And Climate Change

Ozone gas is made from the combining of three oxygen atoms. Its molecular structure is (O3) as opposed to the normal oxygen that we breathe which is (O2). The ozone layer is a protective layer of gas that naturally occurs high up in the air, in the lower stratosphere.

The ozone gas is formed from the splitting of an oxygen molecule by the rays of the sun, specifically ultra violet rays. This separates the oxygen molecules with each individual atom reacting with another oxygen molecule to make three atoms sharing a covalent bond. This is what makes ozone.

The earth’s atmosphere is divided into several layers. The first and lowest is the troposphere followed by the stratosphere. The stratosphere is where majority of ozone is located, at 10 to 50 kilometers above the earth’s surface. Ozone is a very important gas, without which life on earth would be non-existent.









By its reaction with sun rays, it absorbs solar ultraviolet rays and so prevents them from reaching the earth where they would cause harm to human health and destruction to the natural world. In this way, it protects us.

Ozone is formed naturally from the action of lightning on an oxygen molecule, causing splitting and recombination, which is what occurs during rainstorms. It is the smell of the earth after the new rains.  Ozone is also produced from the volatile organic compounds or the oxides of nitrogen reacting with oxygen. The two are pollutants and come from vehicle exhaust, power plants, paint, chemical factories and car repair shops among others. Ozone however is a dangerous gas at ground level. This is because as a pollutant, it brings respiratory problems, reacting with the cells and biological makeup of the respiratory tract.

Ozone is a unique gas because of its properties and connection to climate change. First of all, it is a greenhouse gas and like all other greenhouse gases it absorbs heat and warms up the planet. So, at ground level and as tropospheric ozone, it influences climate change.

The second connection is that climate change is caused by greenhouse gases, of which one of them is a group known as fluorinated gases. This includes chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). These manmade gases however are unique because they both destroy ozone and are greenhouse gases.

The Montreal Protocol on Substances That Destroy The Ozone Layer was formed in 1987, to protect the ozone layer from harmful substances. Known as Ozone Depleting Substances (ODS), these include halons, CFCs and HCFCs. Chlorine and bromine as an element destroys the ozone layer by reacting with ozone and forming other compounds. This is the primary cause behind the formation of the ozone hole.

In fact, a single atom of chlorine can destroy slightly more than a hundred thousand molecules of ozone. These gases had to be regulated and replacements found, which is why hydrofluorocarbons (HFCs) were invented to replace chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). HFCs don’t contain chlorine and use fluorine instead.

The second part is that CFCs, HCFCs and HFCs are strong greenhouse gases. CFCs and HCFCs have a very high global warming potential, reaching tens of thousands above that of carbon dioxide. So the protocol did well for climate by banning the use of the stronger HCFCs and CFCs but also became a part of climate change through the replacement HFCs.

So, in order to regulate hydrofluorocarbons and their strong impact on climate, the Montreal Protocol had to be amended. This was done in Kigali, Rwanda in 2016 where replacements for HFCs were proposed. This includes hydro olefins. A timetable for the phasing out of HFCs was also agreed on: industrialized nations would start cutting down on production and use by 2019, developing nations would do so by 2024 and a particular group of countries that experience high temperatures would stop usage by 2028. Emissions of HFCS in general should be cut by 80% by 2040. This is important because it will save the planet from 0.5 degrees rise in temperature this century and so works in accordance with the Paris Agreement.

In addition, regulations were put in place, which disallow the sale of HFCs between nations participant to the amendment and those that have yet to sign the legally binding agreement. It also established a fund to aid economically vulnerable nations switch gradually from HFCs to safer alternatives. The Kigali Amendment went into force in the beginning of 2019 on January 1st.

Now, there is also another connection between ozone and climate change.

The ozone layer is mainly concentrated in the upper troposphere and the stratosphere. In the latter, it absorbs solar ultraviolet (UV) rays and so warms up the stratosphere. In the former, it absorbs outgoing infrared radiation. However, because of the huge increase of greenhouse gases which sit directly beneath the ozone layer, infrared radiation no longer reaches the stratosphere, which contributes to cooling.

Additionally, chlorofluorocarbons take a long time to leave the atmosphere and the residual amounts in the air still destroy ozone. This is how this happens. When it gets super cold, the extremely low temperature conditions foster the formation of free chlorine radicals which react freely with the ozone gas. This drastically decreases the amounts of ozone present in the stratosphere. Lower quantities of ozone means a thinner ozone layer and less absorption of UV rays. This in turn leads to cooling of the stratosphere because more heat passes through than would happen normally when the layer is thick.

Also, the oxides of nitrogen (NOx) including nitrous oxide and other types of volatile organic compounds also destroy ozone by reacting with it in a similar manner. These two are naturally produced by events such as volcanic eruptions or through human caused pollution.

In hot seasons, there is less free chlorine and conditions are suitable for the formation of ozone once again. What this means is that the ozone hole grows bigger during winter and smaller in summer.

Generally, lower amounts of ozone means lesser heat absorption in the stratosphere, which is what causes something known as stratospheric cooling. A colder stratosphere causes more ozone destruction and more ozone destruction leads to a further colder stratosphere.

Hydrochlorofluorocarbons (HCFCs) and chlorofluorocarbons (CFCs) were used in insulation, in aerosols, paints, hair products and refrigerants. All these functions were taken up by HFCs which will be further replaced by new alternatives.

The good news is that this opens up the sector to innovation and technology that is both climate and ozone friendly.

So, although these two environmental problems are distinct, they are also interconnected. And solving one helps solve the other.

 

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