ओजोन क्षयकारी पदार्थ और जलवायु परिवर्तन

To combat the threat posed by ozone-depleting substances, the world adopted the Montreal Protocol in 1987, limiting the production and consumption of these compounds. This treaty has helped reduce global ozone depletion to a great extent, with over 98 percent of the world’s consumption of these chemicals now phased out.

Chlorofluorocarbons (CFCs)

Chlorofluorocarbon (CFC) is a synthetic chemical with a high global warming potential and is commonly used in air conditioning systems. It can last for 52 years in the atmosphere. Even though efforts have been made to reduce its usage, the continued use of CFCs threatens the ozone layer. 

CFCs are non-toxic, but they deplete the ozone layer. This layer is a belt of ozone molecules in the stratosphere, and it protects our planet by absorbing most of the sun’s ultraviolet radiation. Researchers studied the chemical reactions associated with CFC breakdown in the stratosphere. They found that the chemical reactions that follow the breakdown of the ozone layer make CFCs harmful to life on Earth.

In the 1970s, CFCs were commonly used in everyday household products, and they depleted the ozone layer, allowing ultraviolet radiation to reach the Earth’s surface. The US government advocated for solid controls, international cooperation, and consensus to phase out the chemicals in the atmosphere. The United States ratified the treaty unanimously in 1988, and the protocol has received bipartisan support for thirty years.

But recent estimates have shown that CFC banks contain significantly more chemicals than previously thought. One study estimated that unchecked CFC-11 and CFC-12 emissions could delay the ozone layer’s recovery. That is the equivalent of nine billion metric tons of carbon dioxide, which is equal to the commitments made by the European Union under the UN Paris Agreement.

The Montreal Protocol helped implement the ban on CFCs and is an excellent example of the power of multilateral initiatives. Currently, 197 countries have ratified the Montreal Protocol, enforcing its prohibition on CFCs. It is encouraging to note that the compliance rate of the Montreal Protocol signatory states is 98%, and many have met their targets ahead of schedule. The atmospheric levels of essential ozone-depleting substances are declining, and global observations show that they will return to their pre-1980 levels by the end of the century.

To understand the effects of these ozone-depleting substances, we need to know how they deplete the ozone layer. As a result of the destruction of stratospheric ozone, more harmful UV-B radiation reaches Earth’s surface. CFCs break down ozone in catalytic reactions, and each chlorine atom destroys approximately 100,000 molecules of ozone.

Hydrofluorocarbons (HFCs)

Although the process of limiting the use of CFCs in the atmosphere is still ongoing, it has been an effective way to determine their harmful effects. The Montreal Protocol requires that industries reduce the amount of HFCs and other ozone-depleting substances that contribute to global warming. The agreement is a living document that is regularly amended and adjusted to reflect current scientific knowledge. While regulating CFC levels is essential, it’s not enough to cut down on all HFC emissions.

The Kigali Amendment of the Montreal Protocol, signed in 2007, requires that all nations drastically reduce the amount of ozone-depleting substances in the atmosphere. While this is an essential step toward a sustainable climate, full ozone layer recovery will take decades. But the progress so far has been encouraging. As the Kigali Amendment has reduced HFC emissions in developed countries, it is time for developing countries to follow suit.

The Kigali Amendment requires that the EPA issue allowances for producers to reduce the use of HFCs. The EPA proposed to issue the first set of budgets for 2022 on October 1, 2021, and EPA says the rulemaking is on track to issue the first allocations by October 1, 2021. The EPA is also on track to issue 2022 allowances, as requested by a state and local government coalition.

A global overview of the emission of HFCs is needed to assess the impact of this substance on climate change. The problem is that the global estimates of HFC emissions are inconsistent and often inaccurate, with data from one-off atmospheric studies providing estimates only for a few years. Bottom-up studies are more comprehensive but lack the same data quality and rarely quantify uncertainties. It is also essential to consider the spatial resolution of emission estimates to compare global and regional emissions. The latter can help evaluate policy tools and controls, while country-level emission estimates can allow for a worldwide comparison of HFC emissions.

The use of HFCs is widespread. The EPA estimates that in 2010, the industry used 38 million metric tons of HFCs to create closed-cell thermal insulation materials. Approximately 98% of this total HFC use is in developed countries. In 2010, HFCs were responsible for about a third of the total carbon dioxide equivalent emissions. This amount equals about eight and a half million average gasoline passenger cars driving 11,500 miles per year.