The ozone layer in the upper atmosphere protects humans and other organisms against ultraviolet (UV) radiation from the sun. About 90 per cent of all ozone molecules are found in the stratosphere, a region that begins about 10-16 km above the Earth’s surface and extends up to about 50 km. Most of this ozone is found in the lower stratosphere, commonly known as the “ozone layer.” The remaining 10 per cent of ozone is in the troposphere, the lowest region of the atmosphere.
In the 1970s scientists discovered that certain man-made chemicals deplete the ozone layer, leading to an increased level of UV radiation reaching the Earth. Excessive heat from the sun due to this ozone hole is a major contributor to the high temperature regimes, and the result is global warning.
The United Nations’ (UN) International Day for the Preservation of the Ozone layer is celebrated on September 16. The event commemorates the date of the signing of the Montreal Protocol on Substances that Deplete the Ozone layer in 1987. The 2014 theme of the day is Ozone layer Protection: The Mission Goes on.
Molecules of ozone formed a thin layer in the Earth’s outer atmosphere hundreds of millions of years ago. Ozone depletion substances are chemical compounds that degrade the ozone layer. Since the ozone layer filters the most harmful ultraviolet radiation from the sun before it reaches the land, it is essential to avoid the use of ozone depletion substances in building projects. In the past, these ozone depleting substances like CFCs, HCFCs were used in air-conditioning system as refrigerant. Ozone depletion also occurred due to certain industrially produced chemicals containing chlorine or bromine and damaging the Earth’s protective ozone layer.
Ozone is also produced in the lower atmosphere (troposphere) by the chemical reactions between pollutants like nitrogen oxides and hydrocarbons and UV radiation. This ground-level ozone is a significant component of photochemical smog found in many polluted areas and has adverse effects on human health and environment. For example, increased UV radiation reduces the levels of plankton in the oceans and subsequently diminishes fish stocks. It can also have adverse effects on plant growth, reducing agricultural productivity. Besides, heating, ventilation and air conditioning (HVAC) systems can release compounds into the atmosphere resulting in depletion of the protective ozone layer. With its successful implementation, the Montreal Protocol has been gradually strengthened to cover the phase-out of nearly 100 ozone-depleting substances.
In India, almost 70 per cent of the workforce is dependent on agriculture. The climate change represents an additional stress on ecological and socioeconomic systems that are already facing tremendous pressures due to rapid urbanisation and industrialisation.
A variety of policies and measures have been implemented in reducing the use or emissions of ODSs. India, a party to the Vienna Convention for the Protection of the Ozone layer and the Montreal Protocol on Substances that Deplete the Ozone layer, is one of the countries that have felt the benefit of this work. India’s Central Pollution Control Board (CPCB) has been executing a nation-wide initiative, the National Air Quality Monitoring Programme (NAMP). The annual average concentrations of sulfur oxide levels today are within the prescribed National Ambient Air Quality Standards (NAAQS) in almost all domestic territories.
Most global and regional environmental problems originate in cities, which import increasing amounts of natural resources and export vast quantities of emissions and waste. The main human sources of GHGs contributing to global warming are the dramatic rise in energy use, land-use changes and emissions from industrial activities. There is a need to study the nature of these changes and their ramifications for sustainable human settlement.
Reducing the contribution of cities to climate change, or mitigation, requires an adequate understanding of the drivers of urban GHG emissions, while effective adaptation must be based on a good understanding of what makes cities vulnerable or resilient to climate change impacts. If properly designed, constructed and operated, a sustainable city and sustainable building will require less money and fewer resources to operate and will be healthier for its occupants. Buildings are “sustainable” when they are designed, built and operated with low environmental, social, and economic impacts. Planning looks at the needs of people and the environment while respecting limits to development. Urban planning must recognise regional limits to development to maintain natural habitats and biodiversity.
Use of green areas is a major planning technique by which town planners can prevent or reduce adverse effects of climate. Therefore, many cities in the developed world are planning to transform themselves into green metropolises. The Government of India has prepared a National Action Plan for Climate Change. To address issues relating to mitigation and adaptation in human settlements, a National Mission on Sustainable Habitat has been initiated. It aims to make cities sustainable through improvements in energy efficiency in buildings, management of solid waste and shift to public transport. The National Mission on Sustainable Habitat would broadly cover the following aspects: Extension of the energy conservation building code which addresses the design of new and large commercial buildings to optimise their energy demand; Better urban planning and modal shift to public transport - make long-term transport plans to facilitate growth of medium and small cities in such a way that ensures efficient and convenient public transport; Recycling of material and urban waste management - a special area of focus would be development of technology for producing power form wastes. The mission would also facilitate adaptation to vulnerabilities arising out of climate change like adverse impacts on water resources, increased frequencies of extreme weather like droughts, floods, cyclones, storm water surge, rise in sea levels and heat waves.
Besides, there is a number of practical measures which can be taken at individual level to protect nature Earth. To protect the ozone layer, we must prevent the release of ozone-depleting substances to the atmosphere and select materials with zero ozone depletion potential (ZODP). Whenever possible, we must also replace them with safer alternatives. This significant progress is a useful indicator to protect ozone depletion and boost sustainable development, which would be beneficial for future of planet Earth and mankind.
(Dr Mayarani Ptaharaj teaches at the Department of Architecture, College of Engineering and Technology, Bhubaneswar)