JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III Year FUNDAMENTALS OF MECHANICAL ENGINEERING Previous Question Paper (August - 2022 - R16)

• Global Warming refers to the long-term increase in the Earth's average surface temperature due to the Greenhouse Effect. It is primarily caused by the accumulation of greenhouse gases (GHGs) like carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) in the atmosphere, which trap infrared radiation emitted by the Earth.
• Ozone Depletion refers to the thinning of the Ozone Layer in the stratosphere (specifically the ozone hole over Antarctica). This is primarily caused by the release of Chlorofluorocarbons (CFCs) and other ozone-depleting substances (ODS), which release chlorine and bromine atoms that catalyze the destruction of ozone molecules (O3).
• The primary difference lies in the mechanism and impact: Global warming alters the Earth's heat balance, leading to climate change, while ozone depletion reduces the atmosphere's ability to filter harmful ultraviolet (UV-B) radiation, increasing the risk of skin cancer and cataracts.

The relationship between global warming and ozone depletion is complex and often counterintuitive due to the different layers of the atmosphere involved:

• Stratospheric Cooling: While greenhouse gases trap heat in the lower atmosphere (troposphere), they actually lead to a cooling effect in the upper atmosphere (stratosphere). This occurs because GHGs radiate heat out into space from the stratosphere.
• Impact on Ozone Chemistry: The chemical reactions that destroy ozone are temperature-dependent. Lower temperatures in the stratosphere promote the formation of Polar Stratospheric Clouds (PSCs). These clouds provide a surface for chemical reactions that convert inactive chlorine into highly reactive forms that rapidly destroy ozone.
• Feedback Loop: Consequently, as global warming increases the concentration of greenhouse gases, it inadvertently accelerates the cooling of the stratosphere, which in turn facilitates the conditions necessary for ozone depletion to persist, even as CFC emissions are reduced.
• In summary, global warming acts as a catalyst that can exacerbate the severity and duration of ozone depletion in the polar regions.