(a) State three ways in which human activities affect the composition of the atmosphere (b) Describe the physical changes that are likely to be associated w...

(a) Three ways human activities affect the composition of the atmosphere

• Burning of fossil fuels in industries, power stations and vehicles releases carbon dioxide, carbon monoxide and sulphur oxides, raising the level of these gases.
• Deforestation and bush burning reduce the trees that absorb carbon dioxide and add smoke and carbon dioxide, so the proportion of carbon dioxide rises while oxygen falls.
• Release of chlorofluorocarbons (CFCs) from aerosols, refrigerators and air-conditioners adds ozone-destroying gases to the atmosphere; industrial gases and dust also add particles and pollutants.

(b) Physical changes associated with the increasing reduction of the ozone layer

The ozone layer in the stratosphere shields the earth by absorbing harmful ultra-violet (UV) radiation from the sun. Its thinning lets more UV reach the surface, so the likely physical changes are:

• A general rise in surface temperature and reinforcement of global warming.
• Melting of ice caps and glaciers, leading to a rise in sea level and flooding of low-lying coasts.
• Increased UV radiation reaching the ground, which harms plants, reduces crop yields and damages marine life such as plankton.
• Changes in weather and rainfall patterns, with more droughts in some areas and heavier rain or storms in others.
• Increased human and animal health hazards such as skin cancer, cataracts and weakened immunity (a consequence of the increased UV).