Unit: 2

Carbon Dioxide

Carbon dioxide (CO2) is one of the main greenhouse gases that trap heat in the Earth's atmosphere, causing the planet to warm. The burning of fossil fuels, deforestation and land-use change, are the primary sources of increased CO2 in the atmosphere.

CO2 is considered to be the most important greenhouse gas in terms of its contribution to human-induced climate change. This is because it is released in large quantities from the burning of fossil fuels, and it stays in the atmosphere for a long period of time (hundreds to thousands of years). The concentration of CO2 in the atmosphere has been rising rapidly in the past century and has now reached levels not seen for at least 800,000 years. The burning of fossil fuels is the largest source of CO2 emissions, accounting for about 78% of total greenhouse gas emissions.

The warming caused by the increased levels of CO2 and other greenhouse gases in the atmosphere is causing a number of changes to the Earth's climate, including rising sea levels, more extreme weather events, and changes in the distribution of plants and animals. Scientists have found a strong correlation between the increase in CO2 concentrations and the warming of the Earth's surface. Reducing CO2 emissions is essential to slow down the rate of climate change and to mitigate its impacts.

Methane & Climate Change 

Methane is a potent greenhouse gas, which means it has a warming effect on the Earth's climate. It is estimated to be 28-36 times more effective at trapping heat in the atmosphere than carbon dioxide over a 100-year timescale. Methane is released into the atmosphere through a variety of human activities such as the extraction and transport of fossil fuels, livestock farming, and the decomposition of waste in landfills

It is also released naturally through processes such as volcanic activity and the decay of organic matter in wetlands. Reducing methane emissions is considered an important strategy for slowing the rate of climate change.

Nitrous oxide & climate change  

Nitrous oxide (N2O) is a greenhouse gas that contributes to climate change. It is released into the atmosphere through various human activities, such as agriculture (from the use of fertilizers), industrial processes, and burning fossil fuels. Nitrous oxide is also released naturally by oceans and soils. Nitrous oxide is a powerful greenhouse gas, with a global warming potential 298 times greater than carbon dioxide over a 100-year period. Thus, controlling emissions of nitrous oxide is important for mitigating climate change.

CFCs & climate change 

Chlorofluorocarbons (CFCs) are a group of man-made chemicals that were widely used in the 20th century as refrigerants, solvents, and propellants in aerosol cans. CFCs are also greenhouse gases, and their emissions contribute to climate change.

When CFCs are released into the atmosphere, they rise into the stratosphere, where they come into contact with UV radiation. This causes the CFC molecules to break down, releasing chlorine atoms that deplete the ozone layer. The depletion of the ozone layer allows more UV radiation to reach the Earth's surface, which can increase the risk of skin cancer, cataracts, and other health problems.

In 1987, the Montreal Protocol was adopted to phase out the production and consumption of CFCs and other ozone-depleting substances. Since then, the ozone layer has started to recover and the hole in the ozone layer over Antarctica has started to shrink. Although the production and consumption of CFCs have been phased out, CFCs that have already been released into the atmosphere will continue to deplete the ozone layer for decades to come and also contribute to the climate change.