As a result of the atmosphere surrounding the Earth trapping some of the incoming solar radiation, the average temperature of the Earth is approximately 15°C. Estimate the amount of radiation that is trapped by the atmosphere, including CO2 and methane, which provides the shield to maintain the temperature at a level that sustains living organisms. Comment on the current concern about global warming as a result of an increasing percentage of CO2 and methane in the atmosphere surrounding the Earth.

Question

GIVEN
The average temperature of the earth is 150C.
FIND
• Amount of radiation trapped by atmosphere
• Comment on concern about global warming as a result of increasing percentage of CO2

Answer 1

Solar radiation flux enters the atmosphere at about 235 W/m2. Out of this about 168 W/m2 reaches the Earth’s surface which is warmed to an average 15°C, while about 67 W/m2 is absorbed by the atmosphere. Steady state is achieved by emission from atmospheric radiation into space at a rate of about 195 W/m2 plus radiation directly from the Earth’s surface at about 40 W/m2.
If the greenhouse gases like CO2 and methane increase in concentration at atmosphere, higher solar radiation flux will be trapped by the gases as a result the steady state atmospheric radiation increases and the temperature of earth increases.
In recent times, due to human activities there is increase in concentration of greenhouse gases like CO2 and methane. This has led to increase in temperature of earth. Polar ice caps are melting gradually which has led to increase in sea level. This phenomenon has threatened lives on earth. If the trend keeps on increasing the earth will be inhabitable to living beings in near future. Thus there is requirement to curb global warming.