Impact on global climate: Greenhouse effect

Question 1

Importance of natural greenhouse effect

Answer 1

Whilst shortwave solar radiation passes through the atmosphere, the Earth’s surface reflects longwave radiation that is readily absorbed by CO2 and CH4, retaining heat close to the Earth’s surface rather than releasing it to space.

This is a natural process and without it, Earth would be 33°C colder! There is a strong correlation between increasing CO2 levels and the rise in global temperatures.

The problem is the enhanced greenhouse effect whereby extra greenhouse gases in the atmosphere are causing radiative forcing.

Question 2

Positive radiative force

Answer 2

The concept of this is that energy is constantly flowing into the atmosphere in the form of sunlight. Some of this sunlight is reflected back to space and the rest is absorbed by the planet. Some of the absorbed energy is radiated back into the much colder surrounding space as infrared energy.

If the balance between the incoming and outgoing energy is anything other than zero, then there has to be some warming (or cooling if the number is negative). Before 1750 radiative forcing was negligible. It has increased because of greenhouse gases and changing albedo because of land use changes