Human activities modified the atmospheric energy flow

The causes of Greenhouse Effect

I. Greenhouse gases (Sources: Integrated Approach, Nelson, P. 236)

• Carbon dioxide --- burning of fossil fuels from powerhouses, factories and vehicles, and burning forests
• Nitrous oxide --- vehicle exhausts, fertilizer, and power stations.
• CFCs --- refrigerators, solvents and foams

II. How do the greenhouse gases affect the global temperature?

• Greenhouses gases increase insolation received by the earth.
• Carbon dioxide and nitrous oxide trap some of outgoing radiation.
• Less heat escapes into space.
• The earth-atmosphere will become warmer and warmer.
• It is found that the earth’s temperature increases 0.5℃ from 19^th to 20^th century.
• The breaking down of the ozone layer with emission of CFCs allows the incoming of more ultraviolet energy.

III. The earth becomes hotter and hotter. Is it True?

Burning of fossil fuels

® more CO₂ is released.

®increased turbidity of air

®the incoming radiation is blocked and scattered.

®increased albedo due to deforestation and overgrazing

®increased dust particles of air as condensation nuclei in the atmosphere

®It promotes condensation and cloud formation which reflect or scatter incoming radiation

The atmosphere becomes cooler and cooler.

By Suen Hoi Wing