Global warming is the increase average temperature of the Earth's near-surface air and oceans:

• Most prominent factor is from the combustion of fossil fuels in cars, factories and electricity production. They produce carbon dioxide, which is the most common gas responsible for the global warming.
• Other contributors include methane released from landfills and fertilizers.
• Gases used for refrigeration and industrial processes.
• The loss of forests that would otherwise store CO2.