Question

Where do greenhouse gases come from?

Answer 1

Natural and human made sources.

Explanation:

The main natural greenhouse gases are CO2, CH4 (methane) and N2O (nitrous oxide). Volcanoes and forest fires emit large volumes of CO2, while rotting vegetation can release large amounts of methane gas. Nitrous oxide emissions occur naturally through many sources associated with the nitrogen cycle, which is the natural circulation of nitrogen among the atmosphere, plants, animals, and microorganisms that live in soil and water (http://www3.epa.gov/climatechange/ghgemissions/gases/n2o.html)

However, human activities that burn fossil fuels and burning forests cause even more of these main greenhouse gases to pile up in the atmosphere. CO2 sources include coal-fired power plants, refineries, oilsands plants, cement plants and millions of cars, trucks and planes. Human sources of methane include leaking natural gas pipelines and rice paddies.

Humans have also put "new greenhouse gases" into the atmosphere, that never existed before, like CFCs and HCFCs and SF6. Also, these greenhouse gases of have different Global Warming Potential (see graph). If CO2 has a warming potential of 1, for example methane is about 25X more powerful and SF6 is nearly 23,000X more powerful than CO2!