Greenhouse Effect and Greenhouse Gases
The greenhouse effect is caused by the gases present in the atmosphere. Here is a step-by-step description of what happens.
- The energy from the sun passes through the atmosphere reaching the Earth’s surface.
- Part of the energy is absorbed by the Earth, while the rest is reflected back.
- Most of the reflected energy (93%) does not pass back through the atmosphere, but gets trapped in it, because the sun and the earth emit energy as different forms of radiation.
The sun emits mainly visible and ultraviolet radiation, while the Earth emits mostly infrared. The atmosphere is transparent to visible/ultraviolet radiation, but absorbs the infrared. Therefore, most of the heat from the earth stays caught inside the atmosphere. The gases causing this phenomenon are called greenhouse gases, mainly natural ones, water and CO2.
The greenhouse effect is essential for life on our planet. Earth’s surface temperature would be much lower – about -18oC instead of +15oC – if the atmosphere didn’t hold energy – too cold for humans, as well as many other animal species and vegetation.
There has been a lot of concern in recent years over the emission of other greenhouse gases, such as methane, nitrous oxide and CFCs. Furthermore, there has been an increase in the concentration of CO2, all due to human activity.
As a consequence of the increase in the greenhouse effect, more heat gets absorbed by the atmosphere. According to the Intergovernmental Panel on Climate Change, this may be the cause of increases in the Earth’s temperature (global warming), although not everyone agrees with this theory.
Greenhouse Effect and Ozone Depletion: Almost Nothing in Common
CFCs are responsible for ozone layer depletion, as they react with ozone, and are also greenhouse gases because they absorb the heat emitted from the earth. This responsibility is the only thing these two issues have in common – they are very different phenomena, based on different principles. Some conclusive points to remember:
- The greenhouse effect and ozone layer depletion are two independent phenomena. They do not influence or affect one another.
- Ozone layer depletion does not cause the greenhouse effect. It allows more ultraviolet energy to reach the Earth’s surface, but it does not affect the absorption of heat inside the atmosphere.
- Ozone layer depletion cannot cause any increase in the Earth’s temperature.
- CO2, which is the main greenhouse gas, whose concentration in the atmosphere is increasing due to human activity, does not cause any depletion of the ozone layer.
As you can see, CFCs are the cause (or part of the cause) for both the global warming potentially arising from an increase in the greenhouse effect and the depletion of the ozone layer – but that’s the only thing the two phenomena have in common.
Dim Coumou, et al. Global warming has increased monthly heat records by a factor of five. (2013). Potsdam Institute for Climate Impact Research. Accessed January 15, 2013.
United Nations Environment Programme. The Ozone Secretariat. (2013). Accessed January 15, 2013.
NASA. 2012 Antarctic Ozone Hole Second Smallest in 20 Years. (2012). Accessed January 15, 2013.
Glen P. Peters, Robbie M. Andrew, Tom Boden, Josep G. Canadell, Philippe Ciais, Corinne Le Quéré, Gregg Marland, Michael R. Raupach & Charlie Wilson. The challenge to keep global warming below 2 °C. (2012). Nature Climate Change. Accessed January 15, 2013.
Hocking M.B., Handbook of Chemical Technology and Pollution Control, Third Edition. (2005. Elsevier.
The National Academics. Understanding and Responding to Climate Change. (2008). Accessed January 15, 2013.
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