View source for The greenhouse effect and Earth's energy budget

[[Category:Done 2015-06-11]] 
<onlyinclude>The '''greenhouse effect''' plays a significant role in '''Earth's energy budget'''. With the natural [[greenhouse effect]], the [[Earth's energy budget|energy budget]] is balanced as thermal [[radiation]] is re-radiated towards the ground, trapping thermal [[energy]] and warming the Earth. However, with the greenhouse effect being enhanced by humans, the energy budget of the Earth is shifted to an imbalance.</onlyinclude> It is important to understand that a certain amount of energy being retained due to the greenhouse effect is necessary, but too much results in conditions that account for increased [[Temperature of the Earth|global temperatures]] and [[climate change]].<ref name="wolfson">R. Wolfson, (May 8, 2015). Energy, Environment and Climate, 2nd ed. New York, U.S.A.: Norton, 2012.</ref>

==Importance in Energy Budget==
When referring to the Earth's [[climate]], greenhouse effect is the natural heating of a planet's surface from absorption by atmospheric [[greenhouse gases]] such as [[methane]], [[carbon dioxide]], and [[water vapour]].<ref name="wolfson"/>
Without the greenhouse effect, the Earth would not be in an energy balance. Thus to account for this offset, the temperature of the Earth would decrease to a new state of equillibrium. This new temperature, the [[Temperature of the Earth without the greenhouse effect|temperature without the greenhouse effect]], would be far too cold for life as we know it to exist.

[[File:GHGEnergyBudget.png|400px|framed|center|Figure 1. Detailed diagram showing incoming and outgoing energy in a balanced example of Earth's energy budget, with incoming and outgoing values of 341 W/m2. General flows of energy on the surface and in the atmosphere are shown as well, with the area best representing the greenhouse effect located within the dashed box.<ref>''Created internally by a member of the Energy Education team.'' Adapted from: R. Wolfson, Figure 12.5 in ''Energy, Environment and Climate'', 2nd ed. New York, U.S.A.: Norton, 2012, pp. 331</ref>]]

To elaborate on what is happening in Figure 1, we can see that the [[atmosphere]] absorbs a certain amount of radiation that came from the surface of the Earth. Some of this energy passes through the atmosphere but some is absorbed and re-radiated. The greenhouse effect collects and redistributes the energy in this manner by allowing shorter [[wavelength]]s of light to pass through the atmosphere while absorbing longer wavelengths of infrared radiation, later re-radiating that energy back towards the surface. This results in the trapping of longer wavelengths and a higher [[temperature]] on the surface of the Earth.<ref name="RE1">HyperPhysics. (May 1, 2015). ''The Greenhouse Effect'' [Online]. Available: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/grnhse.html</ref>

==Contribution to Warming==
Although the greenhouse effect is necessary in maintaining a temperature on Earth that allows life as we know it to exist, if more greenhouse gases are added into the atmosphere the delicate balance established by the energy budget is disrupted. When more carbon dioxide, for example, is added into the atmosphere, the amount of energy absorbed and then re-emitted by the atmosphere is increased. Since any offset in the energy balance of the Earth must result in a temperature change to account for the difference, the temperature on the Earth increases to create balance once again. Since the addition of carbon dioxide to the atmosphere increases the effect of the greenhouse effect and increases the temperature, the addition is known as a [[climate forcing]] as it destabilizes the Earth's temperature.<ref name="RE2">NASA Earth Observatory. (May 8, 2015). ''Climate and Earth's Energy Budget'' [Online]. Available: http://earthobservatory.nasa.gov/Features/EnergyBalance/page7.php</ref>

The reason that carbon dioxide poses such a risk in terms of upsetting the balance of the Earth's energy budget is because it absorbs a significant amount of thermal energy.<ref name="RE2"/> By adding more carbon dioxide to the atmosphere, the atmosphere becomes more "closed" to energy passing through it, absorbing more. Thus thermal energy that once would have been allowed to escape into space is instead absorbed by carbon dioxide and used to heat the Earth.

The changes in the climate that have occurred so far will continue to happen as the energy imbalance continues to grow with the release of greenhouse gases into the atmosphere. Surface temperatures have risen between 0.6 and 0.9 degrees Celsius, and projections estimate that temperatures will likely rise at least 0.6 degrees in response to the continuing energy imbalance.<ref name="RE2"/> Thus it is important to reduce the emission of greenhouse gases as it will help to reduce this imbalance, ensuring that the only effect that the greenhouse effect has on the energy budget is the one it is intended to have.

==References==
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