Enhanced greenhouse effect
The enhanced greenhouse effect refers to the increase in the Earth's atmospheric temperature due to human-induced emissions of greenhouse gases (GHGs) such as carbon dioxide (CO2), methane, and nitrous oxide. While a natural greenhouse effect is essential for maintaining life by trapping heat from the Sun, the enhanced version intensifies this process, resulting in anthropogenic climate change. Human activities, particularly the burning of fossil fuels, deforestation, and cement production, have led to rising concentrations of GHGs, significantly impacting global temperatures.
For instance, atmospheric CO2 levels have escalated dramatically in recent decades, with a notable increase from 313 parts per million in 1960 to 418.9 parts per million in 2022. This rise is associated with severe environmental consequences, including increased temperatures, altered precipitation patterns, and phenomena like droughts and desertification. The warming climate also affects the Earth’s albedo effect, as reduced snow cover leads to more solar radiation absorption, further elevating temperatures in a feedback loop. Additionally, the melting of permafrost may release stored methane, compounding the greenhouse gas problem. The ongoing changes underscore the critical relationship between human activity and climate dynamics, highlighting the urgent need for awareness and action.
Enhanced greenhouse effect
Definition
Greenhouse gases (GHGs) in the atmosphere—such as carbon dioxide (CO2), methane, nitrous oxide, water vapor, and ozone—absorb infrared radiation from the Sun and reradiate some of it at the surface, warming Earth’s atmosphere. The average temperature of the atmosphere has been estimated to be more than 30° Celsius warmer than it would be without these gases. The natural greenhouse effect occurs when this process is the result of nonhuman activities; the enhanced greenhouse effect denotes increases in the effect caused by GHGs emitted into the atmosphere by human activities. The enhanced greenhouse effect leads to anthropogenic (human-caused) climate change.
Significance for Climate Change
The concentrations of CO2 and, to a lesser extent, other GHGs have gradually increased in the atmosphere, especially during the twentieth century. For instance, the CO2 content of the atmosphere in the Hawaiian Islands has increased from 313 parts per million in 1960 to 418.9 parts per million in 2022. Arctic ice-core samples indicate that the CO2 content of the atmosphere has also gradually increased over longer timescales. Much of this increase in atmospheric CO2 concentration appears to be due to human activity, although the importance of human activity relative to natural processes such as in volcanism is not clear. It is known, however, that CO2 is released to the atmosphere by human activity, such as the burning of fossil fuels (petroleum, natural gas, and coal). Deforestation of tropical and other forests—such as the Amazon rain forest in Brazil—produces a great deal of CO2 as the plants decay, and it also reduces an extremely important carbon sink, increasing the amount of CO2 that remains in the atmosphere rather than being converted to biomass and oxygen. CO2 is also liberated in cement production.
A continued increase in GHGs will likely cause a continued increase in the average temperature of the atmosphere. The greatest increase in temperature will likely be over polar landmasses. For example, a doubling of the amount of CO2 in the atmosphere has been predicted to cause an average increase of 3° to 4° Celsius at high northern latitudes, resulting in much less snow and ice. Summer conditions might last an extra two months with a correspondingly shorter winter.
Warmer air holds more water vapor than cooler air, so global warming will likely cause the evaporation rate to increase. This increase in evaporation may result in increased drought, desertification, and water shortages in some regions. Although water availability may decrease, greater levels of atmospheric CO2 will mean more CO2 is available to drive photosynthesis, so some plants may benefit from this increase. Warmer temperatures at higher latitudes could also allow some crops such as wheat to be grown further to the north than at the present.
As global temperatures rise, Earth's total area of snow cover is reduced, which in turns affects what is known as the planet's Albedo effect, or the surface of the Earth's ability to reflect solar radiation. Snow inherently reflects solar radiation and therefore leads to a lower degree of absorbed solar radiation throughout snow covered areas. Higher levels of snowfall create areas of higher solar reflectivity, which then leads to a cooling effect as less solar radiation is absorbed by the surface of the Earth. If the Earth's polar caps were to continue to degrade or if snowfall amounts were to lessen, then more solar radiation would be absorbed by the Earth, which would then lead to higher global temperatures and an even further reduction in snow cover. As a result, a worsening Albedo effect could create a feedback loop which would lead to an exponential increase in global warming as snow cover continually reduced. Additionally, melting permafrost is expected to release large amounts of methane gas stored in frozen soil, thus contributing to higher levels of greenhouses gases in the Earth's atmosphere and in turn leading to a further reduction in permafrost.
In 2021, the European Union released a report that revealed ongoing global wildfires had released 1.3 gigatons of carbon dioxide in the month of August alone, the highest value in recorded history. The study concluded that record high temperatures and long dry spells across the globe created the conditions that led to the record spike in global wildfires and that the problem is likely to continue as climate change worsens.
Bibliography
Gray, Ellen. "Unexpected Future Boost of Methane Possible from Arctic Permafrost." NASA, 20 Aug. 2018, climate.nasa.gov/news/2785/unexpected-future-boost-of-methane-possible-from-arctic-permafrost/ Accessed 31 Aug. 2022.
Sharma, Nishant. "Albedo Effect, the Science Behind Climate Change." Medium, 23 Nov. 2020, medium.com/the-green-code/albedo-effect-the-science-behind-climate-change-2f950b027087. Accessed 31 Aug. 2022.
"The Enhanced Greenhouse Effect." Joint Nature Conservation Committee, 4 July 2008, http://jncc.defra.gov.uk/page-4389. Accessed 31 Jan. 2017.
"Trends in Atmospheric Carbon Dioxide." Global Monitoring Laboratory, National Oceanic & Atmospheric Administration, 5 Aug. 2022, gml.noaa.gov/ccgg/trends/. Accessed 31 Aug. 2022.
Watts, Jonathan. "Global Wildfire Carbon Dioxide Emissions at Record High, Data Shows." The Guardian, 21 Sept. 2021, www.theguardian.com/world/2021/sep/21/global-wildfire-carbon-dioxide-emissions-at-record-high-data-shows. Accessed 31 Aug. 2022.
Zillman, John, and Steven Sherwood, reviewers. "The Enhanced Greenhouse Effect." Nova, Australian Academy of Science, 28 Nov. 2016, http://www.nova.org.au/earth-environment/enhanced-greenhouse-effect. Accessed 31 Jan. 2017.