What is greenhouse gases’ impact on global warming?
The increase in greenhouse gases in our atmosphere is at the root of the phenomena of global warming and climate change. A greenhouse gas is any gaseous compound in the atmosphere that absorbs infrared radiation, trapping and holding heat in the atmosphere. Greenhouse gases causes the greenhouse effect by increasing the heat in the atmosphere, which eventually leads to global warming. (The effects of global warming can be seen all over the world.)
The “Greenhouse Effect” and Solar Radiation
Global warming is not a new scientific theory. Svante Arrhenius, a Swedish physicist and chemist, discovered the fundamentals of the phenomenon in 1896. His paper, published in the Philosophical Magazine and the Journal of Science, was the first to quantify carbon dioxide’s contribution to what scientists now refer to as the “greenhouse effect.”
The greenhouse effect occurs because the sun bombards Earth with massive amounts of radiation, which strike the Earth’s atmosphere as visible light, ultraviolet (UV), infrared (IR), and other types of radiation that are invisible to the human eye. UV radiation is shorter in wavelength and has a higher energy level than visible light, whereas IR radiation is longer in wavelength and has a lower energy level. Clouds, ice, and other reflective surfaces reflect approximately 30% of the radiation that strikes Earth back into space. According to NASA’s Earth Observatory, the remaining 70% is absorbed by the oceans, land, and atmosphere.
As they heat up, the oceans, land, and atmosphere emit heat in the form of infrared thermal radiation, which escapes into space. According to NASA, it is the balance of incoming and outgoing radiation that allows the Earth to be habitable, with an average temperature of about 59 degrees Fahrenheit (15 degrees Celsius). Without this atmospheric balance, Earth would be as lifeless and cold as its moon, or as scorching hot as Venus. The dark side of the moon, which has almost no atmosphere, is about minus 243 F (minus 153 C). Venus, on the other hand, has a dense atmosphere that traps solar radiation; the average temperature on Venus is approximately 864 degrees Fahrenheit (462 C).
Because an agricultural greenhouse works in much the same way, the exchange of incoming and outgoing radiation that warms the Earth is commonly referred to as the greenhouse effect. Incoming shortwave UV radiation easily passes through a greenhouse’s glass walls and is absorbed by the plants and hard surfaces within. Longwave infrared radiation, on the other hand, has difficulty passing through the glass walls and is thus trapped inside, warming the greenhouse.
How Greenhouse Gases Cause Global Warming?
Because they are largely responsible for the greenhouse effect, the gases in the atmosphere that absorb radiation are known as “greenhouse gases” (abbreviated as GHG). In turn, the greenhouse effect is one of the primary causes of global warming. According to the Environmental Protection Agency (EPA), the most significant greenhouse gases are water vapor (H2O), carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O).
While oxygen (O2) is the second most abundant gas in our atmosphere, it does not absorb thermal infrared radiation, according to Michael Daley, an associate professor of environmental science at Lasell College in Massachusetts.
Global warming and the greenhouse gases that cause it occur naturally; without them, the average surface temperature of the Earth would be a chilly zero degrees Fahrenheit (minus 18 C). However, the amount of greenhouse gases in the atmosphere has recently skyrocketed to dangerous levels.
During the 20,000-year period preceding the Industrial Revolution, atmospheric CO2 levels fluctuated between 180 and 280 parts per million (ppm) during ice ages. According to NASA’s Global Climate Change portal, CO2 levels have risen nearly 50% since the start of the Industrial Revolution in the 1750s. CO2 levels are now above 410 ppm.
Fluorinated gases, which are gases that have had the element fluorine added to them, are produced during industrial processes and are also classified as greenhouse gases. Hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride are examples of these. Although they are present in very low concentrations in the atmosphere, they trap heat very effectively, making them high “global warming potential” (GWP) gases.
CFCs, which were once used as refrigerants and aerosol propellants before being phased out by international agreement, are also greenhouse gases.
There are three factors that influence how much a greenhouse gas contributes to global warming: Its abundance in the atmosphere, the length of time it remains in the atmosphere, and its GWP. According to NASA, water vapor is the most abundant greenhouse gas, but carbon dioxide has a greater impact on global warming due to its abundance in the atmosphere and relatively long atmospheric lifetime of 300 to 1,000 years. According to a 2020 study published in the Journal of the Atmospheric Sciences, water vapor has an atmospheric lifetime of no more than 10 days.
According to the United Nations Framework Convention on Climate Change (UNFCCC), methane is about 21 times more efficient at absorbing radiation than CO2, giving it a higher GWP rating despite remaining in the atmosphere for only about 12 years. Despite the fact that methane and other GHGs can trap more heat than CO2, scientists still consider carbon dioxide to be the dominant greenhouse gas because its warming effect outlasts the others by centuries.
Greenhouse Gases Sources
Some greenhouse gases, such as methane, are produced by agricultural practices, such as livestock manure. Others, such as CO2, are primarily the result of natural processes such as respiration as well as the combustion of fossil fuels such as coal, oil, and gas.
Deforestation is another major source of CO2. When trees are cut down to make goods or heat, the carbon that is normally stored for photosynthesis is released. According to the World Resources Institute, this process emits up to 4.8 billion metric tons of carbon into the atmosphere each year.
Some of these greenhouse gas emissions can be offset by forestry and other land-use practices. “Replanting helps to reduce carbon dioxide buildup in the atmosphere because growing trees sequester carbon dioxide through photosynthesis,” Daley explained. “However, forests cannot sequester all of the carbon dioxide we emit to the atmosphere through the combustion of fossil fuels, and a reduction in fossil fuel emissions is still required to avoid atmospheric buildup.”
The production of greenhouse gases is a major source of concern around the world. According to NOAA’s Climate.gov, atmospheric CO2 has increased at a rate 100 times faster than previous natural increases over the last 60 years. The last time global atmospheric CO2 levels were this high was 3 million years ago, when temperatures were up to 5.4 degrees Fahrenheit (3 degrees Celsius) above pre-industrial levels. As a result of modern-day CO2-induced global warming, 2016 was the warmest year on record, with 2019 and 2020 following suit. According to the World Meteorological Organization, the six hottest years on record have all occurred since 2015.
“The warming we’re seeing affects atmospheric circulation, which affects rainfall patterns all over the world,” said Josef Werne, an associate professor in the University of Pittsburgh’s Department of Geology and Planetary Science. “This will result in significant environmental changes and challenges for people all over the world.”
The Future of Our Planet
Scientists, government officials, and an increasing number of citizens fear that if current trends continue, the worst effects of global warming — extreme weather, rising sea levels, plant and animal extinctions, ocean acidification, major shifts in climate, and unprecedented social upheaval — will be unavoidable.
In order to combat GHG-induced global warming, the United States government developed a climate action plan in 2013. According to the UNFCCC, representatives from 73 countries signed the Paris Agreement in April 2016, an international pact to combat climate change by investing in a sustainable, low-carbon future. Despite withdrawing from the Paris Agreement in 2017, the United States will re-join in late January 2021. The administration of President Biden has also set a target of reducing US emissions by 50-52% from 2005 levels by 2030. (Emissions are frequently compared to those in 2005, when CO2 emissions in the United States peaked at nearly 6 billion tons.)
According to Nature, global carbon dioxide emissions fell 6.4% (13% in the United States alone) in 2020, marking the first time in decades that the annual rate has not risen (opens in new tab). This was due in part to a decrease in fossil fuel combustion as a result of the switch from coal to natural gas, but it was also due to the forced halt in economic, social, and transportation activities as a result of the COVID-19 pandemic. Scientists expected the annual emissions decline to be greater, but emissions rebounded as restrictions were lifted in some countries and activity recovered toward the end of 2020.
According to the UN Environment Programme, the world still needs to cut CO2 emissions by 7.6% over the next decade in order to limit global warming to the 2.7 degree F (1.5 degree C) target set by the Paris Agreement.
Researchers all over the world are working to reduce greenhouse gas emissions and mitigate their effects. One potential solution that scientists are investigating is sucking some of the carbon dioxide from the atmosphere and burying it indefinitely underground. Carbon capture and storage, proponents argue, is technologically feasible, but market forces have prevented widespread adoption.
Whether or not it is possible to remove already-emitted carbon from the atmosphere, preventing future warming requires a reduction in greenhouse gas emissions. The 2016 Paris Agreement is the most ambitious effort to date to prevent global warming. According to the United Nations, this nonbinding international treaty aims to keep warming “well below 2 degrees Celsius above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5 degrees Celsius.” Each treaty signatory agreed to set their own voluntary greenhouse gas emission limits and to tighten them over time. Climate scientists said the agreement’s emissions limits would not keep warming to 1.5 or even 2 degrees Celsius, but they would be an improvement over the “business-as-usual” scenario.