Which Gases Are the Primary Drivers of the Greenhouse Effect?
Certain natural and human-generated substances in the atmosphere capture heat, keeping the planet warm enough for life. An excess of these substances can raise global temperatures, a phenomenon referred to as the greenhouse effect.
By Finley Davis
Burning fossil fuel such as coal produces carbon dioxide, a greenhouse gas.
Compounds that capture heat in the Earth's atmosphere, both naturally occurring and human-made, maintain temperatures suitable for plants and animals. If these gases accumulate excessively in the atmosphere, global temperatures may rise, a process called the greenhouse effect.
Carbon Dioxide
The Environmental Protection Agency (EPA) notes that carbon dioxide (CO2) is released through the natural carbon cycle and human actions like the combustion of fossil fuels. Typically, oceans and plants absorb CO2 emitted into the atmosphere in roughly equal quantities. Yet, since the 1700s, human emissions have outpaced natural removal. By 2005, atmospheric carbon dioxide levels were approximately 35 percent higher than before the Industrial Revolution, contributing to an increase in average global temperatures.
Methane
Methane (CH4) is a primary component of natural gas and a greenhouse gas that influences climate. According to the US Climate Change Science Program (CCSP), methane traps heat 20 times more effectively than carbon dioxide. Since methane persists for 9 to 15 years, cutting methane emissions could aid in reducing global warming relatively quickly. Human activities such as landfills, agriculture, and coal mining account for about 60 percent of global methane emissions.
Nitrous Oxide
Commonly known as "laughing gas" for its use in dental sedation, nitrous oxide also harms the ozone layer. In the stratosphere, ozone blocks harmful ultraviolet rays. Research from the National Atmospheric and Oceanic Administration suggests that by the end of the 21st century, ozone levels will be 4 percent lower than pre-Industrial Revolution levels due to nitrous oxide emissions. Lowering these emissions is difficult because nitrous oxide is a natural byproduct of agriculture: nitrogen fertilizers in soil stimulate bacteria that produce it.
Fluorocarbons
Fluorocarbons are synthetic substances that have contributed to ozone depletion. They were historically used in refrigerants, chemical solvents, and insulating foams. The resulting damage to the ozone layer permits ultraviolet (UV) rays to reach the Earth's surface. The EPA indicates that overexposure to UV can lead to cataracts and cancer, and it also affects crop yields and disrupts the marine food chain. In late 1978, the U.S. prohibited chlorofluorocarbons (CFCs) in spray propellants. Since 1987, nearly 200 countries have agreed to phase out CFCs and other ozone-depleting substances. Nevertheless, these chemicals are still manufactured for essential purposes, such as metered-dose inhalers for asthma patients.
