Behind the fight to address global warming and climate change is the rise of greenhouse gases in our atmosphere. A greenhouse gas is any gaseous compound in the atmosphere that is capable of absorbing infrared radiation, trapping and holding heat in the atmosphere. By increasing heat in the atmosphere, greenhouse gases are responsible for the greenhouse effect , which ultimately leads to global warming.
The greenhouse effect occurs because the sun bombards the Earth with enormous amounts of radiation, which hit the Earth’s atmosphere in the form of visible light, in addition to ultraviolet (UV), infrared (IR) and other types of radiation that are invisible to the human eye. About 30% of the radiation that hits Earth is reflected back into space by clouds, ice, and other reflective surfaces. The remaining 70% is absorbed by the oceans, land and atmosphere, according to NASA.
As they absorb radiation and heat up, the oceans, land, and atmosphere release heat in the form of infrared thermal radiation that passes from the atmosphere into space. The balance between incoming radiation and outgoing radiation keeps Earth’s overall average temperature at about 15 degrees Celsius, according to NASA.
This exchange of incoming and outgoing radiation that warms the Earth is known as the greenhouse effect because a greenhouse works in much the same way. Incoming UV radiation easily passes through the glass walls of a greenhouse and is absorbed by plants and hard surfaces inside. However, weaker infrared radiation has difficulty passing through the glass walls and is trapped inside, heating the greenhouse.
How greenhouse gases affect global warming
The gases in the atmosphere that absorb radiation are known as “greenhouse gases” because they are largely responsible for the greenhouse effect. The greenhouse effect, in turn, is one of the main causes of global warming.
The most important greenhouse gases are: water vapor (H2O), carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), according to the Environmental Protection Agency ( EPA).
While some argue that global warming is a natural process and that there have always been greenhouse gases, the amount of gases in the atmosphere has skyrocketed in our recent history. Before the Industrial Revolution, atmospheric CO2 fluctuated between approximately 180 parts per million during the ice ages and 280 parts per million during interglacial warm periods. However, since the Industrial Revolution, the amount of CO2 has increased 100 times faster than the increase when the last ice age ended, according to the National Oceanic and Atmospheric Administration (NOAA).
Fluorinated gases, that is, gases to which the element fluorine has been added, including hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride, are created during industrial processes and are also considered greenhouse gases. Although they are present in very small concentrations, they trap heat very effectively, turning them into gases with a high global warming potential. Chlorofluorocarbons (CFCs), once used as aerosol refrigerants and propellants until they were phased out by international agreement, are also greenhouse gases.
There are three factors that affect the degree to which any greenhouse gas will influence global warming, as follows:
-Its abundance in the environment.
-How long it remains in the environment.
-Its global warming potential.
Carbon dioxide has a significant impact on global warming, in part due to its abundance in the atmosphere. However, methane is about 21 times more efficient at absorbing radiation than CO2, giving it a higher GWP (Global-warming potential ) rating, even though it remains in the atmosphere for only about 10 years, according to the EPA.
Some greenhouse gases, such as methane, are produced through agricultural practices, including livestock manure. Others, such as CO2, are largely the result of natural processes such as respiration and the burning of fossil fuels such as coal, oil, and gas.
The second cause of CO2 release is deforestation. When trees are cut down to produce goods or heat, they release carbon that is normally stored for photosynthesis. This process releases nearly 1 billion tons of carbon into the atmosphere per year, according to the 2010 Global Forest Resources Assessment.
The future
If current trends continue, scientists, government officials and a growing number of citizens fear that the worst effects of global warming (extreme weather, rising sea levels, extinctions of plants and animals, acidification of the oceans, major changes in unprecedented weather and social upheaval) are inevitable.
Reference: NASA and EPA (Enviromental Protection Agency)
