Role of Co2 As a Greenhouse Gas

As a greenhouse gas, carbon dioxide (CO2) is a known contributor to global temperature rise. Activists, policy makers, and other parties interested in lowering greenhouse gas emissions often target CO2 as one of the most prevalent and hazardous forms of air pollution. This is, at least in part, because CO2 is a frequent byproduct of internal combustion machines and activities common to industrialized society.

Sources

• Carbon dioxide is created during aerobic respiration and the burning of carbon-based fuels. When animals, including humans, breathe in oxygen, they exhale carbon dioxide. When wood and fossil fuels (such as oil and coal, which are made of decomposed and compressed carbon-based life forms) burn, the carbon in the fuel is released into the atmosphere as carbon dioxide. According to the "Emissions of Greenhouse Gases Report" published by the U.S. Energy Information Administration, "Energy-related carbon dioxide emissions account for 98 percent of U.S. carbon dioxide emissions." Common sources of carbon dioxide include automobiles, electricity plants, planes and factories.

Greenhouse Gases

• CO2 and other greenhouse gases trap heat in the form of infrared radiation, a type of radiation given off by the sun. Greenhouse gases prevent this radiation from leaving the atmosphere, acting as a blanket around the Earth. As more heat is trapped on Earth, temperatures climb. This creates a "greenhouse effect," which becomes cumulative as more heat enters the system.

How It Works

• A carbon dioxide molecule is made of two oxygen atoms that have bonded to a carbon atom. Due to the structure of these atoms, bonds between carbon and oxygen are particularly flexible and strong. When infrared radiation tries to leave the Earth's atmosphere, it hits the bonds, which bounce the radiation back to Earth--essentially trapping the radiation in Earth's atmosphere.

Amount

• The National Oceanic and Atmospheric Administration has found more than 380 parts per million (ppm) of CO2 in the atmosphere. Compared to approximately 337 ppm in 1978, this number shows a dramatic increase in carbon dioxide in a little more than 30 years. It vastly outstrips the amount of nitrous oxide and methane, the next two most abundant man-made greenhouse gases. It also exceeds the limit of 350 ppm that NASA scientist James Hansen says is the maximum amount of CO2 the Earth can sustain without massive climate change.

Impact

• The more CO2 there is in the atmosphere, the more heat it traps. Unfortunately, many areas vulnerable to temperature change are also vital for sustaining biodiversity. For example, estuaries are crucial as hatcheries for many fish species and are sensitive to both temperature and sea level rise that results from polar ice caps melting. Thus, as temperatures rise, species that depend on estuaries to nurture their young are in danger of dying out. The impact of CO2 on this process lies not in the structure of the molecule or its properties but in its abundance.