CO2 is the chemical formula and a standard symbol for carbon dioxide, a gas that exists in Earth’s atmosphere and which is an important component of various processes, including photosynthesis and ocean-atmosphere exchange. CO2 emission refers to carbon dioxide being expelled as a product or by-product of a process or event and entering the atmosphere.
CO2 emission is the natural result of several different processes and events. It is produced as part of the respiration cycle by living organisms, including both animals and plants. CO2 is also absorbed and released by oceans in the ongoing ocean-atmosphere exchange of CO2. In addition, CO2 emission from within the Earth occurs in small amounts during volcanic eruptions. This collection of natural types of CO2 emission is known as the “carbon cycle.”
There are, however, other types of CO2 emission that have put more carbon dioxide into the atmosphere in recent years than the carbon cycle. Chief among these is combustion of fossil fuels. Fossil fuels include coal, gas, and oil, and their combustion takes place in the running of automobiles, industry, and power plants, for example. Some particular industrial processes involving minerals, metals, and petroleum-based products also result in CO2 emission.
Just as there are natural and human-made sources of CO2 emission, removal of CO2 from the atmosphere occurs through natural and invented processes. Deforestation, partly by reducing carbon sequestration—the process in which trees and plants remove CO2 from the atmosphere—also increases levels of CO2 emission. Geologic sequestration, the collection and storage of CO2emissions in underground reservoirs, is a technique introduced to lesson the impact of processes with heavy CO2 emissions on the amount of CO2 in the atmosphere.
The levels of CO2 in the atmosphere are just part of a wider problem. CO2 is one of the so-called “greenhouse gases” that trap heat in Earth’s atmosphere. Other gases in this category include methane, nitrous oxide, and fluorinated gases. Concerns about climate change are partially focused on the current composition of the atmosphere and the level of greenhouse gases present. This concern takes note of the current level of carbon dioxide, as well as the continued level of CO2 emission from human activity.
Though people disagree about climate change, some steps that individuals can take to cut greenhouse gas emissions, including CO2, are often cost-effective, and may be sensible changes even for people who do not believe that climate change is a problem. Using energy efficient appliances and lightbulbs and having a home energy audit are steps that can reduce greenhouse gas emission at home.