The greenhouse effect

CO2 and several other gases in the Earth’s atmosphere help trap heat, as in a greenhouse – hence the term greenhouse gases.

The build-up of greenhouse gases in the atmosphere causes more heat to be retained, which leads to global warming and other climate change impacts. CO2 is of particular concern because it is the most abundant man-made greenhouse gas.

Human activity and climate change

Burning fossil fuels releases CO2 into the atmosphere. Since the Industrial Revolution in the 1800s, the world’s population has grown tremendously, as has the use of coal, oil, and natural gas to power modern societies.  

As more fossil fuels are burned, the concentration of CO2 in the atmosphere rises, and more heat is trapped through the greenhouse effect. Although many factors have an impact on the climate, most scientists agree that the current rise in average global temperatures is due to our extensive use of fossil fuels.

• Average CO2 concentrations in the atmosphere, which were approximately 280 parts per million (ppm) in pre-industrial times, have risen to approximately 390 ppm in 2010

• The Earth’s surface is currently warming at a rate of about 3°F per century; the eight warmest years on record (since 1880) have all occurred since 2001, with the warmest year being 2005

• Although CO2 concentrations have fluctuated naturally throughout Earth’s history, they have never risen so much in such a short time as today

EPA’s regulation of greenhouse gases

The U.S. Environmental Protection Agency (EPA) has classified greenhouse gases as air pollutants. This finding allows EPA to regulate emissions of greenhouse gases to protect human health and welfare, which may be adversely affected by global warming.