U.S. Energy Information Administration - EIA - Independent Statistics and Analysis
Frequently Asked Questions
What are greenhouse gases and how do they affect the climate?
The major greenhouse gases that the United States emitted as a result of human activity in 20121 (and their share of total emissions) were2
- Carbon dioxide (83%)
- Methane (9%)
- Nitrous oxide (6%)
- Hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (collectively 3%)
There are other greenhouse gases that are not counted in U.S. or international greenhouse gas inventories:
- Water vapor -- the most abundant greenhouse gas. Most scientists believe that water vapor produced directly by human activity contributes very little to the amount of water vapor in the atmosphere. Therefore, EIA does not estimate emissions of water vapor. Research by NASAsuggests a stronger impact from the indirect human effects on water vapor concentrations in the atmosphere.
- Ozone -- technically a greenhouse gas because it has an effect on global temperature. However, at higher elevations in the atmosphere (stratosphere), where it occurs naturally, it is needed to block harmful UV light. At lower elevations of the atmosphere (troposphere) it is harmful to human health and is a pollutant regulated independently of its warming effects.
Greenhouse gases are transparent to incoming (short-wave) radiation from the sun but block infrared (long-wave) radiation from leaving the Earth's atmosphere. This greenhouse effect traps radiation from the sun and warms the planet's surface. As concentrations of these gases increase, more warming occurs than would happen naturally.
Most recent monthly and annual estimates for U.S. Carbon Dioxide Emissions From Energy Consumption.
Emissions of Greenhouse Gases in the United States, 2009, EIA's last annual report on total U.S. greenhouse gas emissions.
Last updated: June 27, 2014
Other FAQs about Environment
- Does EIA have projections for energy production, consumption, and prices for individual states?
- How do I convert between short tons and metric tons?
- How does the hole in the ozone layer affect global warming?
- How much carbon dioxide is produced by burning gasoline and diesel fuel?
- How much carbon dioxide is produced per kilowatthour when generating electricity with fossil fuels?
- How much carbon dioxide is produced when different fuels are burned?
- Why do carbon dioxide emissions weigh more than the original fuel?
- How much of U.S. carbon dioxide emissions are associated with electricity generation?
- What are greenhouse gases and how do they affect the climate?
- What are the energy-related carbon dioxide emissions by source and sector for the United States?
- What are the greenhouse gas and air pollutant emissions factors for fuels and electricity?
- What are the sources of energy-related carbon dioxide emissions by type of fuel for the United States and the world?