Most of the greenhouse gas emitted through human activity comes from the production of energy.

This group of gases is thought to contribute to global climate change, long-term shifts in weather partly due to the tendency of these gases to trap energy, in the form of electromagnetic radiation from the sun, that would otherwise have been reflected back out into space. For more about the relationship between the climate and greenhouse gases, go here.

Noteworthy greenhouse gases  are carbon dioxide, nitrous oxide, methane, hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6).

Energy creation results in such a high level of greenhouse gas because the vast majority of energy we use — regardless of what country we live in — comes from burning something, usually coal, petroleum fuels, natural gas, or wood. More than 80 percent of U.S. energy in 2009 came from the combustion of fossil fuels.  Go here for more information about how combustion works.

WE’VE BURNED THINGS FOR EONS, WHY IS IT DIFFERENT NOW?

Plants and some types of microscopic organisms take carbon dioxide gas out of the air and turn it back into solid, carbon-based materials like plant fibers, using the energy of sunlight. The basis for all of our fuels, even the fossil fuels, comes from exploiting the fact that organisms convert  light energy into chemical energy, a potential energy source inside the plant or organism’s cells, whether the energy was converted in the last few decades (wood, biodiesel, ethanol) or millions of years ago (fossil fuels). Today, however, organisms don’t have the capacity to capture anywhere near as much of the greenhouse gas carbon dioxide as we produce, partly because we are burning fuels produced over millions of years.

EMISSIONS ARE A WORLDWIDE PHENOMENON

The United States produces more greenhouse gas each year per person than most other countries. However, even if we stopped producing any carbon dioxide at all, which is unlikely, the world would still keep producing 80 percent of its former output. Other regions produce just as much as we do, particularly Europe and China.

Furthermore, instead of holding steady at a particular emission rate, every year we use more energy and therefore emit more greenhouse gas. For a graph of atmospheric carbon dioxide by year, go here.

When we talk about energy-related emissions, we don’t only mean electricity. Energy involves burning oil and natural gas for heating, burning gasoline, diesel, and jet fuels for transportation. Transportation accounted for just over a third of all carbon dioxide emissions in 2009, electricity was almost 40 percent and residential, commercial, and industrial production, excluding electricity, made up roughly 26 percent.

Some greenhouse gases are thought to alter the climate more than others. Nitrous oxide is a much smaller percent of the gas mix than carbon dioxide, but for its weight it has a much stronger heat-trapping capability.

For more information go to The connection between greenhouse gases, climate change, and global warming.

Each year what proportion of emissions are man-made are carefully tracked by several agencies nationally and internationally, including the National Oceanic and Atmospheric Administration, the National Weather Service, and the National Aeronautics and Space Administration.

Sources:

U.S. Geological Survey
U.S. Energy Information Administration

U.S. Environmental Protection Agency
U.S. National Oceanic and Atmospheric Administration
CIA World Fact Book
World Energy Council
National Renewable Energy Laboratory
Emissions of Greenhouse Gases in the United States 2009: Independent Statistics & Analysis. U.S. Energy Information Administration, Department of Energy. March 2011.