Greenhouse gases are molecules in our atmosphere that absorb some of the infrared radiation emitted from Earth’s surface, keeping it from being re-released into space. This prevents some of the energy from reaching Earth and can have serious implications for our climate. The main greenhouse gases (in order of their atmospheric concentration) are water vapor, carbon dioxide, methane, nitrous oxide and a suite of fluorocarbons that are derived from industrial activities. Human activity has dramatically increased the volume of greenhouse gases in our atmosphere over the past one and a half centuries, causing a rise in global temperatures.
Generally, each greenhouse gas has an effect on the climate that is related to its concentration in the atmosphere and its ability to stay in the atmosphere for a long time, known as its atmospheric lifetime. This impact is measured using a metric called the “global warming potential,” which compares the heat-trapping properties of a gas to that of CO2 over a 100-year period.
Three-quarters of the human-made greenhouse gas emissions come from burning fossil fuels, such as coal, oil and natural gas, to produce electricity and power vehicles. Other significant sources are cement and steel production, fermentation of crops to make alcohol and pharmaceuticals, and the decomposition of organic material.
There are many ways to reduce your own personal greenhouse gas emissions. For example, drive less and use public transportation or ride a bike. When shopping for new appliances, look for the EnergyStar label—these products are more energy efficient and emit fewer greenhouse gases. Eat less meat, as cows are the largest producers of methane, and support renewable energy sources. And plant a tree–trees absorb carbon dioxide and help to keep it out of the atmosphere.