Greenhouse Gases
Greenhouse gases trap heat in the atmosphere, which makes the Earth warmer. People are adding several types of greenhouse gases to the atmosphere, and each gas's effect on climate change depends on three main factors:
People produce larger amounts of some greenhouse gases than others. Carbon dioxide is the greenhouse gas you hear people talk about the most. That's because we produce more carbon dioxide than any other greenhouse gas, and it's responsible for most of the warming.
Some greenhouse gases stay in the atmosphere for only a short time, but others can stay in the atmosphere and affect the climate for thousands of years.
Not all greenhouse gases are created equal! Some trap more heat than others. For example, one pound of methane traps about 21 times as much heat as one pound of carbon dioxide. Learn more.
Carbon dioxide is the most important greenhouse gas emitted by humans, but several other gases contribute to climate change, too. Learn more about the major greenhouse gases by selecting pieces of the pie chart below.
Water Vapor: It's a Gas!
Water can take the form of an invisible gas called water vapor. Water vapor is naturally present in the atmosphere and has a strong effect on weather and climate.
As the planet gets warmer, more water evaporates from the Earth's surface and becomes vapor in the atmosphere. Water vapor is a greenhouse gas, so more water vapor in the atmosphere leads to even more warming. This is an example of a positive feedback loop, which happens when warming causes changes that lead to even more warming.
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The size of each piece of the pie represents the amount of warming that each gas is currently causing in the atmosphere as a result of emissions from people's activities. Source: Intergovernmental Panel on Climate Change, Fifth Assessment Report (2014).
Greenhouse gases come from all sorts of everyday activities, such as using electricity, heating our homes, and driving around town. The graph to the right shows which activities produce the most greenhouse gases in the United States.
These greenhouse gases don't just stay in one place after they're added to the atmosphere. As air moves around the world, greenhouse gases become globally mixed, which means the concentration of a greenhouse gas like carbon dioxide is roughly the same no matter where you measure it. Even though some countries produce more greenhouse gases than others, emissions from every country contribute to the problem. That's one reason why climate change requires global action. The graph below shows how the world's total greenhouse gas emissions are continuing to increase every year.
Water Vapor: It's a Gas!
Water can take the form of an invisible gas called water vapor. Water vapor is naturally present in the atmosphere and has a strong effect on weather and climate.
As the planet gets warmer, more water evaporates from the Earth's surface and becomes vapor in the atmosphere. Water vapor is a greenhouse gas, so more water vapor in the atmosphere leads to even more warming. This is an example of a positive feedback loop, which happens when warming causes changes that lead to even more warming.