Plants take in carbon dioxide from the air and give off oxygen.
Animals and people take in oxygen and give off carbon dioxide. The result is a natural balance that serves the needs of all living things. However, certain events upset the oxygen-carbon dioxide balance. One result could be global warming.
What Causes Global Warming?
When the gases in the atmosphere are not in balance, Earth’s climate is affected. Many scientists say carbon dioxide is on the increase. With more carbon dioxide in the atmosphere, more heat gets trapped. That can lead to global warming.

Trouble: Fewer Plants
Plants use carbon dioxide for photosynthesis. With fewer rain forest plants on Earth, less carbon dioxide is removed from the atmosphere. The result is an increase in carbon dioxide.
Trouble: Burning Fossil Fuels
Coal, oil, and natural gas are called fossil fuels. They’re made of plant or animal remains from millions of years ago. Burning them—and burning wood—releases lots of carbon dioxide into the air. More and more fossil fuels are being burned each year.
Trouble: Thawing Permafrost
Plants give off carbon dioxide when they decompose, or rot. Plants in the tundra don’t rot when they die. They stay frozen in the permafrost. Because of global warming, the permafrost is thawing, and the dead plants are rotting. Now even more carbon dioxide is going into the atmosphere, and that increases global warming.
Trouble: Burning Rain Forests
When large areas of rain forest are burned, huge amounts of carbon dioxide go into the air. That throws off the oxygen-carbon dioxide balance. Every second, one and a half acres of rain forest gets burned or cut down, some sources say. The land is then used for farming or ranching.
Trouble: Heat in the Atmosphere
The gases in the atmosphere act like the glass in a greenhouse. They let in some sunlight to heat Earth. Some of the heat is absorbed on Earth, and some bounces back into the atmosphere, where the carbon dioxide traps it. With more carbon dioxide in Earth’s atmosphere, more heat gets trapped. As the planet warms, even by a fraction of a degree, glaciers begin to melt, and permafrost begins to thaw. These changes cause even more changes.
Trouble: Fewer Clouds, Less Rain
When water evaporates from the leaves of rain forest plants, it helps clouds form. Clouds bring rain. As rain forests are cut or burned down, the climate gets drier. Rain forests around the world are being destroyed. Scientists believe this has led to droughts and crop failures.