Carbon dioxide (CO₂) is a gas in the air that helps keep our planet warm, like a blanket around the Earth. When the Sun’s heat reaches Earth, some of it is reflected back into space, but CO₂ traps some of that heat, keeping the planet at a comfortable temperature. This natural process is called the greenhouse effect.
For most of Earth’s history, CO₂ levels and temperature were in balance. Scientists learned about this by studying natural records like ice cores, tree rings, and ocean sediments. These natural “time capsules” reveal that over millions of years, Earth’s temperature rose and fell in response to CO₂ levels. Since the late 1800s, scientists have also been using thermometers, weather stations, and later satellites to directly measure Earth’s temperature. These records show a rapid rise in global temperature over the past century.
In the last 200 years, humans have been adding a lot more CO₂ to the air by burning fossil fuels like coal, oil, and gas for energy. Cutting down forests—which naturally absorb CO₂—has made the problem worse. As a result, CO₂ levels in the atmosphere have increased by 50%, trapping more heat and making Earth hotter than it should be. This warming of the planet is called climate change.
Climate change affects weather patterns around the world. It causes stronger storms, hotter summers, melting ice, and rising sea levels. These changes are hard on animals, plants, and people. Scientists say we need to act now by switching to cleaner energy sources like wind and solar power, planting more trees, and finding ways to reduce CO₂ emissions.