Global warming is the process by which the Earth’s average atmospheric temperature increases over time. The Earth has experienced both global warming and cooling during its 4.5-billion-year history. However, the current rate of temperature increase exceeds that which occurred in the past. Many scientists suspect that the accelerated rate of temperature increase is the result of human behavior.
The primary driving force behind global warming is the change in the chemical composition of the Earth’s atmosphere. By burning hydrocarbons, humans release elevated levels of carbon dioxide into the air. As the atmosphere’s carbon concentration goes up, the planet retains more of the heat from the sun. The process works similarly to the way a greenhouse does, which is why scientists refer to carbon dioxide as a “greenhouse gas.” Carbon dioxide is not the only greenhouse gas, but it is the most important one for humans to monitor. Methane, nitrous oxide and fluorinated gases also contribute to global warming.
Rising temperatures cause a variety of effects on the planet. While a few of these effects are beneficial, most are detrimental to the current balance of nature. For example, rising carbon dioxide levels may cause plants to grow more quickly, but the accompanying rise in temperature may cause the polar ice caps to melt, raising the global sea level.