Greenhouse gases are particular types of gases present in the atmosphere that significantly regulate the temperature of the Earth. These allow the sun's energy to reach the Earth unimpeded, and trap some of the heat, energy and radiation which escapes at night.
Greenhouse gases are a natural phenomena that act as a heat filtration system, but the balance has recently been upset by human activity, which is rapidly increasing greenhouse gases quantities. Since the industrial revolution, greenhouse gas concentration in the Earth's atmosphere has increased constantly, and has risen exponentially in recent decades as populations boom and industrialisation spreads. Carbon dioxyde makes up the majority of all greenhouse gases emitted by human activity and is the largest naturally present greenhouse gas in the Earth's atmosphere.
In the United States, the principle activities producing CO2 are electricity generation, transportation and industrial production through fossile fuel combustion. Increasing greenhouse gas concentration levels has strong correlations to climate change and threatens plants and species the world over. But natural levels help maintain a temperature suitable to sustain life on Earth. Without any greenhouse gases, nights on Earth would deadly as the heat absorbed by the sun would not be retained in the atmosphere.