Did You Know?
If it were not for naturally occurring greenhouse gases, the Earth would be too cold to support life as we know it. Without the greenhouse effect, the average temperature of the Earth would be about -2°F rather than the 57°F we currently experience.
However, levels of several important greenhouse gases have increased by about 40% since industrialization began around 150 years ago. During the past 20 years, about three-quarters of human-caused (anthropogenic) emissions came from burning fossil fuels. Concentrations of carbon dioxide in the atmosphere are naturally regulated by numerous processes collectively known as the "carbon cycle."
The flux, or movement, of carbon between the atmosphere and Earth's land and oceans is dominated by natural processes, including plant photosynthesis. While these natural processes can absorb some of the human-caused carbon dioxide emissions produced each year, an estimated 4.1 billion metric tons are added to the atmosphere each year.
Scientists know with virtual certainty that increasing greenhouse gas concentrations tend to warm the planet.1 Rising temperatures may, in turn, produce changes in weather patterns and sea level known as "climate change."
1. U.S. Environmental Protection Agency, Climate Change State of Knowledge