Human activities can alter the atmosphere.
Starting in the mid-1700s, human activities began to alter the composition of the atmosphere. Vast supplies of charcoal, and later coal and oil, fed the growing fires of the Industrial Revolution. The carbon stored in these fuels was released to the air as carbon dioxide - a gas that traps heat in the atmosphere. Today, for every one of the more than 5.8 billion people on Earth, nearly six tons of carbon dioxide are spewed into the air annually. As a result of our activities, the atmospheric concentration of this heat-trapping gas has risen by more than 30 percent in the last 250 years.