The tiny envelope of gas and aerosol surrounding planet Earth comprises less than 1/1,000,000 of its mass, yet it is essential to life as we know it. The atmosphere contains the oxygen we breathe, an ozone layer that protects us from solar ultraviolet radiation and clouds that redistribute water from oceans to land. The atmosphere also makes the planet warm enough for life by trapping heat from the Sun.

This map shows sulfur dioxide in the atmosphere 100 days after the 1991 volcanic eruption of Mt. Pinatubo.

Human activities, such as the burning of fossil fuels, industrial and agricultural production, and deforestation, have changed the atmosphere dramatically over the past few hundred years. Carbon dioxide levels have increased by 30 percent, total chlorine by 75 percent and methane by 150 percent. Because of its relatively small mass, the atmosphere is very sensitive to change and can serve as an early-warning signal of long-term climate change.

JPL scientists are contributing in many ways to our understanding of how the Earth system works. They are looking for possible connections between rising levels of aerosols, in the form of soot and dust, and certain gases, and changes in climate and ozone levels. JPL projects are also monitoring the effects of regional pollution on ozone and other chemicals in the lower atmosphere.