CO₂ is a critical component of the Earth's atmosphere. Since the beginning of the industrial age, the concentration of CO₂ has increased by about 38%, from about 280 parts per million to over 380 parts per million. Scientific studies indicate that CO₂ is one of several gases that trap heat near the surface of the Earth. These gases are known as greenhouse gases. Many scientists have concluded that substantial increases in the abundance of CO₂ will generate an increase in the Earth's surface temperature. Historical records provide evidence of this trend, which is often called global warming -- i.e., the overall increase Earth’s surface temperature globally. Current research indicates that continuing increases in atmospheric CO₂ may modify the environment in a variety of ways. In other words, although the Earth’s surface temperature may increase globally, specific regions on Earth may be affected differently. These changes may impact ocean currents, the jet stream and rain patterns. Some parts of the Earth might actually cool while the average temperature increases. Thus, a more appropriate term for this phenomenon is climate change.

CO₂ can enter the atmosphere from a variety of sources, which can be natural or anthropogenic. For example, some natural sources are rotting plants, forest fires and ordinary breathing. Automobiles, factories and home heating units burn fossil fuels such as oil, coal and natural gas. Burning these fossil fuels releases CO₂ into the atmosphere. These activities add to the emission of CO₂ into the atmosphere.

Processes that absorb CO₂ from the atmosphere are often referred to as sinks. Several natural processes remove CO₂ from the atmosphere. Plants, for example, use sunlight to photosynthesize CO₂ and water into sugar and other carbohydrates. Oceans also absorb atmospheric CO₂, whereafter, sea creatures incorporate the dissolved CO₂ into their shells. After these creatures die, their shells fall to the bottom of the ocean and eventually form carbonate rocks. The complete process of CO₂ exchange (taking into account both sources and sinks) is known as the carbon cycle.

To better understand the carbon cycle, the Carbon Dioxide Information Analysis Center of the U. S. Department of Energy tracks and monitors CO₂ emissions from a global network of ground-based sites. This network provides a tremendous amount of insight into the global abundance of CO₂ and its variability over changes in seasons. Unfortunately, the global network does not include enough stations to resolve the spatial distribution of CO₂ sources and sinks at the scale of continents or ocean basins. Thus, even with these extensive measurements, the processes that regulate the exchange of CO₂ between the atmosphere, the oceans, and the biosphere are not completely understood.

Using a space-based platform, OCO-2 will collect a greater number of high resolution measurements which in turn, will provide a greater spatial distribution of CO₂ over the entire globe. These measurements will be combined with data from the ground-based network to provide scientists with the information that they need to better understand the processes that regulate atmospheric CO₂ and its role in the carbon cycle. This enhanced understanding is essential for improving predictions of future atmospheric CO₂ increases and its impact on Earth's climate. This information will help policy makers and business leaders make better decisions to ensure climate stability and, at the same time, retain our quality of life.