Orbiting Carbon Observatory-2OCO-2
Since launching in 2014, OCO-2 has become widely regarded as the “gold standard” in CO2 measurements from space. OCO-2 measurements have been used to quantify
how CO2 emissions are offset by natural carbon sinks like forests and
oceans and how those carbon sinks can be transformed to carbon emitters due to drought, deforestation, or wildfires. As extreme events intensify with global warming, tracking changes to our carbon sinks will be increasingly important. The mission has also uncovered insights into CO2 emissions from cities, and contributes data supporting the Paris Agreement. As an unexpected bonus, OCO-2 has even been able to track growing seasons and crops by measuring the “glow” plants emit when they photosynthesize.
The original science objectives of the OCO-2 mission were to collect the space-based measurements needed to quantify variations in the column averaged atmospheric carbon dioxide (CO2) dry air mole fraction, XCO2, with the precision, resolution, and coverage needed to improve our understanding of surface CO2 sources and sinks (fluxes) on regional scales (≥1000km) and the processes controlling their variability over the seasonal cycle. The OCO-2 mission has met these original objectives and is enabling new insights into Earth’s carbon cycle. OCO-2 continues to serve as a pathfinder mission that validates a space-based measurement approach and analysis concept that can be used for future systematic CO2 monitoring missions.
CO2 is one of the primary greenhouse gases on Earth. Greenhouse gases are those which can trap thermal radiation or heat that the Earth would otherwise emit to space.
CO2 is an important gas for life on the planet and integral to maintaining the protective blanket that is our atmosphere. However, sharp increases or decreases may affect the delicate atmospheric balance, and increases in atmospheric CO2 concentration may adversely alter the global climate.
The Earth system maintains a check and balance on CO2 through the carbon cycle and what we call sources and sinks. A source is any process where CO2 is released into the atmosphere such as plant and animal decay, deforestation, when we breathe out, or the burning of fossil fuels such as coal or gas. A sink is a reservoir that removes some of the CO2 from the atmosphere, such as when vegetation and trees take up CO2 for photosynthesis. The oceans remove some of the CO2 from the atmosphere as well.
The nature and the locations of the sinks that absorb about half of the human produced CO2 are currently not well known and present important, yet unanswered questions. For example, if the efficiency of these sinks decreases in the future, will the rate of buildup of atmospheric CO2increase? If so, how much? Can some of these natural sinks be exploited to further reduce the rate of CO2 buildup? By better understanding the nature, locations, and processes that make these natural sinks, we can better predict the rate of buildup of CO2 in the atmosphere and its impact on our climate.
Today, fossil fuel combustion and other human activities are contributing tens of billions tons (gigatons) of CO2 into the atmosphere each year. This is only a small fraction of the hundreds of Gigatons of CO2 emitted into the atmosphere each year by natural processes in the ocean and on land. However, unlike the human activities, which only emit CO2into the atmosphere, these same natural processes absorb as well as emit CO2. In fact, atmospheric CO2 measurements collected by a global network of surface stations indicate that these natural CO2 "sinks” not only absorb almost all of the CO2 emitted by natural processes, they also absorb almost half of the CO2 that is being emitted by human activities as well. Further information on carbon emissions and the ramifications for reaching global climate goals can be obtained here.
The concentration of CO2 in the atmosphere is measured in “parts per million by volume” (ppmv). For example, in 1970, atmospheric measurements indicated that about 330 out of every million air molecules was a CO2 molecule, yielding a concentration of 330 ppmv.In recent decades, human emissions have increased the CO2 concentration at an every-increasing rate, such that by 2024, the atmospheric CO2 concentration had increased to values over 420 ppmv. This is impacting the Earth's climate.
OCO-2 measurements provide the global coverage, spatial resolution, and accuracy needed to characterize and monitor the geographic distribution of CO2 sources and sinks and quantify their variability. Based on these measurements, scientists are able to map the natural and man-made processes that regulate the exchange of CO2 between the Earth's surface and the atmosphere on local, regional and continental scales.