The Orbiting Carbon Observatory-2 (OCO-2), which was launched on in July 2014 by NASA, is producing about 2 million observations per month of the atmospheric CO2 concentrations across the entire Earth with a spatial resolution of about three square kilometers. The satellite also detects solar-induced chlorophyll fluorescence (SIF), the small amount of light emitted during photosynthesis. The data collected by the OCO-2 mission is now being used to assess regional sources and sinks of CO2 around the globe and the first results have just been published.
The high-density observations from OCO-2, coupled with surface ocean CO2 measurements from NOAA buoys, have made it possible to track atmospheric CO2 concentrations during the 2015–2016 El Niño. The net impact of the 2015–2016 El Niño event was an increase in atmospheric CO2 concentrations. The three tropical continents made about similar contribution to the net carbon flux anomaly in 2015, but each continent was dominated by a different process. In tropical South America a drop in vegetation growth reduced carbon uptake (0.9 ± 0.96 gigatons C). In tropical Asia fire increased carbon release (0.4 ± 0.08 gigatons C). In Africa vegetation respiration increased carbon release (0.6 ± 1.01 gigatons C). Most of the excess carbon release in 2015 was associated with either extremely low precipitation or high temperatures, or both.
Initial analysis of the solar-induced chlorophyll fluorescence from OCO-2 suggests that SIF represents a good proxy for vegetation growth and the high-quality SIF from OCO-2 will provide valuable data for studying the terrestrial carbon cycle.
Measurements of atmospheric CO2 with a resolution of about three square km from OCO-2 allows distinct point sources of CO2 caused by known anthropogenic and natural point sources, including CO2 emissions from megacities and from volcanoes.
Influence of El Niño on atmospheric CO2 over the tropical Pacific Ocean: Findings from NASA’s OCO-2 mission, A. Chatterjee et al., Science 13 Oct 2017:Vol. 358, Issue 6360, eaam5776, DOI: 10.1126/science.aam5776