By Jonathan Amos
18 December 2014
(BBC News) – NASA's Orbiting Carbon Observatory (OCO-2) has returned its first global maps of the greenhouse gas CO2.
The satellite was sent up in July to help pinpoint the key locations on the Earth's surface where carbon dioxide is being emitted and absorbed.
This should help scientists better understand how human activities are influencing the climate.
The new maps contain only a few weeks of data in October and November, but demonstrate the promise of the mission.
Clearly evident within the charts is the banding effect that describes how emitted gases are mixed by winds along latitudes rather than across them.
Also apparent are the higher concentrations over South America and southern Africa. These are likely the result of biomass burning in these regions.
It is possible to see spikes, too, on the eastern seaboard of the US and over China. These probably include the additional emissions of CO2 that come from industrialisation.
"We're very early into the mission and collecting data, yet as we show, we can take five weeks of that information and give you a quick picture of global carbon dioxide," said deputy project scientist Annmarie Eldering.
"It really suggests to us that OCO-2 will be very useful for finding out about where carbon dioxide is coming from and being taken back up around the globe," she told BBC News. [...]
Humans add something like 40 billion tonnes of the gas to the atmosphere every year, principally from the burning of fossil fuels.
But the ultimate destination of this carbon dioxide is uncertain. About half is thought to be absorbed into the oceans, with the rest pulled down into land "sinks".
It is hoped OCO-2 can describe those draw-down locations in much more detail. [more]
18 December 2014 (NASA) – The first global maps of atmospheric carbon dioxide from NASA's new Orbiting Carbon Observatory-2 mission demonstrate its performance and promise, showing elevated carbon dioxide concentrations across the Southern Hemisphere from springtime biomass burning.
At a media briefing today at the American Geophysical Union meeting in San Francisco, scientists from NASA's Jet Propulsion Laboratory, Pasadena, California; Colorado State University (CSU), Fort Collins; and the California Institute of Technology, Pasadena, presented the maps of carbon dioxide and a related phenomenon known as solar-induced chlorophyll fluorescence and discussed their potential implications.
A global map covering Oct. 1 through Nov. 17 shows elevated carbon dioxide concentrations in the atmosphere above northern Australia, southern Africa and eastern Brazil.
"Preliminary analysis shows these signals are largely driven by the seasonal burning of savannas and forests," said OCO-2 Deputy Project Scientist Annmarie Eldering, of JPL. The team is comparing these measurements with data from other satellites to clarify how much of the observed concentration is likely due to biomass burning.
The time period covered by the new maps is spring in the Southern Hemisphere, when agricultural fires and land clearing are widespread. The impact of these activities on global carbon dioxide has not been well quantified. As OCO-2 acquires more data, Eldering said, its Southern Hemisphere measurements could lead to an improved understanding of the relative importance in these regions of photosynthesis in tropical plants, which removes carbon dioxide from the atmosphere, and biomass burning, which releases carbon dioxide to the atmosphere.
The early OCO-2 data hint at some potential surprises to come. "The agreement between OCO-2 and models based on existing carbon dioxide data is remarkably good, but there are some interesting differences," said Christopher O'Dell, an assistant professor at CSU and member of OCO-2's science team. "Some of the differences may be due to systematic errors in our measurements, and we are currently in the process of nailing these down. But some of the differences are likely due to gaps in our current knowledge of carbon sources in certain regions -- gaps that OCO-2 will help fill in."
Carbon dioxide in the atmosphere has no distinguishing features to show what its source was. Elevated carbon dioxide over a region could have a natural cause -- for example, a drought that reduces plant growth -- or a human cause. At today's briefing, JPL scientist Christian Frankenberg introduced a map using a new type of data analysis from OCO-2 that can help scientists distinguish the gas's natural sources.
Through photosynthesis, plants remove carbon dioxide from the air and use sunlight to synthesize the carbon into food. Plants end up re-emitting about one percent of the sunlight at longer wavelengths. Using one of OCO-2's three spectrometer instruments, scientists can measure the re-emitted light, known as solar-induced chlorophyll fluorescence (SIF). This measurement complements OCO-2's carbon dioxide data with information on when and where plants are drawing carbon from the atmosphere.
"Where OCO-2 really excels is the sheer amount of data being collected within a day, about one million measurements across a narrow swath," Frankenberg said. "For fluorescence, this enables us, for the first time, to look at features on the five- to 10-kilometer scale on a daily basis." SIF can be measured even through moderately thick clouds, so it will be especially useful in understanding regions like the Amazon where cloud cover thwarts most spaceborne observations.
The changes in atmospheric carbon dioxide that OCO-2 seeks to measure are so small that the mission must take unusual precautions to ensure the instrument is free of errors. For that reason, the spacecraft was designed so that it can make an extra maneuver. In addition to gathering a straight line of data like a lawnmower swath, the instrument can point at a single target on the ground for a total of seven minutes as it passes overhead. That requires the spacecraft to turn sideways and make a half cartwheel to keep the target in its sights.
The targets OCO-2 uses are stations in the Total Carbon Column Observing Network (TCCON), a collaborative effort of multiple international institutions. TCCON has been collecting carbon dioxide data for about five years, and its measurements are fully calibrated and extremely accurate. At the same time that OCO-2 targets a TCCON site, a ground-based instrument at the site makes the same measurement. The extent to which the two measurements agree indicates how well calibrated the OCO-2 sensors are.
Additional maps released today showed the results of these targeting maneuvers over two TCCON sites in California and one in Australia. "Early results are very promising," said Paul Wennberg, a professor at Caltech and head of the TCCON network. "Over the next few months, the team will refine the OCO-2 data, and we anticipate that these comparisons will continue to improve."
To learn more about OCO-2, visit:
Caltech manages JPL for NASA.
NASA monitors Earth's vital signs from land, air and space with a fleet of satellites and ambitious airborne and ground-based observation campaigns. NASA develops new ways to observe and study Earth's interconnected natural systems with long-term data records and computer analysis tools to better see how our planet is changing. The agency shares this unique knowledge with the global community and works with institutions in the United States and around the world that contribute to understanding and protecting our home planet.
For more information about NASA's Earth science activities this year, see:
Jet Propulsion Laboratory, Pasadena, Calif.
Written by Carol Rasmussen
NASA Earth Science News Team