Measuring Carbon Dioxide and Nitrogen Dioxide Trends with Remote Sensing

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Most measurements of greenhouse gases uses a bottoms-up approach by estimating emissions based on reported fossil fuel consumptions from power plants and other sources.  Researchers from the University of Bremen recently published in Nature Geoscience the results of an effort to implement a top-down approach using data acquired remotely.

Data was pulled from the Sciamachy (SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY)  instrument on ESA’s Envisat satellite in order to measure nitrogen dioxide and carbon dioxide trends from 2003 to 2011.  Although Envisat stopped functioning in 2012, ten different instruments  (including the Advanced Synthetic Aperture Radar (ASAR) and Medium Resolution Imaging Spectrometer (MERIS) instruments) aboard the satellite collected data about Earth’s atmosphere, land, sea and ice from its more than 50,000 orbits around the earth over ten years.  The data is still be analyzed by scientists to learn more about the Earth’s processes.

The researchers used the measurements of both CO2 and NOx to be able to discern where and when carbon dioxide was being emitted.  The major source of NOx in the atmosphere is from the burning of fossil fuels.  Carbon dioxide emissions last for decades in the atmosphere whereas nitrogen dioxide has a relatively short lifetime that can be measured in hours.  Since Sciamachy measured nitrogen dioxide and carbon dioxide simultaneously, researchers were able to use NOx as a tracer to detect recent emissions of carbon dioxide into the atmosphere.  The researchers used a spatial high-pass filtering method to separate out man-made sources of carbon dioxide from those resulting from the release and uptake by vegetation.

This method allowed the researchers to see trends in day-to-day patterns of CO2 emissions.

Daily variation in CO2 emissions for North American and Europe. The green line shows the mean value and the grey shaded area the uncertainty and variability of the measurements. The graph shows that man-made sources of CO2 emissions drops on the weekends. Source: University of Bremen.

Daily variation in CO2 emissions for North American and Europe. The green line shows the mean value and the grey shaded area the uncertainty and variability of the measurements. The graph shows that man-made sources of CO2 emissions drops on the weekends. Source: University of Bremen.

Researchers were also able to map out global trends in carbon dioxide emissions between 2003 and 2011. The study showed that North America and Europe had a slight decrease in both carbon dioxide and nitrogen dioxide emissions.  East Asia, due to economic growth, showed an increase in carbon dioxide emissions but a corresponding smaller increase in nitrogen dioxide emissions due to the area’s use of cleaner technology.

Carbon dioxide emissions increased in East Asia (right) at an average rate of 9.8% per year from 2003 to 2011, but nitrogen oxides increased by ‘only’ 5.8% per year. This indicates a use of cleaner technology in East Asia. North America and Europe, however, show slightly decreasing trends for both gases. The maps show the corresponding spatial pattern as obtained from the satellite data: red corresponds to regions with high values of NOx and CO2, while blue indicates background values. Source: University of Bremen.

Carbon dioxide emissions increased in East Asia (right) at an average rate of 9.8% per year from 2003 to 2011, but nitrogen oxides increased by ‘only’ 5.8% per year. This indicates a use of cleaner technology in East Asia. North America and Europe, however, show slightly decreasing trends for both gases. The maps show the corresponding spatial pattern as obtained from the satellite data: red corresponds to regions with high values of NOx and CO2, while blue indicates background values. Source: University of Bremen.

Currently, no orbiting satellites have instruments that can directly observe carbon dioxide emissions.  CarbonSat is one of two possible options for ESA’s eighth Earth Explorer satellite being considered.

References

Decreasing emissions of NOx relative to CO2 in East Asia inferred from satellite observations.  2014.  M. Reuter, M. Buchwitz, A. Hilboll, A. Richter, O. Schneising, M. Hilker, J. Heymann, H. Bovensmann & J. P. Burrows.  Nature Geoscience  doi:10.1038/ngeo2257. Web. 29 Sept. 2014.

Good and Bad News for Our AtmosphereEuropean Space Agency. N.p., n.d. Web. 29 Sept. 2014.

 


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