Sub-Saharan Africa produces less CO2 than Europe

November 10th, 2016, Published in Articles: EE Publishers, Articles: EngineerIT

 

Scientists have produced the first global maps of human emissions of carbon dioxide ever made solely from satellite observations of the greenhouse gas. The maps, based on data from NASA’s Orbiting Carbon Observatory-2 (OCO-2) satellite and generated with a new data-processing technique, agree well with inventories of known carbon dioxide emissions.

Artists impression of OCO 2. Credit JPL

Artist’s impression of OCO-2. Credit JPL

No satellite before OCO-2 was capable of measuring carbon dioxide in fine enough detail to allow researchers to create maps of human emissions from the satellite data alone. Instead, earlier maps also incorporated estimates from economic data and modelling results.

The team of scientists from the Finnish Meteorological Institute, Helsinki, produced three main maps from OCO-2 data, each centred on one of Earth’s highest-emitting regions: the eastern United States, central Europe and East Asia. The maps show widespread carbon dioxide across major urban areas and smaller pockets of high emissions.

“OCO-2 can even detect smaller, isolated emitting areas like individual cities,” said research scientist Janne Hakkarainen, who led the study. “It’s a very powerful tool that gives new insight.”

Human emissions of carbon dioxide have grown at a significant rate since the Industrial Revolution, and the greenhouse gas lingers in the atmosphere for a century or more. This means that recent human output is only a tiny part of the total carbon dioxide that OCO-2 records as it looks down toward Earth’s surface. “Currently, the background level of carbon dioxide in the atmosphere is about 400 parts per million, and human emissions within the past year may add only something like three parts per million to that total,” said Hakkarainen. The data-processing challenge, he noted, was to isolate the signature of the recent emissions from the total amount.

Human carbon dioxide emissions over Europe, the Middle East and northern Africa. Values range from 3 parts per million CO2 below background levels (navy blue) to 3 parts per million above (pale yellow). High emissions over Germany and Poland (top centre) and Kuwait and Iraq (right) mostly come from fossil fuel burning, but over sub-Saharan Africa they mostly come from fires. Credit: FMI

Human carbon dioxide emissions over Europe, the Middle East and northern Africa. Values range from three parts per million CO2 below background levels (navy blue) to three parts per million above (pale yellow). High emissions over Germany and Poland (top centre) and Kuwait and Iraq (right) mostly come from fossil fuel burning, but over sub-Saharan Africa they mostly come from fires. Credit: FMI

NASA successfully launched its first spacecraft dedicated to studying atmospheric carbon dioxide on 2 July 2014. Orbiting Carbon Observatory-2 (OCO-2) is NASA’s first dedicated Earth remote sensing satellite to study atmospheric carbon dioxide from space. OCO-2 is an exploratory science mission designed to collect space-based global measurements of atmospheric CO2 with the precision, resolution, and coverage needed to characterise sources and sinks (fluxes) on regional scales (≥1000km). OCO-2 will also be able to quantify CO2 variability over the seasonal cycles year after year. This mission will also validate a space-based measurement approach and analysis concept that could be used for future systematic CO2 monitoring missions.

The Finnish Meteorological Institute team’s new data-processing technique accounts for seasonal changes in carbon dioxide, the result of plant growth and dormancy, as well as the background carbon dioxide level. To be sure their method was correct, they compared the results with measurements of nitrogen dioxide — another gas emitted from fossil fuel combustion — from the Ozone Monitoring Instrument, a Dutch-Finnish instrument on NASA’s Aura satellite. OMI and OCO-2 are both in the A-Train satellite constellation, so the two measurements cover the same area of Earth and are separated in time by only 15 minutes.

The two measurements correlated well, giving the researchers confidence that their new technique produced reliable results. The research demonstrates the possibility of analysing joint satellite observations of carbon dioxide and other gases related to combustion processes to draw out information about the emissions sources.

NASA develops new ways to observe and study Earth’s interconnected natural systems with long-term data records. The agency freely shares this unique knowledge and works with institutions around the world to gain new insights into how our planet is changing. A global network of ground-based measurement sites has observed an increase in atmospheric CO2 concentration by almost 20% over the past 50 years – the most dramatic change that has ever been seen in human history. The amount of CO2 added to the atmosphere through human activities, according to the Global Carbon Project (GCP), has been steadily climbing.

The world’s oceans, plants and soils on land, and numerous other less significant carbon pools within the global carbon cycle steadily absorb carbon and are called sinks. They serve to reduce the amount of CO2 that remains in the atmosphere. However, the geographic distributions of carbon uptakes by the oceans and terrestrial ecosystems are still uncertain. In addition, the effectiveness and efficiency of these sinks may change over time as more CO2 is emitted into the atmosphere and, therefore, warrant study.

 

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