Until recently, efforts to measure and model climate change contained a greater degree of uncertainty than scientists would prefer. This was due to the limitations of ground-based monitoring stations and satellites that collect data about carbon dioxide.
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But that's changing due to NASA's Orbiting Carbon Observatory-2 satellite, which is designed to provide a more precise and complete view of how carbon dioxide moves through the atmosphere, as well as between the atmosphere and plants, soil and the oceans.
"Carbon can't hide anymore," NASA climate scientist Lesley Ott explained in a telephone interview.
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The satellite measures the number of molecules of CO2 and air between the surface and outer space by analyzing wavelengths of light that CO2 absorbs. It takes 24 readings each second and provides measurements that are accurate to 0.25 percent. It's also capable of providing information about regions where there's poor coverage by ground-based sampling.
Those capabilities allow climate researchers "to see the kind of gradients that we need for good science," Ott said.
The $465 million satellite, launched in 2014, has now amassed more than a year's worth of data, and it's helping scientists to see both the sources of carbon dioxide emissions and also the sinks -- that is, places where carbon is stored. OCO-2's information could help them to fill in some gaps in their knowledge, and to get a clearer idea of much the Earth's climate will change in the future.
"We already know that plants and the ocean absorb half of human carbon emissions, which is doing us a big favor," Ott said. "But we haven't understood where that CO2 is being sequestered, and what are the processes that do it."
One key question that scientists need to answer is how climate change will affect the carbon-storing capacity of forests, Ott said. In the short term, it may actually boost forests' ability to serve as carbon sinks, because the CO2 acts "like a fertilizer in the ground," causing more and bigger plants to grow. "But we know that can't happen indefinitely," she said. "That makes it important to understand the sensitivity of that process to moisture and higher temperatures."
Paul Wennberg, director of the Ronald and Maxine Linde Center for Global Environmental Science at California Institute of Technology, wrote in an email that OCO-2 already has provided new insights about atmospheric exchange of carbon dioxide with forests in the upper latitudes, whose growth is likely be affected by climate change.
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"In particular, we are able to see much better the changing pattern of CO2 uptake during spring," Wennberg wrote. "One of the very exciting new products from OCO-2 is the so-called 'solar induced fluorescence (SIF)' -- a measure of the active hotosynthesis by plants. Combining the SIF and CO2 data from OCO-2 we can essentially image the onset of spring as it begins in Europe, spreads across Asia and finally arrived in North America."
According to a news release from NASA's Jet Propulsion Laboratory in Pasadena, Calif., OCO-2's data also shows the dynamic ebb and flow of atmospheric carbon according to the seasons. Between mid-May and mid-July, for example, it detected a "dramatic" reduction in atmospheric CO2 of 2 to 3 percent, as plants absorbed it from the atmosphere and used to form new leaves, stems and roots. Scientists were able to observe the "spring drawdown," as they call it, in detail, seeing week-to-week changes.
The satellite also detected increased concentrations of C02 in areas where fossil fuels are being burned by power plants and large cities, as well as in the Amazon, central Africa and Indonesia, where forests are being slashed and burned to clear fields for farming.
Ott said that scientists are still in the process of writing papers about the data, which unfortunately won't be published in time to have any impact on negotiations at the UN climate conference in Paris at the end of November. But those conclusions could figure in future talks.
Here's a NASA animation that visualizes a year's worth of data about carbon's movement in the atmosphere.