But since the 1800s, when people started burning carbon-rich fuels like coal and oil for energy, carbon dioxide has been building up in the atmosphere, trapping heat and warming the planet. The natural carbon cycle typically absorbs about half of that output. That’s driven carbon dioxide concentrations upward by about 45 percent since 1750, to more than 400 parts per million today.
In a series of papers published in the research journal Science, Eldering and her colleagues used OCO-2 data to illustrate how Indonesia’s massive forest fires, a hotter, drier Amazon, and a warmer Africa added about 3 parts per million to that count. The tonnage emitted was about a quarter of what humans add to the atmosphere every year, said Scott Denning, a University of Northern Colorado atmospheric scientist.
“Each region responded differently, but all of them added to the increase,” Denning told reporters at a NASA news conference.
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Southeast Asia saw its second-driest year on record in 2015, and massive forest fires — many of them set to clear land for agriculture — turned carbon stored in trees and peat beds into CO2. In South America, hot, dry weather stunted plant growth, while warmer weather and relatively normal rainfall boosted the contributions of decaying biomass, said Junjie Liu, a research scientist at JPL.
“In terms of how much of human emissions are the natural systems taking out and dampening the effects, this suggests that dampening is going to slow down,” Eldering said. “So we need to be mindful of that when we consider emissions in the future.”
OCO-2 uses a spectrometer to calculate carbon dioxide levels by how sunlight reflects off CO2 in the air and can detect the fluorescence emitted by plants during photosynthesis. That’s allowed scientists to shed light on the carbon cycle in parts of the world where measurements were difficult before, Eldering said.
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Before 2009, most carbon dioxide concentrations came from ground stations, and places like the remote oceans or much of Africa had few regular measurements. A Japanese satellite, GOSAT, started taking readings from space in 2009. And OCO-2, which replaced a craft lost in a launch failure the same year, “lets you find more smaller signals and signals that are impacting smaller regions of the world.”
Its planned follow-up, OCO-3, would be installed on the International Space Station, but faces political obstacles: The Trump administration wants to scrub the project as part of steep proposed cuts to NASA’s Earth science programs, but a Senate bill working its way through Congress would keep the money flowing.
However, NASA Earth Sciences Division chief Michael Freilich told reporters that the Trump administration’s budget fully funds another satellite, the Geostationary Carbon Cycle Observatory, which would go aloft in 2022.
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