Satellite measurements and a supercomputer model combine hypnotically in NASA’s latest triumph: an unprecedentedly detailed look at how planet-warming carbon dioxide moves through the Earth’s atmosphere.
In the visualization, the greenhouse gas can be seen gliding down the sides of mountain ranges, rushing across adjacent plains, and swirling from sea level to more than 12 miles skyward. The fires that engulfed Indonesia in late 2015 throw off more than half a billion tons of carbon dioxide. And as CO2-absorbing forests grow in summer and go dormant in winter, the atmospheric concentration of the gas falls and rise over the Northern Hemisphere—as if the Earth itself were breathing. (See also: “The Earth Has Lungs. Watch Them Breathe.”)
The slick video, however, is no mere show pony: It represents the first integration of NASA’s supercomputer climate models with data from OCO-2, a NASA satellite launched in 2014. OCO-2’s job is to keep constant tabs on global carbon dioxide levels. From its perch 436 miles above Earth’s surface, the satellite takes about one million measurements and nearly 100,000 carbon dioxide estimates per day. (Cloud cover interferes with some measurement.)
The satellite works by tracking the brightness of sunlight reflected off Earth’s surface, looking specifically at infrared wavelengths that oxygen and carbon dioxide absorb. By seeing how much light these gases absorb, scientists can tell how many gas molecules must have been present over a given area—letting them reconstruct carbon dioxide’s atmospheric concentration from space.
Only NASA could deliver such a view: The satellite borrows sensors from the Hubble Space Telescope, as well as from instruments designed to study Venus’s night side and its CO2-rich atmosphere.
Seeing CO2 from space marks a major advance, says NASA Jet Propulsion Laboratory scientist David Crisp, the science team leader for OCO-2. The land-based measurements available before were excellent—but they’re spotty.
“There are 150 or so stations at the surface of the earth that have been collecting incredibly precise measurements,” Crisp says. “But the world is a really big place, and there’s very interesting circulation patterns. It’s like trying to predict the weather across the earth with only 150 weather stations.”
Eye in the Sky
The data-spiked visualization—covering September 2014 to September 2015—will allow researchers to better understand how Earth’s atmosphere, lands, and oceans exchange carbon dioxide with one another.
Figuring out these exchanges is vital. Atmospheric CO2 concentrations have increased by more than 40 percent over the last two centuries to more than 400 parts per million, largely from human activities such as burning fossil fuels. Increased greenhouse gases have ushered in a worldwide warming trend that is changing Earth’s climate, with devastating consequences. (Read more about the reality of climate change in our November 2015 special issue.)
Right now, about half of the CO2 humans emit gets soaked up by the land and ocean. How fast Earth warms in the future will depend in part on how fast those “sinks” fill up—a fundamental question the OCO-2 satellite is designed to help answer.
What’s more, OCO-2 offers a high-resolution glimpse into how Earth’s climate naturally varies, such as the brutally strong El Niño that took hold in mid-2015. Crisp says that the satellite spotted its global impacts, including the 500 to 700 million tons of carbon dioxide emitted from Indonesia’s devastating 2015 fires, which El Niño made worse via a punishing drought.
In addition, Crisp says that OCO-2 saw how high temperatures across Africa and droughts and high temperatures in South America stalled plants’ growth, preventing them from absorbing CO2. In all, El Niño prevented the absorption of about 1.8 billion tons of CO2 across the two continents—the equivalent of nearly 5 percent of human emissions. The OCO-2 team presented these findings this week at the fall meeting of the American Geophysical Union.
“In Africa, we cooked the plants, in Indonesia, we burned the plants, and in South America, the plants shut down,” says Crisp. “These are all theories we’ve had in the past for why CO2 increases when we have a big El Niño—and hey, they’re all true.”
OCO-2’s original two-year mission ended this year, though the satellite continues to collect data daily. The satellite’s team is applying to NASA to extend the mission, and an unlaunched spare of OCO-2 is being retrofitted to become a future instrument aboard the International Space Station.
But the future of OCO-2 is unclear. Advisers to U.S. President-elect Donald Trump have expressed skepticism of NASA’s climate science studies.
“Even climate deniers have to admit the climate is changing, even if they don’t think it’s from human activity,” says Crisp. “As the climate changes, how are these processes we depend on changing, [such as] crops and plant health?”
Editor's note: This piece has been updated to clarify that while OCO-2's primary mission ended earlier this year, the satellite has continued its science operations.