CO2 emissions linked to El Niño hint at a warmer future

2015-2016 was a record year for atmospheric carbon, and NASA's Orbiting Carbon Observatory-2 (OCO-2) captured all of it. In a series of papers published Thursday in the journal Science, NASA researchers report using the satellites to pinpoint ways in which the years' strong El Niño exacerbated a series of carbon-emitting events around the globe.

Why it matters: "If future climate is more like this recent El Niño, the trouble is the Earth may actually lose some of the carbon removal services we get from these tropical forests, and then CO2 will increase even faster in the atmosphere," said Scott Denning, an OCO-2 scientist at a NASA press conference.

Why they did it: All told, 3 billion more metric tons of carbon were released in 2015 than 2011. But in 2015, CO2 emissions directly from human activities were fairly stable, so scientists wanted to know why the atmospheric levels were so high. The OCO-2 identifies natural and unnatural sources of carbon. According to OCO-2's estimates, roughly 80% of the extra CO2 emitted in 2015 could be linked to El Niño.

Drought in the Amazon: Drought-stressed rainforest plants take up CO2 more slowly than plants with enough water. Tropical rainforests are considered some of the most important carbon sinks on the planet, and play a key role in keeping CO2 levels in check.

Indonesian Fires: El Niño caused an unusually arid dry season in Indonesia, which allowed for the rapid spread of wildfires. As the forests burned, they released some the CO2 the trees had previously absorbed. The resulting haze stretched across much of Southeast Asia, and researchers estimate it may have been responsible for over 90,000 premature deaths. It should be noted that while El Niño contributed to the size and severity of Indonesia's catastrophic fires, they were initially started as illegal slash-and-burn land clearing.

Warmer Africa: Researchers think higher temperatures in Africa caused dead plants to decompose faster, a process that releases CO2.

Another study showed it's possible to locate precise sources of CO2, including cities and volcanoes.