The last El Nino in 2015-16 impacted the amount of carbon dioxide that Earth’s tropical regions released into the atmosphere, leading to Earth’s recent record spike in atmospheric carbon dioxide. The effects of the El Niño were different in each region. Photo: NASA/JPL-Caltech

Three hotspots at the Equator, warmed by the most recent El Niño, drove a sharp spike in global carbon dioxide increases in 2015 and 2016, according to observations from a NASA satellite.

The three hotspots are massive swaths of tropical forest in South America, Africa, and Indonesia, which were all impacted by hotter and drier weather leading to larger carbon increases than ever before, scientists said.

The carbon increases were 50 percent greater globally during the two years – and were driven mostly by the 2.5 additional gigatons from the three hotspots, said scientists running the NASA Orbiting Carbon Observatory-2.

“Understanding how the carbon cycle in these regions responded to El Niño will enable scientists to improve carbon cycle models, which should lead to improved predictions of how our planet may respond to similar conditions in the future,” said Annmarie Eldering, of NASA’s Jet Propulsion Laboratory, who is the OCO-2 deputy project scientist.

The three hotspots were all impacted by El Niño’s heat, and then passed on the effects globally.

For instance, in South America, 2015 was the driest year in decades. Higher-than-average temperatures combined with those climatic conditions to stress massive amounts of plant life, meaning there was less photosynthesis than normal – and thus less carbon was removed from the atmosphere than normal.

Tropical forests in eastern Africa had normal rainfall, but the temperatures were much greater than normal. More death and decomposition of the flora in the region caused more carbon production that was not offset by the living plants.

Indonesia was similar to South America in that it was the second-driest year in 30 years. But those dry conditions created massive forest and peat fires, which drove the carbon increases there, according to the NASA observations.

“We knew El Niños were one factor in these variations, but until now we didn’t understand, at the scale of these regions, what the most important processes were,” added Eldering. “The team’s findings imply that if future climate brings more or longer droughts, as the last El Niño did, more carbon dioxide may remain in the atmosphere, leading to a tendency to further warm Earth.”

The paper showing the OCO-2 findings was published this week in the journal Science. Among other observations included relatively small carbon differences over the city of Los Angeles, and plumes of three volcanoes on Vanuatu.

OCO-2 was launched in 2014.