Large floating contraptions, used by scientists to predict the acidity in the oceans, sit offshore the scientific outpost of Ny-Alesund. The cold water at the poles is able to absorb more carbon dioxide than tropical waters and therefore increases acidity quicker. Though it is a relatively small amount, the effects on the ocean's chemistry can be dramatic. Martin Bureau | AFP | Getty Images

Humans worried about climate change are getting some help from Earth — for now. Earth's land and ocean currently absorb about half of all carbon dioxide emissions from the burning of fossil fuels and other sources. But the amount of carbon entering the atmosphere may be changing nature in ways that leave scientists uncertain whether the planet can keep absorbing even that amount of carbon in the future.

Since the Industrial Revolution, carbon levels have increased 2.5 times to more than 400 parts per million at present, said Michael Freilich, director of NASA's Earth Science Division, in a call with reporters Thursday. That is higher than it has been in the last 400,000 years.

He added that scientists know, from ice cores and other information, that carbon levels in the atmosphere hovered between 180 and 280 parts per million until about the 1800s.

Freilich and his colleagues at NASA and other institutions discussed the need for more research into how the planet absorbs greenhouse gases, such as carbon dioxide. They also discussed new evidence taken from Orbiting Carbon Observatory-2 — NASA's first satellite designed to measure carbon dioxide "from the top of Earth's atmosphere to its surface," according to a NASA press release.

The data from space gives a significant advantage in getting an idea of the total carbon cycle around the entire planet, said Annmarie Eldering, OCO-2 deputy project scientist at NASA's jet propulsion laboratory in Pasadena, California.

On average about half of all of the carbon that enters the atmosphere is absorbed by the ocean or by forests — though that can vary, and some evidence suggests the increased levels of carbon in the ocean may be creating conditions — such as raised acidity levels in seawater — that are making it more difficult to absorb carbon, said Scott Doney, chair of the Marine Chemistry and Geochemistry Department of the Woods Hole Oceanographic Institute. "The land and the ocean are really doing us a big favor," said Lesley Ott, an atmospheric scientist in the Global Modeling and Assimilation Office at NASA's Goddard Space Flight Center in Greenbelt, Maryland, in a press release. "Otherwise you would have carbon building up in the atmosphere twice as fast as it does now."



Forests on land — increasingly prone to wildfires — may be emitting more carbon than they take in, as well. Wildfires were rampant across much of the western United States in 2015. Research released this year said wildfire seasons are lasting longer almost everywhere on the planet. Even Alaska saw an unusually high number of wildfires this year. Warming is also causing permafrost on the world's tundras to thaw, which is releasing greenhouse gases into the atmosphere as well, according to research. Even natural gas harvesting is leaking small amounts of methane into the air, and there are questions about whether that could be making any contribution to the total amounts of gases in the air, Doney said.