A new study finds that earth’s oceans and lands continue to absorb more than half of the human-caused greenhouse gas emissions, suggesting that the planet has not yet reached its carbon-storage capacity even as emissions continue to escalate. Writing in the journal Nature, a team of U.S. scientists calculate that the world’s natural systems — including seas, forests, and soils — have absorbed about 55 percent of the roughly 350 billion tons of greenhouse gases emitted during the last 50 years. With human-based emissions rising steadily over five decades, those systems have had to absorb an ever-increasing amount of carbon, storing an estimated 5 billion tons in 2010 compared with 2.4 billion tons in 1960, the study found. These calculations are consistent with findings by the Global Carbon Project, according to Reuters. The planet’s capacity to store carbon has been a critical factor in preventing an even greater increase in global temperatures, but authors of the new study say that storage capacity will not remain indefinitely. “It’s not a question of whether or not natural sinks will slow their uptake of carbon, but when,” said Ashley Ballantyne, a researcher at the University of Colorado and lead author of the study.