Researchers at the University of Copenhagen have found that acidity in the atmosphere is almost back at the level it was before industrialization.
By studying the Greenland ice sheet, they were able to analyze atmospheric composition over time. The various layers of the ice sheet are composed of snow that fell during different time periods, but never melted. By pulling out ice cores, the scientists can study water that was once in the atmosphere at any given time in history (up to about 125,000 years ago).
A file photo of the Greenland ice sheet, which covers about 80 percent of Greenland. Milan Petrovic/Shutterstock
