Emissions of a banned, ozone-depleting chemical are on the rise, a group of scientists reported Wednesday, suggesting someone may be secretly manufacturing the pollutant in violation of an international accord. Emissions of CFC-11 have climbed 25 percent since 2012, despite the chemical being part of a group of ozone pollutants that were phased out under the 1987 Montreal Protocol. “I’ve been making these measurements for more than 30 years, and this is the most surprising thing I’ve seen,” said Stephen Montzka, a scientist with the National Oceanic and Atmospheric Administration who led the work. “I was astounded by it, really.”...