Just a few weeks ago, Secretary of State John Kerry admitted that “one of the most successful environmental agreements in history” was actually now a huge driver of climate change. Late last week, Kerry went further, saying that “HFCs [hydrofluorocarbons], which was supposed to be the solution, turned out not to be the solution,” but can actually be “thousands of times more damaging than carbon dioxide.”

Now, 170 countries, including the U.S., have agreed to cut the use of HFCs, used in many cooling and refrigeration system. The Montreal Protocol in 1987 phased out CFCs (chlorofluorocarbons) which were blamed for ozone depletion and causing the infamous “hole” in the ozone layer of the earth’s atmosphere. Kerry credits the introduction of HFCs with saving the ozone layer, but acknowledges there were unintended consequences.