Good and bad news for the environment: while the ozone layer seems to be recovering, the concentration of greenhouse gases still seems to be on the rise. According to a study released this week by the World Meteorological Organization and the United Nations Environmental Program, the effect of the Montreal Protocol- created in response to a thinning ozone layer- is helping to repair the ozone. But levels of greenhouse gases are still critically high.

The Montreal Protocol specified the phase-out of harmful chemicals that could deplete the ozone, such as chlorofluorocarbons. The WMO’s study found that the Montreal Protocol’s effects had greatly benefited the ozone: chemical levels of chlorine and bromine were greatly reduced, and the ozone concentration appeared relatively stable. If the protocol is followed, the ozone layer could return to levels not seen since 1980.

Unfortunately, greenhouse gas emissions have risen to levels not seen since the 1980s. Carbon dioxide emissions increased 2.9% in 2013, bringing the level of CO2 up to 396 ppm (before the Industrial Revolution, levels were below 300 ppm). Concentrations of methane and nitrous oxide jumped as well. The WMO also warned that multiple gigatons of CO2 could be produced by harmful hydrofluorocarbons, which could add to the carbon dioxide concentrations.

While the ozone layer seems to be recovering, there’s still a troubling rise in greenhouse gas emissions- especially carbon dioxide. CO2 is harmful in that it contributes to acidification of the oceans, lowering the pH and potentially harming numerous species. The WMO’s study will play a major part in the coming UN summit in New York City on climate change.