Climate change may hinder the ozone recovery, the World Meteorological Organization (WMO) said ahead of the 20th anniversary of the signing of the Montreal Protocol on substances that deplete the ozone layer.

The Montreal Protocol is designed to protect the ozone layer by banning substances believed to be responsible for ozone depletion, like chlorofluorocarbons (CFC). The UN meteorology agency said the production of CFCs declined over the past years, but nations across the globe must remain vigilant and prevent climate change.

“Global changes in climate mean that conditions in the atmosphere are different today from those that prevailed prior to periods marked by ozone depletion. The changes in conditions may indeed have implications for ozone recovery,” WMO Secretary-General Michel Jarraud said Friday.

Jarraud was speaking in Geneva nearly two decades after the Protocol was opened for signature on September 16 1987.

“Over the next ten to twenty years, high quality global observations of ozone and ozone-depleting substances will be particularly critical in verifying the effectiveness of the actions taken under the Vienna Convention in 1985, the Montreal Protocol of 1987 and its amendments and adjustments,” the scientist and a meteorologist added.

Experts found out that greenhouse gases, responsible for global warming, are cooling the atmosphere and accelerate ozone depletion. They say climate change represents a serious threat for the layer’s recovery, even if CFC emissions are under control.

Latest studies revealed that the much-needed ozone layer, which protects us from the harmful effects of the ultraviolet rays, is depleting dramatically especially over the Antarctic region.

The WMO said the hole over the Antarctic reached a record size of 29.5 million square kilometres last year. The agency said preliminary assessments couldn’t reveal the evolution of the hole this year.

UN Secretary-General Ban Ki-moon said Thursday that the Montreal Protocol, signed by 24 states, is “one of the great success stories of international cooperation.”

Representatives of 191 nations are expected to attend the conference which kicks off Sunday in Montreal. The meeting aims at imposing new measures that would permit a tighter grip on the production of CFCs and hydrochlorofluorocarbons, a group of chemical compounds believed to have the same noxious effect.