Montreal protocol was connected with

Hint: The Montreal Protocol was signed in 1987 and was effective from 1989 in Montreal (Canada) to control the emissions of ozone-depleting substances.

Complete Answer:
- The Montreal Protocol was established to provide a shield from the substances which affect the ozone layer. It was signed on $16^{th}$ September 1987 to the Vienna Convention for the Protection of the ozone layer.
- The treaty is formed around some halogenated hydrocarbons to deplete stratospheric ozone.
- The substance affecting ozone layers is chlorine or bromine but the substance in which fluorine is present does not harm ozone layers. There are some substances such as nitrous oxide that are not controlled by the Montreal Protocol.
- After the Montreal Protocol comes into action the concentration of atmospheric chlorofluorocarbons associated with chlorinated hydrocarbons has either leveled off or decreased.
- Mostly, the hydrochlorofluorocarbons and hydrofluorocarbons are now believed to donate to anthropogenic global warming.
- The $25^{th}$ anniversary of signing the Montreal Protocol striking in the year 2012. The Montreal Protocol was first designed to control the CFCs emitted from the refrigerator and halon but now it includes HCFCs and methyl bromide and other ozone-depleting substances.

Note: With the action of the Montreal Protocol the ozone depletion over Antarctica is now almost decreased with reduced production of chlorofluorocarbons and other harmful substances that deplete the ozone layers.