When did the Montreal Protocol come into effect?

The Montreal Protocol, an international treaty designed to phase out the production and consumption of substances that deplete the ozone layer, came into effect on January 1, 1989. This significant date marked the formal commitment of signatory nations to take action against ozone-depleting substances, which includes chlorofluorocarbons (CFCs) and halons, among others. The protocol has been pivotal in protecting the ozone layer and has been the foundation for subsequent agreements to strengthen global commitments to environmental protection and sustainability.

The other dates provided do not accurately represent the start date of the protocol's implementation, which clearly highlights the importance of the year 1989 in the context of global environmental policies. The Montreal Protocol's effectiveness upon that date has led to considerable progress in reducing harmful emissions and fostering international cooperation in environmental protection.