Freon is a proud product developed by DuPont Company in the 193s, which is widely used in refrigerants and solvents. Halon plays an important role in fire fighting and other industries, such as plastic foaming agents, aerosol sprays and electronic cleaning agents. When scientists' research convincingly reveals that human activities have caused serious depletion of the ozone layer, the action of "mending the sky" is very rapid. In fact, few scientific problems in modern society have developed from fierce opposition and incomprehension to concerted action by all mankind to protect them.
In p>1985, eleven years after Monlina and Rowland put forward the ozone depletion mechanism of chlorine atom, it was also the year when the Antarctic ozone hole was discovered, which was initiated by the United Nations Environment Programme. Through the Vienna Convention for the Protection of the Ozone Layer, a series of principles and guidelines for controlling ozone layer destruction have been established for the first time in the world.
In p>1987, the Montreal Protocol, an important historical document for the protection of the atmospheric ozone layer, was adopted. In this protocol, the types of controlled substances and the phasing-out schedule for ozone layer protection are specified, and the global freon is required to be reduced by half by the year 2, and the control measures for the production, consumption, import and export of freon substances are formulated.
As further scientific research showed that the situation of ozone depletion in the atmosphere was more severe, the London Amendment to the Montreal Protocol was adopted in 199. In 1992, the Copenhagen Amendment was adopted, in which the types of controlled substances were expanded again and the schedule of complete elimination was advanced again and again.
From here, we can not only see the increasingly urgent pace of mankind, but also find that even if we make such efforts to make up the "ozone hole" above us, it is very difficult to remove ozone-depleting substances from the atmosphere. It is estimated that the concentration of stratospheric hydrogen atoms will not drop below the critical level until around 25 by adopting the Copenhagen Amendment. By then, the "ozone hole" above us is expected to begin to recover. Ozone layer protection is a typical example of global cooperation in modern history. This cooperation mechanism will become the wealth of mankind and provide reference and experience for solving other major problems.