Atmosphere of Earth However, polar stratospheric or nacreous clouds are occasionally seen in the lower part of this layer of the atmosphere where the air is coldest. The stratosphere is the highest layer that can be accessed by jet-powered aircraft. The troposphere is the lowest layer of Earth's atmosphere. It extends from Earth's surface to an average height of about , although this altitude varies from about at the geographic poles to at the Equator, with some variation due to weather. The troposphere is bounded above by the tropopause, a boundary marked in most places by a temperature inversion (i.e. a layer of
Vienna Convention for the Protection of the Ozone Layer Groups that help facilitate functions under the convention. A Multilateral Fund exists to aid developing nations transition from ozone-depleting chemicals using guidelines under the convention, which is administered by a Multilateral Fund Secretariat. The Multilateral Fund has aided thousands of projects in nearly 150 countries, preventing the usage of roughly 250,000 tons of ozone-depleting chemicals. Vienna Convention for the Protection of the Ozone Layer The Vienna Convention for the Protection of the Ozone Layer is a multilateral environmental agreement signed in 1985 that provided frameworks for international reductions in the production of chlorofluorocarbons due to their contribution to the destruction