Equivalent effective stratospheric chlorine
Encyclopedia
Equivalent effective stratospheric chlorine (EESC) provides an estimate of the total effective amount of halogens (chlorine
and bromine
) in the stratosphere
. It is calculated from emission of chlorofluorocarbon
and related halogenated compounds into the troposphere
(lower atmosphere) and their efficiency in contributing to stratospheric ozone depletion (ozone depletion potential, ODP), and by making assumptions on transport times into the upper atmosphere (stratosphere
). This parameter is used to quantify man-made ozone depletion
and its changes with time. As a consequence of the Montreal Protocol
and its amendments phasing out ozone-depleting substances (ODS), the EESC reached maximum in the late 1990s and is now slowly decreasing.
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
and bromine
Bromine
Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...
) in the stratosphere
Stratosphere
The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...
. It is calculated from emission of chlorofluorocarbon
Chlorofluorocarbon
A chlorofluorocarbon is an organic compound that contains carbon, chlorine, and fluorine, produced as a volatile derivative of methane and ethane. A common subclass are the hydrochlorofluorocarbons , which contain hydrogen, as well. They are also commonly known by the DuPont trade name Freon...
and related halogenated compounds into the troposphere
Troposphere
The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 80% of the atmosphere's mass and 99% of its water vapor and aerosols....
(lower atmosphere) and their efficiency in contributing to stratospheric ozone depletion (ozone depletion potential, ODP), and by making assumptions on transport times into the upper atmosphere (stratosphere
Stratosphere
The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...
). This parameter is used to quantify man-made ozone depletion
Ozone depletion
Ozone depletion describes two distinct but related phenomena observed since the late 1970s: a steady decline of about 4% per decade in the total volume of ozone in Earth's stratosphere , and a much larger springtime decrease in stratospheric ozone over Earth's polar regions. The latter phenomenon...
and its changes with time. As a consequence of the Montreal Protocol
Montreal Protocol
The Montreal Protocol on Substances That Deplete the Ozone Layer is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances believed to be responsible for ozone depletion...
and its amendments phasing out ozone-depleting substances (ODS), the EESC reached maximum in the late 1990s and is now slowly decreasing.