Equivalent effective stratospheric chlorine (EESC) provides an estimate of the total effective amount of halogens (

chlorine Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...

and

bromine Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest element in group 17 of the periodic table (halogens) and is a volatile red-brown liquid at room temperature that evaporates readily to form a simila ...

) in the

stratosphere The stratosphere () is the second layer of the atmosphere of the Earth, located above the troposphere and below the mesosphere. The stratosphere is an atmospheric layer composed of stratified temperature layers, with the warm layers of air ...

. It is calculated from emission of

chlorofluorocarbon Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and prop ...

and related halogenated compounds into the

troposphere The troposphere is the first and lowest layer of the atmosphere of the Earth, and contains 75% of the total mass of the planetary atmosphere, 99% of the total mass of water vapour and aerosols, and is where most weather phenomena occur. From ...

(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 (

).Newman, P. A., Daniel, J. S., Waugh, D. W., and Nash, E. R.: A new formulation of equivalent effective stratospheric chlorine (EESC), Atmos. Chem. Phys., 7, 4537-4552, , 2007. This parameter is used to quantify man-made

ozone depletion Ozone depletion consists of two related events observed since the late 1970s: a steady lowering of about four percent in the total amount of ozone in Earth's atmosphere, and a much larger springtime decrease in stratospheric ozone (the ozone l ...

and its changes with time. As a consequence of the

Montreal Protocol The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion Ozone depletion consists of two related events observed sinc ...

and its amendments phasing out ozone-depleting substances (ODS), the EESC reached maximum in the late 1990s and is now slowly decreasing.

References

{{Reflist, 1 Ozone depletion