TY - JOUR

T1 - Efficiency of short-lived halogens at influencing climate through depletion of stratospheric ozone

AU - Hossaini, R.

AU - Chipperfield, M. P.

AU - Montzka, S. A.

AU - Rap, A.

AU - Dhomse, S.

AU - Feng, W.

PY - 2015/3

Y1 - 2015/3

N2 - Halogens released from long-lived anthropogenic substances, such as chlorofluorocarbons, are the principal cause of recent depletion of stratospheric ozone, a greenhouse gas(1-3). Recent observations show that very short-lived substances, with lifetimes generally under six months, are also an important source of stratospheric halogens(4,5). Short-lived bromine substances are produced naturally by seaweed and phytoplankton, whereas short-lived chlorine substances are primarily anthropogenic. Here we used a chemical transport model to quantify the depletion of ozone in the lower stratosphere from short-lived halogen substances, and a radiative transfer model to quantify the radiative effects of that ozone depletion. According to our simulations, ozone loss from short-lived substances had a radiative effect nearly half that from long-lived halocarbons in 2011 and, since pre-industrial times, has contributed a total of about -0.02 W m(-2) to global radiative forcing. We find natural short-lived bromine substances exert a 3.6 times larger ozone radiative effect than long-lived halocarbons, normalized by halogen content, and show atmospheric levels of dichloromethane, a short-lived chlorine substance not controlled by the Montreal Protocol, are rapidly increasing. We conclude that potential further significant increases in the atmospheric abundance of short-lived halogen substances, through changing natural processes(6-8) or continued anthropogenic emissions(9), could be important for future climate.

AB - Halogens released from long-lived anthropogenic substances, such as chlorofluorocarbons, are the principal cause of recent depletion of stratospheric ozone, a greenhouse gas(1-3). Recent observations show that very short-lived substances, with lifetimes generally under six months, are also an important source of stratospheric halogens(4,5). Short-lived bromine substances are produced naturally by seaweed and phytoplankton, whereas short-lived chlorine substances are primarily anthropogenic. Here we used a chemical transport model to quantify the depletion of ozone in the lower stratosphere from short-lived halogen substances, and a radiative transfer model to quantify the radiative effects of that ozone depletion. According to our simulations, ozone loss from short-lived substances had a radiative effect nearly half that from long-lived halocarbons in 2011 and, since pre-industrial times, has contributed a total of about -0.02 W m(-2) to global radiative forcing. We find natural short-lived bromine substances exert a 3.6 times larger ozone radiative effect than long-lived halocarbons, normalized by halogen content, and show atmospheric levels of dichloromethane, a short-lived chlorine substance not controlled by the Montreal Protocol, are rapidly increasing. We conclude that potential further significant increases in the atmospheric abundance of short-lived halogen substances, through changing natural processes(6-8) or continued anthropogenic emissions(9), could be important for future climate.

KW - BROMINE

KW - TROPOSPHERE

KW - EMISSIONS

KW - IODINE

KW - SUBSTANCES

KW - TRENDS

KW - IMPACT

KW - MODEL

U2 - 10.1038/NGEO2363

DO - 10.1038/NGEO2363

M3 - Journal article

VL - 8

SP - 186

EP - 190

JO - Nature Geoscience

JF - Nature Geoscience

SN - 1752-0894

IS - 3

ER -