Naturally occurring bromine- and iodine-containing compounds
substantially reduce regional, and possibly even global, tropospheric ozone
levels. As such, these halogen gases reduce the global warming effects of ozone
in the troposphere, and its capacity to initiate the chemical removal of
hydrocarbons such as methane. The majority of halogen-related surface ozone
destruction is attributable to iodine chemistry. So far, organic iodine
compounds have been assumed to serve as the main source of oceanic iodine
emissions. However, known organic sources of atmospheric iodine cannot account
for gas-phase iodine oxide concentrations in the lower troposphere over the
tropical oceans.