• Ozone (O3) is found naturally in the lower 10-15 km of the atmosphere (known as the troposphere) in minute concentrations.

• Ozone (O3) is an important greenhouse gas present in both the stratosphere and troposphere.

• To fully meet the initial request of the SBSTA (i.e., to discuss the temperature and sea level implications of the emissions limitation proposals) in a comprehensive manner, it would be necessary to cover the full range of possible concentrations (taking into account sinks and sources) of other gases such as methane (CH4), nitrous oxide (N2O), tropospheric ozone (O3) and the halocarbons § , along with the full range of possibilities for sulphate aerosols § derived from sulphur dioxide (SO2) emissions.