• The stratosphere, heated by the absorption of the solar radiation by the ozone, is by contrast a very stable layer.

• There has been a growing appreciation of the importance of the stratosphere in the climate system because of changes in its structure and recognition of the vital role of both radiative and dynamical processes.

• Increases in CO2 concentration are expected to cool the stratosphere, which is known to reduce the rates of gasphase ozone destruction in much of the stratosphere and thereby increase ozone concentrations at altitudes above about 25 km.