Radiative forcing due to trends in stratospheric water vapour

Trends derived from the latest version of Halo- gen Occultation Experiment (HALOE) data are used in a two-dimensional atmospheric model to estimate their radia- tive eects over the last decade. The results show a strato- spheric cooling in regions of H2O increase, of magnitude similar to that due to stratospheric ozone loss indicating a signicant additional cause of observed stratospheric tem- perature decreases. Radiative forcings are derived and it is found that global average radiative forcing due to strato- sphericwatervapourchangesprobablyliesintherange0.12 to 0.20 Wm 2 decade 1 . This could have more than com- pensated for the negative radiative forcing due to decadal ozone loss.

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