SSTs, nitrogen fertilizer and stratospheric ozone

Abstract

THE threat to stratospheric ozone from supersonic transport (SST) exhaust emissions has been a subject of controversy since Hampson1 first suggested that significant ozone reductions might be caused by discharged water vapour. Later, after Johnston2 and Crutzen3 pointed out that even larger ozone depletions might result from emitted nitrogen oxides, water vapour effects were considered to be relatively unimportant. In the intervening years, predictions of SST ozone modification have evolved with advancing scientific knowledge4–7. Using a recently revised model of the stratosphere8, we report here that a substantial ozone layer enhancement could accompany worldwide SST fleet operations, and that water vapour may be an important factor in SST assessments. We have also found that increased nitrogen fertiliser use might, likewise, enhance the ozone layer, in contrast with previous calculations of ozone reduction9–11.