Abstract/Summary

How might the processes generating clear-air turbulence change in a warmer world? We know that observations support an association between clear-air turbulence and shear instability. We also know that the upper atmospheric wind shears are changing in response to greenhouse gas forcing. In particular, theoretical reasoning and climate model simulations both suggest that the vertical shear in horizontal wind is increasing in magnitude at typical aircraft cruising altitudes in the middle latitudes, especially in the winter months in each hemisphere. This increased shearing implies that clear-air turbulence may itself be changing as a consequence of climate change. This chapter reviews the various lines of observational and model-based evidence for trends in clear-air turbulence, by analyzing data from turbulence encounters with aircraft, turbulence diagnosed from reanalysis datasets, passenger injuries caused by turbulence, and turbulence diagnosed from climate models. The possibility of anthropogenic trends in clear-air turbulence opens up a whole new field of academic study, which exists at the interface between the two scientific disciplines of aviation turbulence and climate change. We call for future work to improve our understanding of this poorly understood but potentially important impact of climate change.