Using high resolution global climate models to project trends in atmospheric turbulence.

Clear-air turbulence (CAT) has a large impact on the aviation sector. Our current understanding of how CAT may increase with climate change in future is largely based on simulations from CMIP3 and CMIP5 global climate models (GCMs). However, these models have now been superseded by high-resolution CMIP6 GCMs, which have grid lengths at which median individual turbulence patches may start to be resolved. Using a CMIP6 multi-model approach, projected CAT changes over the North Atlantic have been quantified. Twenty-one CAT diagnostics are used, to represent the uncertainties in CAT production mechanisms. Each diagnostic responds differently in time, but the majority display an increase in CAT between 1950 and 2050. These results refer to Northern Hemisphere (NH) CAT changes, particularly over the North Atlantic basin. Although NH winter is historically the most turbulent season, there is strong multi-model agreement that autumn and summer will have the greatest overall percentage increase in CAT frequency. Future NH summers are projected to become as turbulent as 1950 winters. Using the global-mean seasonal near-surface temperature as a comparative metric, with every of global near-surface warming, NH autumn, winter, spring, and summer are projected to have an average of 14%, 8%, 8%, and 14% more moderate CAT, respectively.