How Important Is Convective Hydration of the Lower Stratosphere?

Recent work by us has shown that much of the trend in lower stratospheric humidity over the 21st century in chemistry-climate models is due to trends in evaporation of ice convectively lofted into the lower stratosphere.  On the other hand, analysis of observations over the last decade or so show that TTL temperatures provide the dominant control on lower stratospheric humidity.   In this talk, we provide evidence that convectively lofted ice had a (small) impact on lower stratospheric humidity over the past decade and explain why convective ice has a much bigger impact on long timescales than on short.  One should not take the dominance of TTL temperature variations in regulating lower stratospheric humidity over the past decade and infer that this is true on all timescales.