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A similar comparison for the transition from 1988 to 1989 in ERA-Interim (Fig. 2) reveals that in the troposphere and stratosphere (from 1000 hPa to 1 hPa), the differences are, on the whole, of a similar magnitude to those in the 2009/2010 ERA5 transition. However, in the lower to mid-mesosphere (from 1 hPa to 0.1 hPa, with the latter being the top of the ERA-Interim domain), the differences in the ERA-Interim transition are generally smaller than in the 2009/2010 ERA5 transition, having magnitudes less than 2 K, except near the equator at about 0.8 hPa where the magnitudes exceed 3 K. The spread in temperature, for September - November 2009, in the ERA5 10 member ensemble (Fig. 3), which gives some indication of the uncertainty, shows that the largest values are located at lower latitudes, in the mid to upper stratosphere, where values exceed 0.8 K. This region merges into a second area of relatively large uncertainty, in the mesosphere of the northern hemisphere, where values exceed 0.7 K in the mid-latitudes of the mid-mesosphere.