  The Cassini/Composite InfraRed Spectrometer (CIRS) instrument has been
observing the middle atmosphere of Titan over almost half a Saturnian year. We
used the CIRS dataset processed through the up-to-date calibration pipeline to
characterize seasonal changes of temperature and abundance profiles in the
middle atmosphere of Titan, from mid-northern winter to early northern summer
all around the satellite. We used limb spectra from 590 to 1500 cm$^{-1}$ at
0.5-cm$^{-1}$ spectral resolution, which allows us to probe different
altitudes. We averaged the limb spectra recorded during each flyby on a fixed
altitude grid to increase the signal-to-noise ratio. These thermal infrared
data were analyzed by means of a radiative transfer code coupled with an
inversion algorithm, in order to retrieve vertical temperature and abundance
profiles. These profiles cover an altitude range of approximately 100 to 600
km, at 10- or 40-km vertical resolution (depending on the observation). Strong
changes in temperature and composition occur in both polar regions where a
vortex is in place during the winter. At this season, we observe a global
enrichment in photochemical compounds in the mesosphere and stratosphere and a
hot stratopause located around 0.01 mbar, both linked to downwelling in a
pole-to-pole circulation cell. After the northern spring equinox, between
December 2009 and April 2010, a stronger enhancement of photochemical compounds
occurred at the north pole above the 0.01-mbar region, likely due to combined
photochemical and dynamical effects. During the southern autumn in 2015, above
the South pole, we also observed a strong enrichment in photochemical compounds
that contributed to the cooling of the stratosphere above 0.2 mbar. Close to
the northern spring equinox, in December 2009, the thermal profile at 74{\deg}N
exhibits an oscillation that we interpret in terms of an inertia-gravity wave.
