Left: Thermal fields retrieved from CH₄ emission from Cassini/CIRS, averaged between 1280–1320 cm⁻¹, sensitive to the millibar levels in the stratosphere, as a function of longitude and time. The temperatures correspond to an average between 25-45°N in latitude. Data before 2012 are presented in Fletcher et al. (2012), and data after the beginning of 2012 have not been published yet. Middle: Same as the left figure, but after realigning the beacon centre at 180° W in longitude. The performed alignment results in the data points of Fig. 4. The interpolation and smoothing of this figure is illustrated in the right panel to better see the extension of the beacon over time.