Top panel: T_CMB as a function of redshift. The red filled circles represent T_CMB measured from the tSZ emission law in redshift bins of Planck clusters. The green star shows COBE-FIRAS measurement at z = 0 (Fixsen 2009). The orange crosses show T_CMB measurements using individual clusters (Battistelli et al. 2002; Luzzi et al. 2009). Dark-blue triangles represent measurements from C_I and C_II absorption (Cui et al. 2005; Ge et al. 1997; Srianand et al. 2000; Molaro et al. 2002) at z = (1.8,2.0,2.3,3.0). Blue diamonds show the measurements from CO absorption lines (Srianand et al. 2008; Noterdaeme et al. 2011), and finally the light-blue asterisk is the constraint from various molecular species analyses by Muller et al. (2013). The solid black line presents the standard evolution for T_CMB and the dashed black line represents our best-fitting model combining all the measurements. The 1 and 2σ envelopes are displayed as shaded dark and light-gray regions. Bottom panel: deviation from the standard evolution in units of standard deviation. The dashed and dotted black lines correspond to the 1 and 2σ levels.