Kinetic temperatures derived from Doppler broadening in various absorption-line systems as a function of the total H I column densities of these systems. Empty circles correspond to measurements obtained thanks to the presence of deuterium (typically in one or a few close components) while filled squares correspond to average measurements in complex systems made possible by high-resolution spectroscopy. Grey triangles represent measurements in individual components of the DLA towards HE 0001−2340 (Fig. 3). The data exhibit an anti-correlation with a Pearson coefficient of r = −0.78 and a probability that this is pure coincidence of p = 0.16%. The solid blue (respectively red) line corresponds to an unweighted linear fit including (resp. excluding) the lowest N(H I) value towards Q 1009+2956.