Temperature anomaly (TA) at the Earth’s surface at both hemispheres (red dashed line). Linear regressions of the TA are fitted by the EDA anomaly averages (absolute at panels a and b and percentage at panels c and d) computed from the combined data of ionosonde stations Boulder, Juliusruh, Slough/Chilton Kokubunji and Wakkanai in the Northern hemisphere (panels a and c) and by the ionosonde stations Brisbane, Canberra, Hobart and Port Stanley from the Southern hemisphere (panels b and d). To get a coincidence of linear fits for TA and EDA, absolute EDA averages have been scaled by a divisor as indicated and offset by several years indicated by T_D in the plots.