Fig. 3
Annual permafrost temperature change. a–d Permafrost temperature departure \({\mathrm{\Delta }}\bar T_{y,b}\) calculated from mean annual ground temperatures in boreholes near the depth of zero annual amplitude Z* relative to the 2008–2009 reference period. Mean values calculated as de-clustered, indexed area-weighted averages (Eq. 1). Temperature uncertainties are expressed at 95% confidence. Sample size shown is the number of borehole sites per year and region
