Six Temperature Proxies of Scots Pine from the Interior of Northern Fennoscandia Combined in Three Frequency Ranges

Figure 4

Final linear regression models on June–August mean as target (dotted line) with various combinations of proxies recalibrated in 1908–2002 (solid line): (a) WA of all six h-f (30-year spline indexed) series, (b) WA of SRW, SXD, FXD, and RRW (four 180-year spline indexed, 4Spline) m-f series, and (c) WA of the SXD, FXD, and RRW (3RCS series).

(a) High-frequency model; all six 𝑅²=0.62

(b) Medium-frequency model; 4Spline 𝑅²=0.56

(c) Low-frequency model; 3RCS 𝑅²=0.59 (all six model 𝑅²=0.57)