Projected advances of the GDD5≥1200 boundary. The green area describes the current extent of the boreal region66,67. GDD5 values were estimated by averaging the projections of seven CO2 emission based GCMs (Extended Data Table 1). Each time step describes a five-year average of all estimates by the seven GCMs. The variability in projection among models is presented in Fig. 4 and Table 1. Map created using ArcGIS Desktop v. 10.4.165.