GNec_m.txt
Monthly mean group number from the Cliver & Ling (2016) reconstruction.
(-1 values indicate "no data"). Currently, no standard error values are available.
Col 1: Year
Col 2: Month
Col 3: Date in decimal year (middle of month)
Col 4: Group number Gn
Col 5: Standard error Eg. No value provided
Col 6: Number of days with observations