Table 1.

Summary of which early warning indicator worked for which dataset. Symbols indicate the sign(s), and numerical values the mean ± s.d. of the Kendall trend statistics obtained when varying the sliding window length and (for ACF and variance) the filtering bandwidth.

	early warning signal?
dataset	ACF		DFA		variance
Vostok	−/+	0±0.32	−	−0.21±0.09	−(+)	−0.48±0.31
GISP2	+(−)	0.04±0.18	+	0.09±0.05	+	0.45±0.17
Cariaco	+(−)	0.42±0.22	+	0.37±0.06	−	−0.31±0.16
CLIMBER-2	+	0.64±0.24	+	0.65±0.10	+	0.79±0.16
GENIE-1	+	0.97±0.03	+	0.25±0.14	+	0.98±0.03
GENIE-2	+(−)	0.58±0.21	+	0.43±0.09	−(+)	−0.07±0.31