Relaxation RC system. (a) Equivalent circuit. (b) Temporal response. (c) Phase difference (dark curves) and amplitude (gray curve, log scale) of response. Note that the maximum phase difference is 3 months. The dot represents the radiation-temperature system, where the warmest (coldest) day is about one month after the “longest” (“shortest”) day, indicating a relaxation time of about 0.1 year (1.2 months).