Estimation of frequency response of the global temperature to change in radiative forcing

Abstract

The Earth’s climate system (ECS) is considered as a linear system whose input is a change in the solar constant ΔI( t) and the output is an anomaly of the globally averaged surface temperature ΔT( t). The system input can be affected by other factors, and at the output their own temperature fluctuations and a random noise manifest themselves. All these factors are assumed to be independent of ΔI( t). The spectral analysis of monthly mean values of ΔI( t) and ΔT( t) shows the existence of statistically significant coherence. The amplitude-frequency response A( f) of the ECS is different from zero up to the Nyquist’s frequency 0.5 month−1. The results areconsistent with the previously obtained estimate of the equivalent time constant of the ESC 1.31 ± 0.03 month.