资源环境科技发展态势分析平台

Nonstationarity and time scale dependence are essential features of the climate system that may be dealt with simultaneously using wavelet analysis. In this study, we present a systematic analysis of a set of climate system variables, which include both natural and anthropogenic contributions, using wavelet-based exploratory methods. The tools of the continuous wavelet transform, the wavelet spectrum, coherence, and phase offer a comprehensive assessment of the characteristic modes of variability of climate system forcings and of the scale-based relationships of anthropogenic and natural climate variables with global surface temperature. Shorter-term variations in global surface temperature are associated with internally generated natural climate variability and external climate forcings, while longer-term variations are strongly related to human-induced changes only. In this respect, a long-term component of the net radiative forcing of human activities longer than 30 years displays a statistically significant relationship with global warming and cooling periods identified in the climate change literature.