Linear and Nonlinear Aspects of Climate Response to External Forcings

Abstract

The main role in the current climate change is played by anthropogenic forcings, primarily anthropogenic emissions of greenhouse gases and aerosols. On the global scale, the response of the Earth system to these forcings is close to linear. In particular, it depends mostly on the magnitude of such forcings and only weakly on their nature and spatial localization. However, even with relatively small (in absolute value) external forcings, the response of the characteristics of the Earth system can be essentially nonlinear with the manifestation of tipping points, upon transition through which the behavior of the Earth’s climate changes qualitatively. Examples are given for linear and nonlinear mechanisms of the climate response to external forcings.