Anomalous climate dynamics induced by multiplicative and additive noises.

Abstract

Anomalous behavior of a nonlinear climate-vegetation model governed by the multiplicative and additive noises is revealed on the basis of stochastic sensitivity analysis. A specific feature of this model is the bistability with the coexistence of "snowball" equilibrium and "warm" attractor in the form of equilibrium or cycle. It is found that multiplicative and additive noises shift probabilistic distribution in opposite directions. The multiplicative noise introduced into the death rate of vegetation changes the dispersion of random states and their localization in the phase diagram. This type of noise cools down the system and is responsible for its transition to the snowball state. On the contrary, the additive noise warms up the climate with increasing noise intensity. A cumulative effect of multiplicative and additive noises occurs under their simultaneous influence. This effect determining the evolutionary behavior of a climate-vegetation system depends on the ratio of intensities of these noises.