Introduction

The aim of climate modeling is to understand past changes in climate that are currently unexplained and to be able to predict successfully the future evolution of climate. This chapter begins with some general considerations on climate dynamics followed by an introduction to climate models, how they are constructed, the role of different models, what needs to be specified, and the need for data-model comparison and assimilation. The second half of the chapter is dedicated to the results of two modeling applications. The first one concerns the stability of global climate during the Holocene. The astronomical theory of paleoclimates is now sufficiently well understood to enable a prediction of the next glacial inception. We will see that it is not expected for 50 000 years but, paradoxically, this conclusion does not contradict a recent postulate that glacial inception would be occurring by now in the absence of an early anthropogenic perturbation. The second result focuses on the stability of the ocean-atmosphere system. Advective and convective processes in the deep-ocean may introduce stochastic effects. As a consequence, a specific event, such as an abrupt cooling, cannot necessarily be traced back to a well-identified cause.

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