Introduction

Abstract

Climate is all about variability. Imagine a world in which temperature and other meteorological elements would not vary in time and space. There would be no need for the term “climate”. In reality, it may be cool today but warm tomorrow (Fig. 1.1, left). Travelling a few hundred kilometres away, one may find a very different weather situation upon arrival (Fig. 1.1, right). These variations may not be predictable more than a few days ahead, but there are typical spatial patterns and temporal evolutions in this variability. The term climate describes these typical variations and aims at bringing an order to them. Climatic changes, then, are changes in these typical variations over time.