Climate change

The course summarises our knowledge of the climate system and the way that it operates. We begin by looking at radiative transfer in the atmosphere and how energy moves between different levels and forms. We will introduce the concepts of radiative forcing and climate sensitivity, and show how simple models can predict specific features of the behaviour of the climate system, resulting in particular in multiple equilibria. We move next to the atmosphere, ocean, and cryosphere. We look at the polar vortex, the jet stream, and other mechanisms by which energy is transferred within the atmosphere. Similarly, we will explain fundamental processes characterising the oceanic circulation, notably the presence of gyres, coastal and equatorial upwelling, the formation of the density-driven circulation and how this interacts with the cryosphere. Then we look at the climate record, including the extreme past before the climate was cool enough to exhibit periodic ice ages. To explain these historical oscillations of climate we need to examine how carbon transfer processes affect and modulate climate change, over a wide range of time scales. Having introduced the main elements of the climate system we will then examine the basic principles on which climate models are based and describe their main limitations. This will help us in interpreting modelling results for different future scenarios.

Introduction: Definition of climate, main processes, evidence of recent climate changes Radiative transfer: Solar radiation, the atmosphere as a filter, aerosols and clouds Radiative forcing, Climate sensitivity, feedbacks Atmospheric and oceanic circulation Climate reconstruction: metrology, the history of the climate Carbon cycle: Mechanisms of carbon transfer, capture and storage in the climate system Climate modelling: assumptions, input data, results, sensitivity Possible scenarios: Influence of different processes, regional climate change