Climate System Dynamics and Modelling

Our short journey in climate science is close to its end. It has shown the diversity of the domain and has provided a sample of the large number of processes potentially responsible for climate variations on a wide range of time and spatial scales. This diversity is exciting because it allows us to create the links with pre-existing knowledge, learned in other textbooks and lectures, whilst stimulating our curiosity about many additional applications and topics not covered here. It is also frustrating because the content of an introductory textbook should be as self-sufficient as possible. Ideally, new points had to be demonstrated or justified, relying on standard skills in mathematics and physics, for instance, with a few references for additional lectures. The main mechanisms included in the preceding chapters are all explained qualitatively, often using schematics, and many of them quantitatively too. Nevertheless, determining the stability criteria of a numerical scheme or estimating precisely the magnitude of a feedback requires techniques which cannot all be described in detail here. Only the conclusions of existing studies can be given, with some general information on the method(s) applied. I hope that this will encourage many readers to go deeper into the topics that appear the most promising for them to investigate by themselves how precisely those conclusions are reached and the strong scientific arguments behind them.

Many of the cited references are recent, showing the rapid development of this knowledge. This situation also underlines the fact that uncertainties are still present on the subject addressed, justifying the current intense scientific activity. These uncertainties have been mentioned several times in this text, but it is important to recall here that many results are also well established. We have not insisted on the historical development of the field, but climatology is based on laws applied with success in mechanics, astronomy, thermodynamics, electromagnetism, chemistry, geology and numerical analysis over decades at least. Studies focussing on important topics such as the impact of changes in greenhouse gases concentrations or the astronomical theory of paleoclimates have their roots in the beginning of the twentieth century or even before [see, e.g., Arrhenius (1896) and the references therein and the discussions in Berger (1988)].