Professor Antonio Navarra held the second lesson at the fourth edition of the Siena International School on Sustainable Development. Here are some of the key points to remember:
- Crucial experiments such as the Michelson–Morley experiment are not applicable to climate science. Nevertheless, the climate system can be represented via a set of mathematical relations, namely, the equation of climate, which enables the experiments. Although the equation of climate is difficult to solve, numerical approaches can ease the process. Complex mathematical equations can then be treated at the cost of a large number of elementary operations.
- It is crucial to investigate the ability of general circulation models (GCMs) to simulate extreme events and to understand the impact of climate change on their distribution, frequency, and location.
- Why should we care about the climate? It is not only about the economic costs. An extreme climate event can have an impact on human activities, resulting in direct and indirect damage.
- Specific impacts, hazards, and/or vulnerabilities are observed at some individual case-study locations, such as the Mediterranean region as a whole. Some impacts, such as heat stress and flooding, have clear and direct links to climate events, whereas others, such as energy supply and demand, have more indirect causal relationships, involving a cascade of climate, social, and economic influences.
- All case studies, including irrigation capacity and growing season length in agricultural regions, as well as saltwater intrusion into aquifers, show that water availability and severe temperatures are common drivers of current climate impacts.
- Human influence has warmed the climate at an unprecedented rate in at least the last 2000 years. The increasing average temperature of the Planet depends on our choices. What we can do is mitigation, i.e. removing the causes of climate change such as emissions, and adaptation, i.e. preparing for the coming climate change.
- How can science help? By doing experiments on the entire Earth system to enable study of the climate. First of all, building a virtual Earth and then being able to conduct experiments that, without models and simulations, would never have been feasible. As a result, the study of the climate begins with a better understanding of its changes and the discovery of their geopolitical, environmental, social, and economic implications.
- Statistical methods, numerical simulations, and simplified models are used to investigate the dynamic mechanisms that regulate climate variability on a global scale, with a focus on the atmosphere-ocean system. The simulation and assessment of climate change using future climate scenarios is also covered with them.
- The representations of climate change illustrated by the IPCC reports allow a mathematical simulation of climate change using progressively smaller cells which enable ever greater precision. Also, they highlight that the increase in CO2 involves an increase in temperatures and a shift of the precipitation bands towards the North, with a decrease in rainfall in the Mediterranean area.
