One of the objectives of ClimarisQ is to explain the complexity of climate. Climate is the average weather conditions that prevail over a given region during a long period of time. For the World Meteorological Organization, the reference period must be at least 30 years.
The Climate System: a set of many interconnected layers
The study of climate requires defining the climate system, a complex system consisting of five main components:
- The Atmosphere
- The lithosphere (continental surfaces)
- The hydrosphere (oceans, lakes, rivers, groundwater…)
- The cryosphere (land or sea ice, snow cover)
- The biosphere (all living organisms in the air, on land and in the oceans)
Can we make climate forecasts?
Even simplified, the climate system remains complex (sensitivity to initial conditions, chaotic behavior). Chaotic systems show an exponential sensitivity to small perturbations in the initial conditions. Systems of this type, although governed by deterministic laws, are capable of exhibiting empirical randomness in the evolution of dynamic variables. In 1963, the American meteorologist Edward N. Lorenz modeled atmospheric convection, without turbulence, by three deterministic equations. These allowed him to demonstrate for the first time the butterfly effect, a sign of chaotic behavior illustrated by the question: “Can the flapping of a butterfly’s wing in Brazil trigger a tornado in Texas?”, which appeared in the proceedings of a conference by Lorenz in 1972. Chaos also implies that climate predictions are impossible: we cannot determine what the weather will be like on January 01, 2098.
If it prevents us from making exact climate forecasts, the existence of chaos in the climate allows us to make projections: by looking at the set of possible trajectories for a future date, conditioned on climate scenarios, we can determine the probability of meteorological variables for a given date in the future, for example what will be the probability that the temperature exceeds 15°C on January 01, 2098.
The Greenhouse Effect and Global Warming
In climatology, the term global warming indicates the change in the Earth’s climate that has developed over the course of the 20th century and is still ongoing. This change is largely attributed to the emission of increasing amounts of greenhouse gases into the Earth’s atmosphere (with a consequent increase in the greenhouse effect) and to other factors that the scientific community has identified as attributable to human activity.
During the history of the Earth, there have been several variations in climate that have led the planet to go through different ice ages alternating with warmer periods called interglacial eras. These variations are mainly due to periodic changes in the orbital structure of our planet.</div>In climatology, the term global warming indicates the change in the Earth’s climate that has developed over the course of the 20th century and is still ongoing. This change is largely attributed to the emission of increasing amounts of greenhouse gases into the Earth’s atmosphere (with a consequent increase in the greenhouse effect) and to other factors that the scientific community has identified as attributable to human activity.
There is a natural greenhouse effect and another one caused by artificial causes. The natural one is essential to life on earth because otherwise the temperature would be about 18 degrees below zero: the earth receives solar radiation and the atmosphere and surface of the earth emit in return an infrared radiation that clouds and greenhouse gases (water vapour, carbon dioxide, ozone and methane for the most important ones) absorb and re-emit in large part towards the ground. But since the industrial revolution, human activity has led to an excessive production of CO2 and its concentration has increased massively over the last 150 years. The intensity of the greenhouse effect is now disturbing the balance of the environment. Due to the global rise in temperature, polar ice caps are melting and sea levels are rising, causing unprecedented climate disruption.