4.8. Climate change
The Earth’s climate is constantly changing. It has its natural ‘ups and downs’. In the past, warm and cold periods naturally varied. However, changes that have occurred over the last 100 years, and especially those that follow, are directly under human influence.
Natural causes could be variations in Sun’s radiation, Earth’s Orbit variations (astronomical causes), volcanic eruptions and on the geological time scale even tectonic disturbances. The Sun’s radiation is slightly changing over a longer period of time and these variations have very small impact on the global climate. On the other hand, human climate influence is perceived through various forms of human activity and action. These are, for example, the destructions of forests (deforestation) and increase of agricultural land. Due to the consumption of fossil fuels (in energy, transport, agriculture, etc.) the concentration of carbon dioxide (CO2) and other gases in the atmosphere is constantly increasing and thus affecting the greenhouse effect and consequently global warming.
Current studies are attempting to quantify the consequences of climate change that may occur in the near future: it would seem that the temperature of the globe could be between 1.4 and 5.8 ° C. This alteration is expected to lead to an increase in soil evaporation, accompanied by erosion and salinization, with an advance of desertification and a reduction in the availability of fresh water. An already known evidence is that extreme phenomena such as strong thunderstorms, heavy costal storms, and temperature peaks become more and more important. It is expected that within the years 2025-2030 the greenhouse effect will affect the sea level and a global rise of about 12-18 cm. Most of the Mediterranean coasts will have difficulty sustaining it.
Oceans that absorb almost a third of greenhouse gas emissions in the atmosphere are rapidly becoming acidic for the rise of carbon dioxide in the atmosphere of fossil fuel combustion. Carbon dioxide produces carbonic acid when it is dissolved in seawater and so far has to mitigate the effects of global warming by absorbing almost a third of the carbon dioxide released during the use of fossil fuels. This chemical change could have significant consequences on marine ecosystems and on the goods and services they provide. For example, coastal zones such as the Mediterranean and the North Sea are rich in calcification organisms such as shells that may be particularly vulnerable to major changes in carbon chemistry. Molluscs create their shells by extracting dissolved calcium carbonate from seawater and using it when creating two minerals, calcite and aragonite. Corals use the same process when making their outer skeletons. As the water becomes acidic, the concentration of calcium carbonate falls so that with time there is so little that they can no longer form their shingles and skeletons.