Climate change: causes and medium range perspectives.

Meteorology and climatology are disciplines which have been studied foa a long time ago in different epochs and societies. Meteorological data have been collected, either systematically or sporadically, over the course of history by different scientists or amateurs of several civilizations such as Egyptians, Indians, Babylonian, Chinese, Greeks and Romans and, later, by intellectuals and academics in Europe during the Middle Age and the Renaissance. However it is only in the last few decades that climatology and meteorology started to be considered as sciences rather than ancillary disciplines. During the first half of the 20th century, climatologists studied the distribution of different climates and analyzed physical, biological, economic and agricultural aspects related to the climate in order to classify climatologically homogeneous regions. TheWorld Meteorological Organization (WMO) was established after World War II in 1951, and only in the second half of the last century data have been systematically collected and analyzed and observation networks set up. Despite the fact that meteorology and the improvement of meteorological forecasts were the main concern, during this period scientists began systematic analysis of the climate of the past eras and of its recent variability. It was also at this time that the hypothesis of recent climate change is partly due to human activities, although this has not yet been fully accepted by the whole scientific community, started to be investigated in order to determine what the human contribution is to climatic change, and what is the result of natural causes.. In this perspective great efforts are currently being spent in order to investigate the main causes of climate change and variability, and the impact of climate change on several areas, namely ecosystems, human health, agriculture, water resources, etc., and finally possible adaptation and mitigation strategies to be adopted.