Academic literature on the topic 'Bright sunshine hour'

This chapter gives a description of the main characteristics of present-day climate. In describing the mean state and its variability, attention is also given to the underlying causes. For comparison, there is a short summary of early European climate, from the last glacial maximum, through the Holocene and up to the Little Ice Age (the period AD 1400–1850). The chapter finishes with a comprehensive section on climate change, with emphasis on the anthropogenic causes of recent changes. The climate of western Europe has a maritime character. The weather mainly originates from the North Atlantic Ocean and its neighbouring seas. Further inland, in what is usually called central Europe, climate changes to a more continental type, but certain maritime features are still present. It is therefore called an altered maritime climate. Only in the most southern part, southern France for instance, is the Atlantic character lost and several new features are present. These features are characteristic of a Mediterranean climate. Climates may be called cold or warm, dry or wet, gloomy or sunny, depending on the prevailing temperatures, amount and frequency of precipitation, and the number of hours of bright sunshine. Such terms, however, are not objective unless certain, generally accepted, reference values are used. In the past different sets of reference values were proposed, each of them defining a system of climatic types. A well-known classification system was the one developed by Köppen (1936). The Köppen system distinguished eleven main climate types, based on well-defined temperature and precipitation characteristics. These were mainly referring to the response of vegetation, natural as well as cultivated, to climatic conditions. The eleven Köppen climates are indicated by the letters A–E, with some subdivision, using other letters. In the Köppen classification the whole of western Europe has a Cf climate, which means a moist, temperate climate, without a specific dry season. Cf climates occupy 22% of the globe (oceans included). A second method to describe climate is by using the well-known definition of climate as being the average weather conditions in a certain area, over a given period of time. In practice, however, there is no direct information about weather conditions.