The climate of France is the statistical distribution of conditions in the Earth's atmosphere over the national territory, based on the averages and variability of relevant quantities over a given period, the standard reference period defined by the World Meteorological Organization being 30 years. Climate characterization is based on annual and monthly statistical measurements of local atmospheric data: temperature, atmospheric pressure, precipitation, sunshine, humidity, wind speed. Recurrence and exceptional events are also taken into account.
Located between latitudes 41° 19' N and 51° 04'N, metropolitan France is currently in the temperate zone, characterized by warm summers and moderately cold winters. This classification distinguishes between oceanic (cool summers, mild winters, high precipitation), continental (hot summers, cold winters, low precipitation), Mediterranean (hot, dry summers, mild winters, autumn precipitation), mountain (colder and wetter than the surrounding plains) and altered oceanic (a transition zone between oceanic and mountain climates and semi-continental climate). Extreme temperatures recorded in mainland France are 46.0 °C in Vérargues on 28 June 2019 and −36.7 °C in Mouthe on 13 January 1968.
The climates of France's overseas territories are many and varied, depending on their position on the globe, ranging from the cold oceanic type for the subantarctic islands, to the tropical maritime type for the French West Indies, the equatorial type for French Guiana and the polar maritime type for Saint-Pierre-et-Miquelon. French Polynesia, which extends over 20 degrees of latitude, is divided into 5 types.
These climates have varied greatly in the past, with warm periods (optimums) and cold periods (ice ages). Paleoclimates, which date back to geological times, have been marked by alternating ice ages (around 80,000 years) and warm periods (around 20,000 years) at intervals of around 100,000 years. The last Ice Age was a period of global cooling, or glaciation, which marked the end of the Pleistocene on the entire planet. It began 115,000 years ago and ended 11,700 years ago, when the Holocene, the current interglacial period, began. The latter is characterized by the Roman climatic optimum (−300 to +200), the Medieval climatic optimum (900–1300) and the Little Ice Age (1300–1860). The contemporary period (1860 to the present) is marked by the end of the Alpine Little Ice Age (1860-1900-1910), followed by the onset of global warming.
The IPCC's sixth assessment report confirms with certainty the anthropization origin of the global warming already observed. Temperatures in mainland France today are 1.66 °C higher than those measured between 1900 and 1930, with 1.63 °C attributable solely to human activity. Analysis of more precise temperature data between 2010 and 2019 shows that, over this short period, France is warming by 0.1 °C every 3 years. To meet the two objectives of the Paris climate agreement (warming well below 2 °C and preferably limited to 1.5 °C), a sharp and immediate reduction in CO2 emissions is essential, until we reach carbon neutrality, the only way to halt global warming. Reducing emissions of other greenhouse gases, particularly methane, is also relevant. To meet this objective, France, through its climate policy, is deploying various mitigation and adaptation strategies, with specific targets such as reducing greenhouse gas emissions by 40% between 1990 and 2030 (20% in 2019) or reducing final energy consumption by 50% in 2050 compared with the 2012 baseline, with an intermediate target of 20% in 2030.
Notion of climate The notion of climate has evolved considerably, and it's now easier to define what the "climate system" is, i.e. all the very different components that make up the atmosphere, the oceans, the continental surface, and all their physical, chemical and biological interactions. The word "climate" thus goes beyond the usual strictly atmospheric definition to designate the characteristics of the climate system in a given place, characteristics established over a period, often 30 years, known as the Climate Norm. The parameters used to describe a region's climate are many and varied, from temperature, wind and air humidity to soil water content, river conditions, atmospheric composition and ocean salinity. They are most often analyzed in terms of annual, monthly or seasonal averages. But characterizing climate also means describing rarer and more irregular events, such as violent storms or persistent drought.
France is a transcontinental sovereign state whose metropolitan territory extends across Western Europe, and whose overseas territories stretch across the Indian, Atlantic and Pacific oceans, as well as Antarctica and South America. It is thus characterized by a wide variety of climates, which have also been highly variable over time.
Paleoclimates
Milanković cycles
Life appeared on Earth between 3.8 and 3.5 billion years ago, in the form of the first cells. It was the first living organisms capable of recovering carbon from atmospheric CO2 dissolved in water and progressively enriching the atmosphere with oxygen (photosynthesis) that set in motion the dynamic cycle of water and climate. The first hominids appeared around 4 million years ago. Ice core records provide a good understanding of the climate over the last million years. It is marked by alternating ice ages (around 80,000 years) and warm periods (around 20,000 years) with a periodicity of around 100,000 years. Since the appearance of man, the average temperature at the Earth's surface has been relatively constant, varying by only a few degrees from an average of around 15 °C.
The regular alternation of warm and cold periods can be explained by astronomy. In 1924, Serbian geophysicist Milutin Milanković demonstrated that three independent parameters characterize the Earth's orbit around the sun and modulate the amount of solar energy according to the seasons: eccentricity, obliquity, the inclination of the Earth's axis of rotation on itself in relation to the plane of rotation around the sun (currently close to 23°) and climatic precession, a term defining variations in the Earth's axis of rotation. Each of these parameters varies over time with independent periods, and their conjunction makes the construction, or disappearance, of icecaps in the Northern Hemisphere more or less favorable, and these icecaps play a decisive role in climate. In France, the South-East basin, considered part of the Alpine domain, stands out from other French geological basins for the very great thickness of its sedimentary layer. Alternating marl and limestone deposits are particularly well exposed in the Vocontian Basin, where Lower Cretaceous formations are mostly in the form of alternating limestone banks and marl interbanks. These alternating sedimentary successions perfectly reflect the interlocking Milanković cycles, providing one of the best proofs of astroclimatic control of sedimentation.
Last Ice Age (−115,000 to −11,700 years ago)
Last Ice Age (−115,000 to −19,000 years ago) The Last Ice Age is a period of global cooling, or glaciation, that marks the end of the Pleistocene on the entire planet. It began 115,000 years ago and ended 11,700 years ago, when the Holocene began.
Abrupt changes of millennial cyclicity punctuated this last glacial period and had a strong impact on terrestrial and marine ecosystems, as well as on atmospheric composition and temperature. Periods characterized by rising water temperatures in the North Atlantic, Greenland and greenhouse gas concentrations were contemporary with the development of forest in Europe below 50°N, and alternated with cold periods of steppe vegetation. During the changes observed around 40,000 years before present, Neanderthal man disappeared and modern man colonized Europe.
These changes, known as the Dansgaard-Oeschger cycles after their discoverers, have given rise to some forty very rapid climatic pulsations. These phases are associated with variations in North Atlantic surface water temperature and changes in climate on the European continent. These pulses lasted for several millennia, and the transition from a cold episode (stage) to a temperate episode (interstage) seems to have been very rapid, on the order of a few decades, sometimes less! Some of these cold episodes were accompanied by a massive influx of icebergs into the Bay of Biscay from the ice cap covering Canada. These iceberg break-ups, known as Heinrich events, were brutal: each would have lasted on the order of a century, or even a few millennia. Studies of Bay of Biscay sediments have shown that each Heinrich event is synchronous with the rapid development (< 100 years) of a "Central European-type" grass steppe at the expense of pine forest.
The glacial maximum was reached around 21,000 years ago. One of the consequences of this cooling was a marine regression (a general drop in sea level) of around 120 meters at its maximum, and the establishment of a periglacial climate in Europe, North Asia and North America, leading to profound changes in flora and fauna. At the time of this glacial maximum, the Arctic ice cap covered northern Europe, the glaciers of the Alps descended as far as Lyon, and those of the Pyrenees as far as Arudy (Pyrénées-Atlantiques). Sea level was around 120 m below present, and the shoreline was pushed ~50 km offshore. In southern Aquitaine, deglaciation of the high Pyrenean mountains must have ended around 15,000 years ago. During the last glacial episode, the Landes was a vast sandy expanse dotted with 'fields of small crescent-shaped dunes of metric height. Beyond the Garonne to the east and the Adour to the south, finer particles (loess) carried by storms to higher altitudes were deposited to form accumulations on the relief, where steppe vegetation then developed.
Tardiglacial (−19,000 to −11,700 years ago)
The Tardiglacial is the period between the Last Glacial Maximum, which ended around 19,000 years ago, and the beginning of the Holocene, 11,700 years ago, during which there was an irregular rise in temperatures, interspersed with relapses. The beginning of the Tardiglacial period in Europe was marked by the disappearance from our latitudes of certain "archaic" animal species (mammoths, woolly rhinoceroses, cave bears). Reindeer and horses (Equus caballus gallicus), sometimes combined with Bovinae (bison or aurochs), became the dominant species of the early Interstadial period, judging by the hunting records of human societies.
The Alleröd (13,900 to 12,900 years ago) is characterized by an increase in tree cover. In the Paris Basin and in Belgium, pollen analyses enable us to distinguish two phases in this episode: the first is characterized by the establishment of an open birch forest (afforestation rate of around 45%); the second, which may be separated by a slight retreat in tree cover, sees the expansion of an open pine-dominated forest. Arctic species are partly replaced by woodland species: aurochs and horses – occasionally present – are joined by deer, roe deer, wild boar, elk and beaver.
Cave paintings can also provide clues to the climate, but these must be interpreted with care. Plants are rare in cavern art, but the animals depicted can help us to understand the climate outside, even if the species depicted on the cave walls represent only a selection. The compositions do not constitute a photograph of the external landscape. The presence of a saiga antelope on a wall in Rouffignac (Dordogne) betrays cold, dry steppe conditions. The fact that there is only one reindeer and no mammoth depicted at Lascaux may indicate milder temperatures (or perhaps the artists weren't interested in these animals).