The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present, after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene together form the Quaternary period. The Holocene has been identified with the current warm period, known as MIS 1. It is considered by some to be an interglacial period within the Pleistocene Epoch, called the Flandrian interglacial.
The Younger Dryas was a return to glacial conditions which temporarily reversed the gradual climatic warming after the Last Glacial Maximum. The Younger Dryas was the last stage of the Pleistocene epoch and it preceded the current, warmer Holocene epoch. The Younger Dryas was the most severe and long lasting of several interruptions to the warming of the Earth's climate, and it was preceded by the Late Glacial Interstadial.
The Last Glacial Period (LGP), also known colloquially as the last ice age or simply ice age, occurred from the end of the Eemian to the end of the Younger Dryas, encompassing the period c. 115,000 – c. 11,700 years ago. The LGP is part of a larger sequence of glacial and interglacial periods known as the Quaternary glaciation which started around 2,588,000 years ago and is ongoing. The definition of the Quaternary as beginning 2.58 million years ago (Mya) is based on the formation of the Arctic ice cap. The Antarctic ice sheet began to form earlier, at about 34 Mya, in the mid-Cenozoic. The term Late Cenozoic Ice Age is used to include this early phase. The previous ice age, the Saalian glaciation, which ended about 128,000 years ago, was more severe than the Last Glacial Period in some areas such as Britain, but less severe in others.
Before Present (BP) years, or "years before present", is a time scale used mainly in archaeology, geology and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Because the "present" time changes, standard practice is to use 1 January 1950 as the commencement date (epoch) of the age scale. The abbreviation "BP" has been interpreted retrospectively as "Before Physics", which refers to the time before nuclear weapons testing artificially altered the proportion of the carbon isotopes in the atmosphere, which scientists must now account for.
The Holocene Climate Optimum (HCO) was a warm period that occurred in the interval roughly 9,000 to 5,000 years ago BP, with a thermal maximum around 8000 years BP. It has also been known by many other names, such as Altithermal, Climatic Optimum, Holocene Megathermal, Holocene Optimum, Holocene Thermal Maximum, Hypsithermal, and Mid-Holocene Warm Period.
During the Last Glacial Maximum, the mammoth steppe, also known as steppe-tundra, was the Earth's most extensive biome. It spanned from Spain eastward across Eurasia to Canada and from the arctic islands southward to China. The mammoth steppe was cold and dry. The vegetation was dominated by palatable high-productivity grasses, herbs and willow shrubs. The animal biomass was dominated by reindeer, bison, horses, and woolly mammoth. This ecosystem covered wide areas of the northern part of the globe, thrived for approximately 100,000 years without major changes, but then diminished to small regions around 12,000 years ago.
Tephrochronology is a geochronological technique that uses discrete layers of tephra—volcanic ash from a single eruption—to create a chronological framework in which paleoenvironmental or archaeological records can be placed. Such an established event provides a "tephra horizon". The premise of the technique is that each volcanic event produces ash with a unique chemical "fingerprint" that allows the deposit to be identified across the area affected by fallout. Thus, once the volcanic event has been independently dated, the tephra horizon will act as time marker.
The Holocene glacial retreat is a geographical phenomenon that involved the global retreat of glaciers (deglaciation) that previously had advanced during the Last Glacial Maximum. Ice sheet retreat initiated ca. 19,000 years ago and accelerated after ca. 15,000 years ago. The Holocene, starting with abrupt warming 11,700 years ago, resulted in rapid melting of the remaining ice sheets of North America and Europe.
The 4.2-kiloyear BP aridification event was one of the most severe climatic events of the Holocene epoch. It defines the beginning of the current Meghalayan age in the Holocene epoch.
The neoglaciation describes the documented cooling trend in the Earth's climate during the Holocene, following the retreat of the Wisconsin glaciation, the most recent glacial period. Neoglaciation has followed the hypsithermal or Holocene Climatic Optimum, the warmest point in the Earth's climate during the current interglacial stage, excluding the global warming-induced temperature increase starting in the 20th century. The neoglaciation has no well-marked universal beginning: local conditions and ecological inertia affected the onset of detectably cooler conditions.
Quaternary science is the study which represents the systematic study of the Quaternary Period commonly known as the ice age. The Quaternary Period is a time period that started around 2.58 million years ago and continues today. This period is divided into two epochs – the Pleistocene Epoch and the Holocene Epoch. The aim of Quaternary science is to understand everything that happened during the Pleistocene Epoch and the Holocene Epoch to be able to acquire fundamental knowledge about Earth's environment, ecosystem, climate changes, etc. Quaternary science was first studied during the nineteenth century by Georges Cuvier, a French scientist. Most Quaternary scientists have studied the history of the Quaternary to predict future changes in climate.
In climatology, the so-called "8.2-kiloyear event" was a sudden decrease in global temperatures that occurred approximately 8,200 years before the present (BP), that is, c. 6,251 BC. It defines the start of the Northgrippian age in the Holocene epoch. Milder than the Younger Dryas cold period before it but more severe than the Little Ice Age after it, the 8.2-kiloyear cooling was a significant exception to general trends of the Holocene climatic optimum. During the event, atmospheric methane concentration decreased by 80 ppb, an emission reduction of 15%, by cooling and drying at a hemispheric scale.
The Piora Oscillation was an abrupt cold and wet period in the climate history of the Holocene Epoch; it is roughly dated to c. 3900-3000 BC. Some researchers associate the Piora Oscillation with the end of the Atlantic climate regime, and the start of the Sub-Boreal, in the Blytt–Sernander sequence of Holocene climates.
Bond events are North Atlantic ice rafting events that are tentatively linked to climate fluctuations in the Holocene. Eight such events have been identified. Bond events were previously believed to exhibit a roughly c. 1,500-year cycle, but the primary period of variability is now put at c. 1,000 years.
The Subboreal is a climatic period, immediately before the present one, of the Holocene. It lasted from 3710 to 450 BCE.
The Subatlantic is the current climatic age of the Holocene epoch. It started about 2,500 years BP and is still ongoing. Its average temperatures are slightly lower than during the preceding Subboreal and Atlantic. During its course, the temperature underwent several oscillations, which had a strong influence on fauna and flora and thus indirectly on the evolution of human civilizations. With intensifying industrialisation, human society started to stress the natural climatic cycles with increased greenhouse gas emissions.
The Hekla 3 eruption (H-3) circa 1000 BC is considered the most severe eruption of Hekla during the Holocene. It threw about 7.3 km3 of volcanic rock into the atmosphere, placing its Volcanic Explosivity Index (VEI) at 5. This would have caused a volcanic winter, cooling temperatures in the Northern Hemisphere for several years afterwards.
The Roman Warm Period, or Roman Climatic Optimum, was a period of unusually-warm weather in Europe and the North Atlantic that ran from approximately 250 BC to AD 400. Theophrastus wrote that date trees could grow in Greece if they were planted but that they could not set fruit there. That is still the case today, which implies that South Aegean mean summer temperatures in the 4th and the 5th centuries BC were within a degree of modern ones. That and other literary fragments from the time confirm that the Greek climate was basically the same then as around 2000. Tree rings from the Italian Peninsula in the late 3rd century BC indicate a time of mild conditions there around the time of Hannibal's crossing of the Alps with imported elephants in 218 BC.
Siwan Davies is a Welsh professor of Physical Geography in the department of science at Swansea University.
The Homeric Minimum is a grand solar minimum that took place between 2,800 and 2,550 years Before Present. It appears to coincide with, and have been the cause of, a phase of climate change at that time, which involved a wetter Western Europe and drier eastern Europe. This had far-reaching effects on human civilization, some of which may be recorded in Greek mythology and the Old Testament.
