TheLate Antique Little Ice Age (LALIA) was a long-lastingNorthern Hemispheric cooling period in the 6th and 7th centuries AD, during the period known asLate Antiquity. The period coincides with threelarge volcanic eruptions in 535/536, 539/540 and 547. Thevolcanic winter of 536 was the early phenomenon of the century-long global temperature decline. One study suggested a global cooling of 2 °C (3.6 °F).[2] The period contributed to the decline of theRoman Empire and influenced thesecond wave migration period, primarily of theearly Slavs.
The term and concept were first coined and described in February 2016, in theNature Geoscience article titled "Cooling and societal change during the Late Antique Little Ice Age from 536 to around 660 AD" by Ulf Büntgen, et al.[3]
The existence of a cooling period was proposed as a theory in 2015, and subsequently confirmed as the period from AD 536 to about 660.[3] Volcanic eruptions, meteorites striking the Earth's surface, and comet fragments exploding in the upper atmosphere have been proposed for the climatic cooling in 536 and afterwards. A problem is that no impact crater for a meteorite has been found, even though the land area and sea beds have been well surveyed for evidence. A comet fragment half a kilometer in size exploding in the atmosphere could cause a plume of debris on the Earth and create conditions for atmospheric cooling.[4] Most evidence, however, points to volcanic eruptions occurring in 536, 540, and possibly 547, although the location of the volcano or volcanoes has not been determined. Locations such asTavurvur inPapua New Guinea,Ilopango inEl Salvador, andKrakatau inIndonesia have been proposed.[5]
Investigations in 2018 analyzedice cores from glaciers in Switzerland and matched glass particles in the cores with volcanic rocks fromIceland, making the island nation a likely candidate for the source of the 536 eruption, although North America is also a possible location.[6] Evidence suggests that Ilopango in El Salvador was the source of the 539/540 eruption. Bipolar ice core investigations suggested that this eruption occurred in the tropics, andtree ring investigations near Ilopango found evidence of an eruption possibly in 540. However, a more recent study, examining other evidence, dated the eruption of Ilopango to 431, so the issue remains unresolved.[2][7] The eruption, whatever its location, put more aerosols into the atmosphere than the1815 eruption of Mount Tambora, which caused theYear Without a Summer.[8] Another eruption, location unknown, occurred in 547.[6] Additional evidence comes from a temperature reconstruction from the Euro-Med2k working group of the international PAGES (Past Global Changes) project that used new tree-ring measurements from theAltai Mountains, which closely matches the temperatures in theAlps in the last two centuries.[3][9]
The impact of the volcanic eruptions was the phenomenon known asvolcanic winter. In thevolcanic winter of 536, summer temperatures fell by as much as 2.5 degrees Celsius (4.5 degrees Fahrenheit) below normal in Europe. ("Normal" is considered by scientists to be the average temperatures of the 1961–1990 period.) The lingering impact of the volcanic winter of 536 was augmented in 539–540, when the second volcanic eruption caused summer temperatures to decline as much as 2.7 degrees Celsius (4.9 degrees Fahrenheit) below normal in Europe.[10]
While the volcanic eruptions began the freeze, researchers think that increased oceanice cover (feedback to the effects of the volcanoes), coupled with an "exceptional" minimum of solar activity in the 600s, reinforced and extended the cooling.[11][12]
According to research by a team from theSwiss Federal Research Institute atBirmensdorf, the fall in temperatures led to theArabian Peninsula experiencing a dramatic increase in fertility.[12] The boost of food supply contributed to the Arab expansion beyond the peninsula in theIslamic conquests. The cooling period also led to increased strain on theEastern Roman Empire and theSassanid Empire, which helped theMuslim conquest of the Levant, theMuslim conquest of Egypt and theMuslim conquest of Persia.[3]
According to research done by Israeli scientists, in 540, the size of the population of the city ofElusa, in theNegev Desert, and the amount of garbage that it generated started to shrink greatly.[13] Elusa housed tens of thousands of people during its height.[13] The major decline took place around the mid-6th century, about a century before the Islamic conquest.[14] One possible explanation for the crisis was the Late Antique Little Ice Age.
The cooling period likely devastated Northern Europe leading to as many as half of the population in for example Scandinavia perishing, and has been credited as being the real precedent to the concept in Norse mythology referred to asFimbulwinter.[15]
The cooling period coincided with thePlague of Justinian, which began in 541, though the connection between the plague and the volcanoes still remains tenuous.The cooling period contributed to the migrations of theLombards and theSlavs into Roman territory in Italy and the Balkans.[3]
According to 2024 research, major plagues that significantly impacted the remnants of the Roman Empire, during the Late Antique Ice Age, are strongly linked to cooler and drier climate conditions, indicating that colder weather may have contributed to the spread of these diseases during that time. It is thought climate stress interacted with social and biological variables, such as food availability, rodent populations, and human migration, making populations more susceptible to disease.[16][17] On the other hand, Haggai Olshanetsky and Lev Cosijns argue that the plague and LALIA had a limited impact, as various archaeological evidence indicates there was no demographic or economic decline in the 6th century eastern Mediterranean.[18]
It may have caused political upheavals in China.[3]
The researchers suggest that the spate of eruptions combined with a solar minimum, and ocean and sea-ice responses to the effects of the volcanoes
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