Little Ice Age in the context of "Crisis of the Late Middle Ages"

The Medieval Warm Period (MWP), also known as the Medieval Climate Optimum or the Medieval Climatic Anomaly, was a time of warm climate in the North Atlantic region that lasted from about 950 CE to about 1250 CE. Climate proxy records show peak warmth occurred at different times for different regions, which indicate that the MWP was not a globally uniform event. Some refer to the MWP as the Medieval Climatic Anomaly to emphasize that climatic effects other than temperature were also important.

The MWP was followed by a regionally cooler period in the North Atlantic and elsewhere, which is sometimes called the Little Ice Age (LIA).

The Crisis of the Late Middle Ages was a series of events across Europe during the late Middle Ages. These events involved extensive demographic collapse, political instability, and religious upheaval. Collectively, they marked an end to a centuries-long period of relative stability in Europe, and reshaped regional societies. This crisis period coincides with a shift in the regional climate from the Medieval Warm Period to the Little Ice Age.

The events of the Crisis include the Great Famine of 1315–1317 and the Black Death of 1347–1351, which caused very high mortality across the region. Population did not rise to pre-crisis levels until around 1500.

An alpine lake is a high-altitude lake in a mountainous area, usually near or above the tree line, with extended periods of ice cover. These lakes are commonly glacial lakes formed from glacial activity (either current or in the past) but can also be formed from geological processes such as volcanic activity (volcanogenic lakes) or landslides (barrier lakes). Many alpine lakes that are fed from glacial meltwater have the characteristic bright turquoise green color as a result of glacial flour, suspended minerals derived from a glacier scouring the bedrock. When active glaciers are not supplying water to the lake, such as a majority of Rocky Mountains alpine lakes in the United States, the lakes may still be bright blue due to the lack of algal growth resulting from cold temperatures, lack of nutrient run-off from surrounding land, and lack of sediment input. The coloration and mountain locations of alpine lakes attract lots of recreational activity.

Alpine lakes are some of the most abundant types of lakes on Earth. In the Swiss Alps alone, there are nearly 1,000 alpine lakes, most of which formed after the Little Ice Age. As global temperatures continue to rise, more alpine lakes will be formed as glaciers recede and provide more run-off to surrounding areas, and existing lakes will see more biogeochemical changes and ecosystem shifts. An alpine lake's trophic state (i.e., level of biological productivity) progresses with age (e.g., low productivity after formation and increased productivity with vegetation and soil maturity in the surrounding watershed), but anthropogenic effects such as agriculture and climate change are rapidly affecting productivity levels in some lakes. These lakes are sensitive ecosystems and are particularly vulnerable to climate change due to the highly pronounced changes to ice and snow cover. Due to the importance of alpine lakes as sources of freshwater for agricultural and human use, the physical, chemical, and biological responses to climate change are being extensively studied.

The history of Greenland is a history of life under extreme Arctic conditions: currently, an ice sheet covers about eighty percent of the island, restricting human activity largely to the coasts. The first humans are thought to have arrived in Greenland around 2500 BCE. Their descendants most likely died out and were replaced and succeeded by several other human groups migrating from continental North America since then. There has been no evidence discovered that Greenland was known to Norsemen until the 9th century CE, when Norse Icelandic explorers settled on its southwestern coast. The ancestors of the Greenlandic Inuit who live there today appear to have migrated there later, around the year 1200, across the Nares Strait from northern Canada.

While Inuit survived in the icy world of the Little Ice Age, the early Norse settlements, known as the Eastern Settlement, along the southwestern coast disappeared, leaving Inuit as the only inhabitants of the island for several centuries. During this time, Denmark–Norway, apparently believing the Norse settlements had survived, continued to claim sovereignty over the island despite the lack of any contact between the Norsemen (specifically Icelanders) installed in Greenland and their Scandinavian brethren. In 1721, aspiring to become a colonial power, Denmark-Norway sent a missionary expedition to Greenland with the stated aim of reinstating Christianity among descendants of the Norse Greenlanders who may have converted back to paganism. When the missionaries found no descendants of the Norse Greenlanders, they baptised the Inuit they found living there instead. Denmark-Norway then developed trading colonies along the coast and imposed a trade monopoly and other colonial privileges on the area.

Patterns of solar irradiance and solar variation have been a main driver of climate change over the millions to billions of years of the geologic time scale.

Evidence that this is the case comes from analysis on many timescales and from many sources, including: direct observations; composites from baskets of different proxy observations; and numerical climate models. On millennial timescales, paleoclimate indicators have been compared to cosmogenic isotope abundances as the latter are a proxy for solar activity. These have also been used on century times scales but, in addition, instrumental data are increasingly available (mainly telescopic observations of sunspots and thermometer measurements of air temperature) and show that, for example, the temperature fluctuations do not match the solar activity variations and that the commonly-invoked association of the Little Ice Age with the Maunder minimum is far too simplistic as, although solar variations may have played a minor role, a much bigger factor is known to be Little Ice Age volcanism. In recent decades observations of unprecedented accuracy, sensitivity and scope (of both solar activity and terrestrial climate) have become available from spacecraft and show unequivocally that recent global warming is not caused by changes in the Sun.

François Émile Matthes ((1874-03-16)March 16, 1874 – (1948-06-21)June 21, 1948) was a geologist and an expert in topographic mapping, glaciers, and climate change. He mapped remote areas of the American West for the United States Geological Survey (USGS). His maps coincided with the development of those areas into national parks. He is one of the founders of the Association of American Geographers and served as its president. Matthes resolved a dispute about formation of the Yosemite Valley and his findings on glaciers introduced the terms nivation and Little Ice Age.

Little Ice Age volcanism refers to the massive volcanic activities during the Little Ice Age. Scientists suggested a hypothesis that volcanism was the major driving force of the global cooling among the other natural factors, i.e. the sunspot activities by orbital forcing and greenhouse gas. The Past Global Change (PAGES), a registered paleo-science association for scientific research and networking on past global changes in the University of Bern, Switzerland, suggested that from 1630 to 1850, a total of 16 major eruptions and cooling events had taken place. When a volcano erupts, ashes burst out of the vent together with magma and forms a cloud in the atmosphere. The ashes act as an isolating layer that block out a proportion of solar radiation, causing global cooling. The global cooling effect impacts ocean currents, atmospheric circulation and cause social impacts such as drought and famine. Wars and rebellions were therefore triggered worldwide in the Little Ice Age. It was suggested that the crisis on Ottoman Empire and Ming-Qing Transition in China were typical examples that closely correlated with Little Ice Age.

Grinnell Glacier is in the heart of Glacier National Park in the U.S. state of Montana. The glacier is named for George Bird Grinnell, an early American conservationist and explorer, who was also a strong advocate of ensuring the creation of Glacier National Park. The glacier is in the Lewis Range and rests on the north flank of Mount Gould at an altitude averaging 7,000 feet (2,100 m), in the Many Glacier region of the park.

The glacier has been one of the most photographed glaciers in the park and many of these photographs date back to the mid 19th century during the late Little Ice Age. When compared with images taken over subsequent years, the glacier has obviously retreated substantially. In 1850, Grinnell Glacier measured 710 acres (2.9 km), including the area of Salamander Glacier, an ice apron or shelf glacier that used to be attached to Grinnell, but is now separate. By 1993, Grinnell Glacier measured 220 acres (0.89 km) and The Salamander measured 57 acres (0.23 km).