The departure of the Vikings from Scotland in the 13th century coincided with a marked change in Scotland's weather and climate. The period of Medieval warmth was succeeded by a complex change to the colder conditions of the so-called 'Little Ice Age'. Although this period of cold climate is normally associated with deterioration in climate that culminated during the 18th and 19th centuries, we can trace this change to colder conditions as far back as the middle of the 13th century (Lamb 1977).
10.2.1 Changes in solar output
One of the most important climate events that took place over recent centuries is a marked decline in solar radiation between the 17th and 19th century. The most marked decline, represented by a decrease in the number of sunspots on the Sun's surface, is known as the Maunder minimum that culminated between ca. 1640 -1720 AD. The consequences of this sustained decline in solar output on global atmospheric circulation is not known, although it may be surmised with some confidence that a consequence of decreased insolation with an average lowering of global air temperature.
10.2.2 Change in northern hemisphere circulation
Analysis of stable isotopes and the chemistry of Greenland (GISP2) ice cores (Meeker and Mayewski et al. 2002) showed that a marked change in the circulation of the northern hemisphere took place around 1400-1420 AD. The change, represented by increases in the concentration of sea salt sodium and non- sea salt potassium in the ice cores, indicates that after ca. 1420 AD there was a sustained increase in storminess across the North Atlantic region (Na+ ice core chronology) that took place at the same time as a strengthening of the winter Siberian anticyclone (K+ ice core chronology). By contrast, during the Viking era winter storminess was relatively low with higher than average air temperatures and reduced rainfall.
10.2.3 Changes in sea ice cover
Historical records for sea ice cover across the northern North Atlantic region begin with the Icelandic and Greenland sagas with the first indirect evidence for an expanded sea ice cover being the first observations of polar bears in northern Iceland during the 1250s, these requiring passage across sea ice between South East Greenland and North West Iceland. Thereafter, records of sea ice occurrence increase in frequency with the periods of maximum cover having occurred during the 1690s and 1880s. The latter date is significant in the sense of the most extensive cover not having occurred until the last two decades of the 19th century. Indeed, during the winter of 1881-82, sea ice occurred off the coastline of the Faeroe Isles with contemporary observers describing looking out to sea from the hill above Torshavn, the capital, and not being able to see the sea because of the widespread occurrence of sea ice (Lamb 1977). Extensive sea ice cover is also attributed as a key reason why sailing ships could not reach Greenland during much of the 16th -19th century. A change to a greatly diminished sea ice cover, decreased winter storminess and increased air temperatures during the late 1890s and the early 1900s marks the end of the Little Ice Age and the start of 20th century warming.
Just exactly how these changing conditions affected life in Argyll we can only estimate from fragmentary historical records, but Oram and Adderley (2008) and Oram (2014) have discussed possible climatic stresses on upland pastoralism and the links between weather extremes and the introduction of the Black Death (see also Campbell 2016). But there are some clear indicators of what life was like. We know that the exceptional cold of many periods of the Little Ice Age was associated with increased snowfall. Indeed, the many snowdrifts faced by representatives of the MacDonalds in trying to reach Inverary on time during that fateful winter at the end of the 17th century set a chain of events in motion that led to the Massacre of Glencoe. From what we can tell from documentary records, periods of prolonged snow cover appear to have been a characteristic of the 18th century compared to the 19th century which was stormier and wetter. During lengthy periods of the 18th century, Scotland was affected many times by cold East, North East and North air flow during winter. When snow had fallen, it tended to stay on the ground for long periods, for example during the 1740s, 1770s and 1780s. As a result, ploughing of ground often occurred late into spring (sometimes as late as April or even May) with harvests and planting often interrupted by an early start of winter. By contrast, much of the 19th century appears to have been dominated by more tempestuous weather. Summer storms were not uncommon while winters were characterised by sequences of cyclones coming in from the Atlantic.
It has long been argued that a more extensive cover of sea ice during the Little Ice Age led to a steeper meridional (north-south) temperature gradient across the North Atlantic and thereby more intense and more frequent winter storms (see above). With the storms came much greater rainfall (together with snowfall) with damaging consequences for crop growth and the cutting of peat for winter fuel. Wet summers and autumns, together with increased rainfall during summer is known to have damaged crops of oats and bere (the early form of barley), as well as ruining potato crops and making peat too wet to be cut for fuel. Consideration of all of these impacts on land use makes it very clear that crofters and cottars across the Highlands and Islands endured great hardship throughout most of the period between the 1500s through to the late 1800s. If one adds political and social turmoil linked to oppressive landlords and tacksmen, one can easily understand why this period of Scottish history is associated with such high levels of emigration (both forced and voluntary) to the New World.
A side-effect of the cold conditions characteristic of the 17th - 19th centuries was decreased ocean temperatures. This had the effect of changing fisheries with numerous species migrating southward in response to decreased ocean temperatures. Perhaps the greatest visible change was the arrival of shoals of herring and it is no coincidence that the boom in herring fishing took place throughout the 19th century when ocean temperatures were low. One may infer from this that during the 17th-19th century, that coastal communities in Argyll found plenty of fish to eat but found it difficult to crop potatoes, oats and barley. The history of the Highlands and Islands for the 17-19th century is punctuated by years of dearth and famine. Particularly severe were the dearths and famines of the 1620s, the 1690s (known infamously as the 'Dear Years of King William') and the 1780s. These and other times of hardship made life for ordinary working folk almost unbearable.