The Little Ice Age (LIA) was a time when temperatures were cooler in certain areas, especially in the North Atlantic region. It was not a true ice age that covered the entire world. The term "Little Ice Age" was first used in scientific writing by François E. Matthes in 1939. Scientists usually say the LIA lasted from the 16th to the 19th centuries, but some experts believe it started around 1300 and ended around 1850.
According to NASA Earth Observatory, there were three major cold periods during the LIA. The first began around 1650, the second around 1770, and the third around 1850. These cold times were separated by short periods when temperatures slightly increased. The Intergovernmental Panel on Climate Change’s Third Assessment Report noted that the timing and areas affected by the LIA suggest that climate changes happened independently in different regions, not as a single global event. At most, the Northern Hemisphere experienced only small cooling during this time.
Scientists have suggested several possible causes for the LIA. These include times when the sun’s energy was lower, increased volcanic activity, changes in ocean currents, shifts in Earth’s orbit and tilt, natural climate changes, and decreases in human populations due to events like the Black Death, epidemics in the Americas after European contact, and other historical conflicts.
Areas involved
The Intergovernmental Panel on Climate Change Third Assessment Report (TAR) of 2001 described the areas affected by climate changes:
Evidence from mountain glaciers suggests that glaciers grew in several regions outside Europe before the 20th century, such as Alaska, New Zealand, and Patagonia. However, the timing of when glaciers reached their largest sizes in these areas varied greatly, indicating that these changes likely occurred independently in different regions, rather than being part of a global climate event. Therefore, current evidence does not support the idea of global periods of unusually cold or warm temperatures during this time. The terms "Little Ice Age" and "Medieval Warm Period" are not very useful for describing changes in average temperatures across hemispheres or the entire globe. When looking at the Northern Hemisphere as a whole, the "Little Ice Age" only shows a small cooling of less than 1°C compared to late 20th-century temperatures.
The IPCC Fourth Assessment Report (AR4) of 2007 discusses more recent research and focuses on the Medieval Warm Period:
When combined, current temperature reconstructions show more variability in temperature trends over the last 1,000 years than previously noted in the TAR. These reconstructions suggest cooler conditions in the 17th and early 19th centuries and warmer conditions in the 11th and early 15th centuries. However, the warmest temperatures occurred in the 20th century. Because confidence levels in these reconstructions are wide, most results fall within the uncertainty range previously described in the TAR. The main differences between reconstructions involve the strength of past cold periods, especially during the 12th to 14th, 17th, and 19th centuries.
Dating
Scientists do not agree on when the Little Ice Age started, but some events before the coldest times are often mentioned. According to J. M. Lamb of Cambridge University, the Little Ice Age was already happening in Canada, Switzerland, and the North Atlantic region during the 13th and 14th centuries. In the 13th century, ice in the North Atlantic moved southward, and glaciers in Greenland advanced. Stories from that time suggest glaciers were growing in many places worldwide. Using radiocarbon dating on about 150 samples of dead plant material found under ice caps on Baffin Island and Iceland, Miller et al. (2012) said cold summers and ice growth began suddenly between 1275 and 1300, followed by a stronger increase in ice from 1430 to 1455.
In contrast, a study based on glacier lengths showed little change from 1600 to 1850 but a major retreat after that.
Therefore, different dates over 400 years may mark the start of the Little Ice Age:
The Little Ice Age ended in the second half of the 19th century or the early 20th century.
The 6th report of the IPCC describes the coldest period in the last 1,000 years as:
a long period of cooler temperatures starting around the 15th century, with average global temperatures about –0.03 [–0.30 to 0.06] °C lower than the average between 1850 and 1900.
The dates for when the Little Ice Age began and ended vary greatly, depending on the region and data used. In the Northern Hemisphere, the Little Ice Age started between 1200 and 1400 AD. In the Southern Hemisphere, it began about 200 years later.
By region
In 2021, historian Christian Pfister and scientist Heinz Wanner published a study. Their study used temperature data from historical records to show past temperatures in Central Europe. After the year 1500, their work included information from Czech scientist Petr Dobrovolny. Dobrovolny’s research provided monthly, seasonal, and yearly temperature estimates for Germany, Switzerland, and the Czech lands up to 1759, using data from earlier times and later temperature measurements.
Winter temperatures from 1000 to 1999 were generally cold until the late 1800s. A yearly record of winter temperatures from 1170 onward shows that the Little Ice Age had different patterns.
In the 13th century, most winters were cold during the first third of the century and between 1270 and 1280.
During the 14th century, cold winters were common, except between 1340 and 1377.
The 15th century was mostly cold, except during the 1470s. Winters remained cold until 1520.
In the 16th century, cold and warm seasons were about equal until 1540. After that, cold winters became the norm. Especially cold winters happened between 1565 and 1573 and again from 1587 to 1595. Winter temperatures were about 0.9°C below the 1961–1990 average.
In the 17th century, winter temperatures were 1.2°C below the average.
In the 18th century, winter temperatures were 0.9°C below the average.
In the 19th century, winter temperatures were 1.2°C below the average, based on thermometer readings.
In the 20th century, winter temperatures were 0.2°C below the 1961–1990 average. Temperatures rose after 1950.
Conclusion: Cold winter periods became longer and more intense after the 14th century, with peaks in the 15th, 17th, and 19th centuries. Winter temperatures gradually dropped until the early 20th century compared to the 1961–1990 average. This cooling was part of the end of the Little Ice Age in Central Europe, which was caused by global warming.
In the 14th century, summers were slightly cooler than warm ones. The years 1324 to 1340 and 1380 to 1399 were mostly warm, while 1314 to 1322 and 1355 to 1370 were mostly cold. This cold period caused Alpine glaciers to grow, reaching their peak in the 1380s.
Most summers in the 15th century were cold. After a warm period until 1424, the trend reversed. Seven cold summers occurred in the 1450s, likely because of a tropical volcano eruption (Kuwae). Three hot summers happened between 1471 and 1473.
In the 16th century, estimated summer temperatures were 0.2°C below the 1961–1990 average. From 1534 to 1567, ten hot and dry summers raised temperatures by 0.3°C above average, causing glaciers to melt. Later, temperatures dropped with heavy summer rain, reaching a low point in the 1590s and causing Alpine glaciers to grow again.
In the 17th century, summer temperatures were 0.2°C below the 1961–1990 average. Extreme cold and warmth occurred until around 1630 and from 1670 to 1685. Warm summers happened mid-century. After 1675, temperatures dropped by 0.6°C until the turn of the century. Cod fish, which are sensitive to cold, disappeared near the Faroe Islands. Scientist Hubert Lamb concluded that cold Arctic water moved southward.
Warm summers were common in the 18th century, especially between 1718 and 1731. Temperatures were lower between 1760 and 1779, causing Alpine glaciers to grow.
In the 19th century, summers were mostly cold. Average temperatures in Central Europe were 0.6°C below the 1961–1990 average. The first half of the century was cold, leading to glacier growth.
In the 20th century, summers in Central Europe stayed cold until 1927. Temperatures then rose during the warm years from 1943 to 1952. After that, temperatures fluctuated around the 1901–1960 average. Glacier retreat began with slow human-caused warming in the late 19th century and sped up after 1990.
Drangajökull, Iceland’s northernmost glacier, reached its largest size during the Little Ice Age around 1665 or 1765.
The Baltic Sea froze twice, in 1303 and 1306–1307. Unseasonable cold, storms, and rains followed, and the Caspian Sea’s water level rose. The Little Ice Age made winters colder in parts of Europe and North America. Farms and villages in the Swiss Alps were destroyed by advancing glaciers in the mid-17th century. Canals and rivers in Great Britain and the Netherlands froze enough to support ice skating and winter festivals. To keep trade moving during long winters (sometimes 5 months), merchants used boats with planks and skates (runners), creating iceboats. The first River Thames frost fair was in 1608, and the last was in 1814. Changes to bridges and the Thames Embankment affected the river’s flow and depth, making freezes less likely.
In early 1658, a Swedish army used the extremely cold winter to march through Denmark and attack Copenhagen from the west.
Sea ice around Iceland extended for miles, closing harbors to ships. Iceland’s population dropped by half, possibly due to skeletal fluorosis after the 1783 Laki eruption. Cereal crops failed, and people stopped eating grain-based diets.
After 1250, Greenland’s climate became colder and stormier. Norse Viking settlements there shifted from farming to seal hunting for food. By 1300, seal hunting provided over three-quarters of their food. By 1350, exports to Europe declined, and trade stopped. The last document from the settlements was from 1412. Over the next decades, Europeans left Greenland, mainly because of economic factors like more farms in Scandinavia
Central England temperature series
The Central England temperature (CET) is the longest record of temperature measurements in the world. It begins in 1659 and continues without gaps to the present day. This means it starts during the Little Ice Age (LIA), a time period known for colder weather. The CET data help scientists better understand the LIA. It shows that during the LIA, there were more years with extremely cold winters. These years often matched times when frost fairs were held on the Thames River and when very low temperatures were reported in other parts of Europe. The CET data also match well with other scientific estimates of past temperatures. However, not all winters during the LIA were extremely cold. For example, the coldest winter in the CET record (measured by the average temperature of December, January, and February) was in 1684, a year when one of the most famous frost fairs took place. Just two years later, in 1686, the fifth warmest winter in the CET record occurred. Additionally, summer temperatures during the LIA were not much lower than usual. When they were lower, these temperatures often happened after major volcanic eruptions. Therefore, the CET data strongly suggest that the LIA in Europe was a time with more frequent extremely cold winters and slightly lower average temperatures, but not a time of constant cold.
Possible causes
Scientists have identified seven possible causes of the Little Ice Age: changes in Earth's orbit around the Sun, reduced solar activity, increased volcanic activity, changes in ocean currents, shifts in human population that led to reforestation or deforestation, and natural climate variability.
Over the past 2,000 years, changes in Earth's orbit have caused a long-term cooling trend in the northern hemisphere, which continued during the Middle Ages and the Little Ice Age. The Arctic region cooled by about 0.02°C per century during this time. However, the 20th century saw a reversal of this trend, with global temperatures rising due to greenhouse gas emissions.
Solar activity includes events like sunspots and solar flares, which are linked to the Sun's magnetic field. Scientists study past solar activity by analyzing isotopes such as carbon-14 and beryllium-10 found in tree rings and ice. During the Spörer Minimum (1400–1550) and Maunder Minimum (1645–1715), solar activity was very low, and these periods overlapped with the Little Ice Age. However, solar activity measured through isotopes was high between these two minima, similar to levels recorded in 1940, suggesting a complex relationship between solar activity and the Little Ice Age.
A study found that a drop in solar activity around 1230 AD, measured using a specific method, may have contributed to the start of the Little Ice Age. This drop in solar output occurred before a period of increased volcanic activity.
Research by Dmitri Mauquoy and others showed that carbon-14 levels rose rapidly at the start of the Spörer Minimum. This increase matched a sharp drop in temperatures recorded in European peat bogs. However, the timing of this temperature drop did not fully align with changes in solar activity, suggesting a delayed response or other factors at play.
Judith Lean’s 1999 study found that a 0.13% increase in solar irradiance between 1650 and 1790 could have raised Earth’s temperature by 0.3°C. Her research linked solar activity to temperature changes, but measuring long-term solar trends remains challenging due to uncertainties in space-based measurements. Some studies suggest that solar activity may have contributed to only about 55% of temperature changes during the Little Ice Age, with volcanic activity playing a larger role.
During the Little Ice Age, volcanic activity was high. When volcanoes erupt, they release ash and sulfur dioxide into the atmosphere. These particles block sunlight, causing global cooling that can last up to two years. Sulfur dioxide forms sulfuric acid particles in the stratosphere, which further reflect sunlight, reducing the amount of heat reaching Earth.
A severe volcanic eruption in 1257, possibly Mount Samalas in Indonesia, may have triggered the initial cooling of the Little Ice Age. Additional eruptions in 1268, 1275, and 1284 prolonged this cooling. A later eruption in 1452–1453 caused a second cooling period. Cold summers during the Little Ice Age were likely sustained by feedbacks involving sea ice and ocean currents, even after volcanic particles had disappeared from the atmosphere.
Other eruptions during the Little Ice Age, such as Billy Mitchell (c. 1580), Huaynaputina (1600), Mount Parker (1641), Long Island (Papua New Guinea) (ca. 1660), and Laki (1783), also contributed to cooling. The 1815 eruption of Tambora in Indonesia led to the "Year Without a Summer," with frost and snow reported in June and July in Europe and North America.
In the early 2000s, scientists proposed that a slowdown in ocean currents, possibly caused by fresh water from the Medieval Warm Period, may have contributed to the Little Ice Age. This theory links the Little Ice Age to a type of climate event known as a Bond event.