The Little Ice Age (LIA) was a time when temperatures dropped in certain areas, especially in the North Atlantic region. It was not a global ice age that covered the entire Earth. The term "Little Ice Age" was first used in scientific writing by François E. Matthes in 1939. Scientists usually describe this period as lasting from the 16th to the 19th centuries, but some researchers suggest a longer time span from about 1300 to about 1850.
According to NASA Earth Observatory, there were three major cold periods during the LIA. These began around 1650, 1770, and 1850, and each was followed by short periods of mild warming. The Intergovernmental Panel on Climate Change’s Third Assessment Report noted that the timing and locations of cooling during the LIA suggest climate changes occurred in different regions independently, rather than a global increase in glaciers at the same time. At most, the Northern Hemisphere experienced only slight cooling during this period.
Scientists have proposed several possible causes for the LIA. These include periods when the sun’s energy was lower, increased volcanic activity, changes in ocean currents, variations in Earth’s orbit and tilt, natural climate changes, and decreases in human populations due to events like the Black Death and diseases that spread in the Americas after European contact.
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 shows that glaciers grew larger in some regions outside Europe before the 20th century, such as Alaska, New Zealand, and Patagonia. However, the timing of these glacial advances varied in different areas, suggesting that these changes were likely caused by separate regional climate patterns, not a single global event. Therefore, current evidence does not support widespread periods of unusually cold or warm temperatures worldwide during this time. The terms "Little Ice Age" and "Medieval Warm Period" are not very useful for describing temperature trends across the entire globe or both hemispheres. When looking at the Northern Hemisphere alone, the "Little Ice Age" was a small cooling period, with temperatures less than 1°C lower than late 20th-century levels.
The IPCC Fourth Assessment Report (AR4) of 2007 reviewed more recent research and focused on the Medieval Warm Period:
When combined, current studies show that temperature trends over the past 1,000 years had more variation than previously thought. These studies 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 in these studies is limited, all reconstructions fall within the range of uncertainty mentioned in the TAR. The main differences between these studies are the size of past cooling events, especially during the 12th to 14th centuries, 17th, and 19th centuries.
Dating
Experts do not agree on when the Little Ice Age began. However, certain events before the coldest times in history are often mentioned. According to J. M. Lamb of Cambridge University, the Little Ice Age started in parts of Canada, Switzerland, and the North Atlantic region during the 13th and 14th centuries. In the 13th century, ice in the North Atlantic moved farther south, and glaciers in Greenland expanded. Stories from that time suggest glaciers grew in many places worldwide. Scientists studied about 150 samples of dead plant material found under ice on Baffin Island and Iceland. Using a method called radiocarbon dating, they found that colder summers and ice growth began suddenly between 1275 and 1300. This was followed by a stronger increase in ice between 1430 and 1455.
A different study that looked at glacier lengths showed little change between 1600 and 1850 but a major retreat after that time.
Because of these differences, the start of the Little Ice Age could be marked by several dates over a 400-year period.
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 time in the last 1,000 years as:
a period lasting several hundred years with lower-than-average temperatures that began around the 15th century. Global mean surface temperature (GMST) was about –0.03 [–0.30 to 0.06] °C from 1450 to 1850 compared to the average from 1850–1900.
Definitions for when the Little Ice Age started and ended vary widely, depending on the region and data used. In the Northern Hemisphere, the Little Ice Age began between 1200 and 1400 AD. In the Southern Hemisphere, it started about 200 years later.
By region
In 2021, historian Christian Pfister and climatologist Heinz Wanner created a study of seasonal temperatures in Central Europe using temperature data from historical records. This study used information from documents and writings. After the year 1500, the study included work by Czech geographer Petr Dobrovolny, who provided monthly, seasonal, and yearly temperature estimates for Germany, Switzerland, and the Czech lands up to 1759, based on temperature data and later measurements.
Winters from 1000 to 1999 were generally cold until the end of the 19th century. A study of yearly winter temperatures from 1170 onward shows a different pattern related to the Little Ice Age.
Most winters in the 13th century were cold, especially during the first third of the century and between 1270 and 1280.
In the 14th century, cold winters were common, except for the 37 years between 1340 and 1377.
The 15th century was mostly cold, except for the 1470s. Winters remained mostly cold until 1520.
In the 16th century, cold and warm seasons were about equal until 1540. After that, cold winters became more common, with especially harsh winters between 1565 and 1573 and again from 1587 to 1595. On average, winter temperatures were about 0.9°C (±0.69°C) below the 1961–1990 average.
In the 17th century, temperatures were about 1.2°C (±0.69°C) below the average.
In the 18th century, temperatures were about 0.9°C (±0.69°C) below the average.
In the 19th century, temperatures were about 1.2°C below the average, based on thermometer readings.
In the 20th century, temperatures were about 0.2°C below the 1961–1990 average, with warmer temperatures becoming more common after 1950.
Conclusion: Cold winter periods have become longer and more intense since the 14th century, with peaks in the 15th, 17th, and 19th centuries. The gradual cooling of winters until the early 20th century compared to the 1961–1990 average was one sign that the Little Ice Age in Central Europe was ending due to 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 the years 1314 to 1322 and 1355 to 1370 were mostly cold. This cold period caused Alpine glaciers to grow, reaching their peak in the 1380s.
In the 15th century, summers were mostly cold. After a warm period until 1424, the trend changed. Seven cold summers occurred in the 1450s, possibly linked to a tropical volcano eruption (Kuwae). Three hot summers occurred between 1471 and 1473.
In the 16th century, temperatures were about 0.2°C (±0.49°C) below the 1961–1990 average. Ten hot and dry summers between 1534 and 1567 raised temperatures by 0.3°C (±0.49°C) above average, causing glaciers to melt slightly. Later, temperatures dropped with heavy summer rain, reaching a low point in the 1590s and causing Alpine glaciers to advance again.
In the 17th century, temperatures were about 0.2°C (±0.49°C) below the average. Cold and warm extremes were common until around 1630 and from 1670 to 1685, with warm summers in the middle of the century. After 1675, temperatures dropped by about 0.6°C until the start of the 18th century. Cod fish, which cannot survive cold waters, disappeared from the Faroe Islands. Climatologist Hubert Lamb noted that cold Arctic water spread southward.
In the 18th century, summers were mostly warm, especially between 1718 and 1731. Temperatures were lower between 1760 and 1779, causing Alpine glaciers to advance again.
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 advances.
In the 20th century, summers in Central Europe remained cold until 1927. Temperatures then rose during the warm decade from 1943 to 1952, after which they stayed near 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, followed by years of "unseasonable cold, storms, and rains" and a rise in the Caspian Sea’s level. The Little Ice Age brought colder winters to parts of Europe and North America. In the Swiss Alps, farms and villages were destroyed by advancing glaciers in the mid-17
Central England temperature series
The Central England temperature (CET) is the longest continuous record of temperature measurements in the world, starting in 1659 and continuing to the present day. This record begins during the Little Ice Age (LIA), a period of cooler global temperatures. The CET data help scientists better understand the LIA. It shows that during this time, there were more winters with unusually low temperatures. These cold winters often matched years 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 older climate studies in showing similar average temperature trends. However, not all winters during the LIA were extremely cold. For example, the coldest winter in the CET record occurred in 1684, a year famous for a major frost fair. Just two years later, in 1686, the fifth warmest winter in the CET record happened. Additionally, summer temperatures during the LIA were not much lower than usual, except when volcanic eruptions occurred, which caused temporary cooling. The CET data suggest that the LIA in Europe was a time of more frequent extremely cold winters and slightly lower average temperatures, but not a time of constant cold.
Possible causes
Scientists have found seven possible reasons for the Little Ice Age: changes in Earth's orbit around the Sun, less activity from the Sun, more volcanic eruptions, changes in ocean currents, shifts in human population that caused forests to grow or shrink, and natural changes in Earth's climate.
Changes in Earth's orbit have caused a long-term cooling trend in the northern hemisphere for the past 2,000 years. This cooling continued during the Middle Ages and the Little Ice Age. The Arctic cooled by about 0.02°C every 100 years during this time. However, global temperatures began to rise in the 20th century due to greenhouse gases.
Solar activity refers to changes on the Sun, such as sunspots and solar flares. These changes affect the Sun's magnetic field, which extends into space as the solar wind. Scientists study past solar activity by looking at isotopes like carbon-14 and beryllium-10, which are created when cosmic rays hit Earth's atmosphere and are stored in tree rings and ice. Two periods of very low solar activity, the Spörer Minimum (1400–1550) and the Maunder Minimum (1645–1715), overlapped with the Little Ice Age. However, solar activity was sometimes high during these times, showing that the relationship between solar activity and the Little Ice Age is not simple.
A study suggested that a drop in solar activity around 1230 AD might have started the Little Ice Age. This drop happened before major volcanic eruptions began.
A study by Dmitri Mauquoy et al. found that carbon-14 levels rose quickly at the start of the Spörer Minimum. This rise matched a sharp drop in temperatures recorded in European peat bogs. However, the timing of the temperature drop was about 50 years after the start of the Spörer Minimum. This delay does not fully explain later changes in solar activity and temperatures.
Judith Lean’s 1999 study showed that solar activity might have influenced the Little Ice Age. She found that solar radiation increased by 0.13% between 1650 and 1790, which could have raised Earth’s temperature by 0.3°C. Her research suggested a possible link between solar activity and temperature changes, but measuring long-term solar radiation trends from space remains challenging due to uncertainties in measurements.
During the Spörer and Maunder Minima, sunspots were rare, and levels of carbon-14 and beryllium-10 increased. However, colder temperatures in the Little Ice Age began before the Maunder Minimum and lasted after it ended. Studies show that solar activity alone did not cause the cooling, as volcanic activity and other factors played larger roles.
A 2012 study by Miller et al. linked the Little Ice Age to four major volcanic eruptions between 1257 and 1284. These eruptions released large amounts of sulfur into the atmosphere, which blocked sunlight and cooled the planet. Other eruptions, such as those at Billy Mitchell (1580), Huaynaputina (1600), and Laki (1783), also contributed to cooling. The 1815 eruption of Mount Tambora caused the "Year Without a Summer," with extreme cold in 1816.
Some scientists proposed that changes in ocean currents, like the slowing of the thermohaline circulation, might have caused the Little Ice Age. This could have happened if fresh water from the Medieval Warm Period disrupted ocean currents. Researchers sometimes call the Little Ice Age a "Bond event" because of its connection to past climate shifts.