The Little Ice Age (LIA) was a time when temperatures dropped in certain areas, especially in the North Atlantic region. It was not a full ice age that covered the entire world. The term "Little Ice Age" was first used in scientific writing by François E. Matthes in 1939. The period is usually described as lasting from the 16th to the 19th centuries, though some scientists suggest it may have started around 1300 and ended around 1850.
NASA Earth Observatory identifies three major cold periods during the LIA. These began around 1650, 1770, and 1850, with brief warm periods between them. The Intergovernmental Panel on Climate Change’s Third Assessment Report stated that the timing and locations of cooling during the LIA suggest that climate changes were mostly regional, not global. At most, the Northern Hemisphere experienced only slight cooling during this time.
Possible causes of the LIA include lower levels of solar energy, increased volcanic activity, changes in ocean currents, shifts in Earth’s orbit and tilt, natural climate variations, and decreases in human populations due to events such as the Black Death, wars, and disease outbreaks in the Americas after European contact.
Areas involved
The Intergovernmental Panel on Climate Change Third Assessment Report (TAR) from 2001 described areas affected by climate changes:
Evidence from mountain glaciers shows that glacier growth occurred in some regions outside Europe before the 20th century, such as Alaska, New Zealand, and Patagonia. However, the timing of the largest glacier advances in these areas varied, suggesting these changes were likely due to separate regional climate patterns rather than a global event. Therefore, current evidence does not support worldwide periods of unusual cold or warmth during this time. The terms "Little Ice Age" and "Medieval Warm Period" are not helpful for describing overall temperature trends in the Northern or Southern Hemispheres. When looking at the Northern Hemisphere alone, 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) from 2007 discusses more recent research, especially about the Medieval Warm Period:
When combined, current studies show more temperature changes over the past 1,000 years 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 results fall within the uncertainty range mentioned in the TAR. Differences between studies mainly involve the strength of past cooling periods, especially during the 12th to 14th centuries, 17th century, and 19th century.
Dating
There is no agreement on exactly when the Little Ice Age began, but some events before the coldest periods are often mentioned. J. M. Lamb from Cambridge University said 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, pack ice started moving south in the North Atlantic, and glaciers in Greenland also expanded. Stories from people suggest glaciers grew in many places around the world. Based on radiocarbon dating of about 150 plant samples found under ice on Baffin Island and Iceland, Miller et al. (2012) said cold summers and ice growth began suddenly between 1275 and 1300, followed by a major increase from 1430 to 1455.
However, a study of glacier lengths shows little change between 1600 and 1850, but glaciers began to shrink strongly after that time.
Because of these different findings, the start of the Little Ice Age could be marked by any of several dates over a 400-year range.
The Little Ice Age ended in the second half of the 19th century or the early 20th century.
The 6th report from the IPCC describes the coldest time in the last 1,000 years as:
a period lasting several centuries with cooler temperatures starting around the 15th century. The average global temperature was –0.03 [–0.30 to 0.06] °C lower than the average between 1850 and 1900 during the years 1450 to 1850.
The start and end dates of the Little Ice Age vary widely, depending on the region and the data used. In the Northern Hemisphere, the Little Ice Age began between 1200 and 1400 AD. In the Southern Hemisphere, the start was delayed by about 200 years.
By region
In 2021, historian Christian Pfister and climatologist Heinz Wanner created a study of seasonal temperatures in Central Europe using temperature measures based on historical records. After the year 1500, their study used an article by Czech geographer Petr Dobrovolny, which includes monthly, seasonal, and yearly temperature estimates for Germany, Switzerland, and the Czech lands based on temperature measures up to 1759 and later temperature measurements.
Winters from 1000 to 1999 were generally cold until the end of the 19th century. A yearly study of winter temperatures from 1170 onward shows a different pattern of the Little Ice Age.
Winters in the 13th century were mostly cold only in the first part 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 balanced until 1540. After that, cold winters became the norm, with especially severe winters between 1565 and 1573 and again from 1587 to 1595. Overall, winter temperatures were about 0.9°C (±0.69°C) below the 1961–1990 average.
In the 17th century, temperatures were 1.2°C (±0.69°C) below average.
In the 18th century, temperatures were 0.9°C (±0.69°C) below average.
In the 19th century, temperatures were 1.2°C below average based on thermometer readings.
In the 20th century, temperatures were 0.2°C below the 1961–1990 average, with warmer temperatures becoming more common after 1950.
Conclusion: The length and strength of cold winter periods have increased since the 14th century, reaching their peak in the 15th, 17th, and 19th centuries. The slow decrease in winter temperatures until the early 20th century, compared to the 1961–1990 measurement period, showed the end of the Little Ice Age in Central Europe due to global warming.
In the 14th century, summers were slightly cooler than warm ones. The years from 1324 to 1340 and from 1380 to 1399 were mostly warm, while the years from 1314 to 1322 and from 1355 to 1370 were mostly cold. This cold period caused Alpine glaciers to grow, reaching their peak in the 1380s.
Cold summers were common in the 15th century. After a relatively warm period until 1424, the trend changed. Seven cold summers occurred in the 1450s, likely linked to a tropical volcano eruption (Kuwae). Notably, three hot summers happened between 1471 and 1473.
In the 16th century, temperatures were 0.2°C (±0.49°C) below the 1961–1990 average. Ten hot and dry summers from 1534 to 1567 raised temperatures by 0.3°C (±0.49°C) above average, causing glaciers to melt slightly. Later, temperatures dropped due to heavy summer rain, reaching a low in the 1590s and causing Alpine glaciers to advance again.
In the 17th century, temperatures were 0.2°C (±0.49°C) below average. Extreme cold and warmth occurred until around 1630 and from 1670 to 1685, with warm summers in the middle of the century. After 1675, temperatures dropped by an average of 0.6°C until the start of the 18th century. Cod fish, which are sensitive to cold, disappeared from the waters around the Faroe Islands. English climatologist and historian Hubert Lamb concluded that cold Arctic water spread 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 advance again.
Cold summers were common in the 19th century. Average temperatures in Central Europe were 0.6°C below the 1961–1990 average. The first half of the century was mostly 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 fluctuated around the 1901–1960 average. Glacier retreat began slowly in the late 19th century and sped up after 1990 due to human-caused warming.
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 level." The Little Ice Age brought colder winters to parts of Europe and North America. Farms and villages in the Swiss Alps were destroyed by advancing glaciers during the mid-17th century. Canals and rivers in Great Britain and the Netherlands often froze enough to support ice skating and winter festivals. To continue trade during long winters lasting up to five months, merchants used boats with planks and skates (runners), leading to the creation of iceboats. The first River Thames frost fair was in 1608, and the last was in 1814. Changes to bridges
Central England temperature series
The Central England temperature (CET) is the longest record of temperature measurements in the world, beginning in 1659 and continuing to the present day. This record started during the Little Ice Age (LIA), a period of colder global temperatures. The CET data help scientists better understand the LIA. It shows that during the LIA, there were more winters with extremely cold temperatures. These cold winters often happened at the same time as frost fairs on the Thames River and reports of very low temperatures in other parts of Europe. The CET data also match other scientific estimates of average temperatures from the past. However, not all winters during the LIA were extremely cold. For example, the coldest winter in the CET record was in 1684, a year known for a famous frost fair. 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, this often happened after major volcanic eruptions. 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 unending cold.
Possible causes
Scientists have identified 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, changes in human population that caused forests to grow or shrink, and natural changes in Earth's climate.
Over the past 2,000 years, changes in Earth's orbit have caused a long-term cooling trend in the Northern Hemisphere, which lasted through the Middle Ages and the Little Ice Age. The Arctic cooled by about 0.02°C every 100 years during this time. However, starting in the 20th century, global temperatures began to rise again, likely because of greenhouse gases.
Solar activity includes changes on the Sun, such as sunspots and solar flares. These changes are linked to the Sun's magnetic field. 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 during these times was not always low, and the connection between solar changes and the Little Ice Age is not clear.
A study suggested that a drop in solar activity around 1230 AD might have started the Little Ice Age. This drop in solar output happened before major volcanic eruptions began.
Research by Dmitri Mauquoy and others found that carbon-14 levels rose quickly at the start of the Spörer Minimum, which matched a sharp drop in temperatures recorded in European peat bogs. However, the timing of this temperature drop did not always match changes in solar activity.
Judith Lean's 1999 study found that a 0.13% increase in solar energy between 1650 and 1790 could have raised Earth's temperature by 0.3°C. Her work showed a possible link between solar activity and temperature changes, but measuring long-term solar energy trends is difficult because of uncertainties in space-based measurements.
During the Little Ice Age, especially during the Spörer and Maunder Minima, sunspots were rare, and isotopes like carbon-14 and beryllium-10 increased. However, colder temperatures in the Northern Hemisphere began before the Maunder Minimum and lasted after it ended. Studies suggest that volcanic activity, not solar changes, had a bigger effect on cooling during the Little Ice Age.
A 2012 study by Miller et al. linked the Little Ice Age to four large volcanic eruptions between 1257 and 1284, which released large amounts of sulfur into the atmosphere. These eruptions may have caused the cooling. Volcanic eruptions release ash and sulfur dioxide, which form particles in the stratosphere that reflect sunlight, reducing the amount of heat reaching Earth.
Other eruptions during the Little Ice Age, such as those at Billy Mitchell (1580), Huaynaputina (1600), Mount Parker (1641), Long Island (1660), and Laki (1783), likely contributed to cooling. The 1815 eruption of Tambora in Indonesia caused the "Year Without a Summer," with severe cold in 1816.
In the early 2000s, scientists proposed that a slowdown in ocean current movement, specifically in the North Atlantic, might have caused the Little Ice Age. This could have been triggered by fresh water from the Medieval Warm Period before the Little Ice Age. Some researchers call the Little Ice Age a "Bond event," a term for major climate shifts.