The Little Ice Age (LIA) was a time when temperatures in certain areas, especially near the North Atlantic, were cooler than usual. It was not a global ice age that covered the entire planet. The term "Little Ice Age" was first used in scientific writing by François E. Matthes in 1939. Scientists often describe this period as lasting from the 16th to the 19th centuries, though some researchers suggest it may have begun around 1300 and ended around 1850.

According to NASA Earth Observatory, there were three major cold periods during the LIA. These occurred around 1650, 1770, and 1850, with short periods of slightly warmer temperatures in between. The Intergovernmental Panel on Climate Change’s Third Assessment Report noted that the LIA’s timing and effects were mostly linked to regional climate changes in different parts of the world, not a single global event. At most, the Northern Hemisphere experienced only mild cooling during this time.

Scientists have suggested several possible causes for the LIA. These include lower levels of solar energy reaching Earth, 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, epidemics in the Americas after European contact, and conflicts like those led by Genghis Khan.

Areas involved

The Intergovernmental Panel on Climate Change Third Assessment Report (TAR) of 2001 explained the regions that were impacted. The IPCC Fourth Assessment Report (AR4) of 2007 covers newer studies and pays special attention to the Medieval Warm Period.

Dating

There is no agreement on when the Little Ice Age began, but several events before the coldest times are often mentioned. In the 13th century, ice in the North Atlantic started moving southward, and glaciers in Greenland also grew. Stories from people suggest glaciers expanded in many places around the world. Based on studying about 150 samples of dead plants found under ice on Baffin Island and Iceland, Miller et al. (2012) say cold summers and ice growth began suddenly between 1275 and 1300. This was followed by a much stronger increase in ice between 1430 and 1455.

However, a study looking at how long glaciers were shows little change from 1600 to 1850, but glaciers started shrinking strongly after that.

Because of this, several dates over 400 years might mark the start of the Little Ice Age:

• 1250, when Atlantic ice began growing, possibly because of the large eruption of the Samalas volcano in 1257 and the cold period it caused.
• 1275 to 1300, when plant samples showed plants were killed by glaciers.
• 1300, when warm summers in Northern Europe became unreliable.
• 1315, when heavy rains and the Great Famine of 1315–1317 happened.
• 1560 to 1630, when global glaciers, called the Grindelwald Fluctuation, started expanding.
• 1650, which marks the coldest years in the middle of the Little Ice Age, not its start.

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:

The start and end of the Little Ice Age 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 studied past temperatures in Central Europe using data from written records. They used temperature measurements based on historical documents. After the year 1500, their research included an article by Czech geographer Petr Dobrovolny, which provided monthly, seasonal, and yearly temperature estimates for Germany, Switzerland, and the Czech lands up to 1759, using temperature data and later measurements.

Winter temperatures from 1000 to 1999 were generally cold until the late 1800s. A yearly reconstruction of winter temperatures from 1170 onward shows a different pattern of the Little Ice Age.

Winters in the 13th century were mostly cold, especially in the first third of the century and between 1270 and 1280.

In the 14th century, cold winters were common, except for 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 common, with especially harsh winters between 1565 and 1573 and again from 1587 to 1595. Winter temperatures were about 0.9 degrees Celsius (±0.69 degrees Celsius) below the 1961–1990 average.

In the 17th century, temperatures were 1.2 degrees Celsius (±0.69 degrees Celsius) below the average.

In the 18th century, temperatures were 0.9 degrees Celsius (±0.69 degrees Celsius) below the average.

In the 19th century, temperatures were 1.2 degrees Celsius below the average, based on thermometer readings.

In the 20th century, temperatures were 0.2 degrees Celsius below the 1961–1990 average, with warmer years becoming more common after 1950.

Conclusion: Cold winter periods became longer and stronger since the 14th century, with the most severe periods in the 15th, 17th, and 19th centuries. Winter temperatures gradually decreased until the early 20th century compared to the 1961–1990 average, showing 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 1324–1340 and 1380–1399 were mostly warm, while the years 1314–1322 and 1355–1370 were mostly cold. This cold period caused Alpine glaciers to grow, reaching their peak in the 1380s.

In the 15th century, cold summers were common. 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 0.2 degrees Celsius (±0.49 degrees Celsius) below the 1961–1990 average. Ten hot and dry summers between 1534 and 1567 raised temperatures by 0.3 degrees Celsius (±0.49 degrees Celsius), 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 degrees Celsius (±0.49 degrees Celsius) below the 1961–1990 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 degrees Celsius until the start of the 18th century. Cod fish disappeared from the Faroe Islands due to cold water. Climatologist Hubert Lamb concluded 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.

In the 19th century, summers were mostly cold. Average temperatures in Central Europe were 0.6 degrees Celsius 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 were cold until 1927. Temperatures rose until the warm years from 1943 to 1952, after which they fluctuated around the 1901–1960 average. Glacier retreat began in the late 19th century due to human-caused warming and accelerated 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 unusual cold, storms, and rising Caspian Sea levels. The Little Ice Age brought colder winters to parts of Europe and North America. In the mid-17th century, glaciers destroyed farms and villages in the Swiss Alps. In Great Britain and the Netherlands, canals and rivers froze enough for ice skating and winter festivals. Merchants used iceboats with runners to move goods during long winters. The first River Thames frost fair was in 1608, and the last was in 1814. Changes to the river, like new bridges and the Thames Embankment, reduced freezing.

In early 1658, a Swedish army used the extreme cold to attack Copenhagen.

Sea ice around Iceland closed harbors to ships. Iceland’s population dropped by half, possibly due to health issues after the 1783 Laki eruption. Cereal crops failed, and people reduced their reliance on grain.

After around 1250, Greenland’s climate became colder and stormier. Norse Viking settlements shifted to seal hunting for food, relying on it for over three-quarters of their

Central England temperature series

The Central England temperature (CET) is the longest recorded set of temperature measurements in the world, beginning in 1659 and continuing to the present day. This means it starts during the middle of the Little Ice Age (LIA), no matter how the LIA is defined. The CET data provides important information about 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 matches well with older climate studies about average temperature trends. However, not all winters during the LIA were extremely cold in the CET record. For example, the coldest winter (measured by the average temperature of December, January, and February) in the entire CET record was in 1684, the year of one of the most famous frost fairs. 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 suggests that the LIA in Europe should be seen as a time when extremely cold winters happened more often, leading to slightly lower average temperatures, but not as a time of constant cold.

Possible causes

Scientists think they might 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, changes in human population that caused more or fewer trees, and natural changes in Earth's climate.

Changes in Earth's orbit have caused a slow cooling in the northern hemisphere for about 2,000 years, including during the Middle Ages and the Little Ice Age. The Arctic cooled by about 0.02 degrees Celsius every 100 years. However, in the 20th century, global temperatures began to rise again, likely because of gases from human activities.

Solar activity includes events like sunspots and solar flares on the Sun's surface. Scientists can study past solar activity by looking at isotopes like carbon-14 and beryllium-10 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 was not always low during the Little Ice Age, so the connection between the Sun and the Little Ice Age is not simple.

One study suggests that a drop in solar activity around 1230 AD might have started the Little Ice Age, as this drop happened before major volcanic eruptions.

A study by Dmitri Mauquoy and others found that carbon-14 levels rose quickly at the start of the Spörer Minimum. This rise matched a drop in temperatures recorded from European peat bogs. However, the timing of this temperature drop did not always match changes in solar activity, making the relationship unclear.

In 1999, Judith Lean found that a 0.13% increase in solar energy between 1650 and 1790 could have raised Earth's temperature by 0.3 degrees Celsius. Her research showed a possible link between solar activity and global temperatures, but measuring long-term solar energy changes is difficult because of uncertain measurements. Some studies suggest that solar energy might have been higher during the Maunder Minimum than today, but this is still uncertain.

During the Spörer Minimum and Maunder Minimum, sunspots were rare, and levels of isotopes like 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 volcanic activity, not solar activity, likely caused most of the 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 sulfur into the atmosphere. These eruptions may have caused long-term cooling. Other eruptions, like those from Billy Mitchell (1580), Huaynaputina (1600), and Laki (1783), also contributed to cooling. The 1815 eruption of Tambora caused the "Year Without a Summer" in 1816.

In the early 2000s, scientists proposed that changes in ocean currents, such as the weakening of the North Atlantic Gyre, might have caused the Little Ice Age. This could have happened if large amounts of fresh water entered the North Atlantic during the Medieval Warm Period before the Little Ice Age. Some scientists call the Little Ice Age a "Bond event" because of this connection.