An elephant walked across the river near Blackfriars Bridge in London in February 1814. During the frost fair, the top layers of the river froze solid for four days. A lot of unlicensed alcohol and pop-up shops were part of the festival.
This was the last frost fair of the Thames. For several centuries, they had taken place at wildly irregular intervals. The birth of the circus was witnessed at one of the most celebrated fairs of the Great Frost of 1683-34. Since 1814, the river in central London has not frozen over.
The frost fairs are an example of the consequences of the little ice age. Crop failures and other threats were faced by other communities. One of the stories of the little ice age is that societies are forced to adapt to changing conditions.
It is a long-standing mystery. Why did the climate stay the same for hundreds of years? We are closing in on an explanation thanks to decades of studies. The emerging story involves volcanoes, the oceans, the sun and possibly genocide.
The little ice age was discovered slowly and piecemeal because there were lots of documentary records from around Europe. Grain prices rose because of crop failures and ships, which were reflected in records.
The cooling was not continuous – it came in waves that reached different places at different times and magnitudes
The term "little ice age" was created by a Dutch-born geologist named Franois Matthes, who in 1939 reported that glaciers in the Sierra Nevada in California had regrown. It took decades to narrow down the time period.
The Climatic Research Unit at the University of East Anglia was founded by British climatologist Hubert Lamb. Lamb used European temperature records going back many centuries to identify a warm climate around AD 1000 and a decline in temperature levels around 1200. The cold period was upsetting for the human economies of those times.
Climatologists have tried to specify the duration and extent of the ice age, but it has been difficult. Most of the records showing the cooling are from Europe.
Alexander Koch is a professor at Simon Fraser University in British Columbia, Canada. In China, the period was marked by a wet but not cooler climate.
The cooling was not continuous, according to Dagomar Degroot of Georgetown University.
The classical definition of the start and end of the ice age is between 1400 and 1850. Some people say the start date is 1300 to 1850. She says there is broad agreement that the period 1400-1800 is within the little ice age. The frost fair was at the end of the period.
The little ice age was not an ice age. We have been in one of these periods for more than 2.5m years. The ice sheets have waned over time. The most recent ice advance occurred from about 115,000 to 11,700 years ago. We have been in a warm period called the Holocene since then.
The little ice age is small. The last part of the last ice age is thought to have been cooler than the previous 4,000 years. Even though this small change mattered, some people were aware of the anomalies.
What was happening? The story isn't completely settled, but researchers are more confident about the initial event.
There are eruptions that are happening in clusters. 25 major eruptions from the past 2,500 years were identified by using ice core data. There were huge eruptions of the Samalas volcano in Indonesia and the other volcanos in Mexico between 1200 and 1400.
The layer of the atmosphere above the weather is called the stratosphere. The aerosols reflect some of the sun's rays back into space. The 1991 eruption of Mount Pinatubo in the Phillippines has caused surface cooling.
Positive feedbacks in the climate system can be set off by big eruptions in clusters. Several years of cooler temperatures cause sea ice to expand. Sea ice reflects more radiation back into space than dark blue water.
Moffa-Sánchez says there can be knock-on effects in the ocean. If the winds change, huge rafts of sea ice can be carried into the Labrador Sea. They interfere with the huge Atlantic currents that carry warm water from the tropics towards Europe.
This is a complex story, in which the slight initial cooling from the volcanoes causes changes in the Earth system that lead to more and lasting cooling. It seems to hold true. The modelling study found that it was not possible to explain the ice age without using volcanic eruptions.
The sun could be a factor. Over the 11-year solar cycle, the amount of energy it pumps out varies from a maximum to a minimum and back again. The effects on Earth are small and hard to detect, but the sun can have an impact.
Our star has entered several grand minimums in the past 1000 years, in which it spends several decades being less active. Between 1790 and 1820 was the most recent time period. The Maunder Minimum was preceded by this. The Wolf Minimum is thought to have been between 1460 and 1550. The grand minima can cool the planet by a small amount.
Moffa-Sánchez says that grand minima may have played a role in some episodes. She found evidence that grand minima affect wind patterns and ocean currents.
It seems unlikely that grand minima alone caused the ice age. Climate impacts of grand minima are much smaller than those of massive eruptions.
The suggestion is that this cold spell was caused by humanity – in a truly horrible way
It is possible that a solar maximum in the late 1300s played a role. The study found that the wind patterns interfered with the Atlantic warm water current.
This isn't an either- or debate, says Moffa-S.nchez.
Climate shifts came in waves, not because of a sudden change to a cooler state, but because of many causes.
One big puzzle is still unresolved. The lowest period of the ice age was in 1610 and it doesn't coincide with a grand minimum. The explosion of the Huaynaputina in 1600 was large, but it wasn't exceptional.
The suggestion is that the cold spell was caused by humanity.
Christopher Columbus arrived in the Americas in 1492. Europeans colonised them over the following decades. They fought with Indigenous Americans and killed them. They brought diseases that were even more lethal. It was one of the worst diseases, killing millions.
This may have had an impact on the climate, as well as being a genocide and a tragedy. Many Indigenous Americans were farmers who cleared forests for their crops and when they died the trees grew back, drawing carbon dioxide out of the air and cooling the planet. This scenario was first outlined by William Ruddiman in 2003 as part of his hypothesis that humans have been affecting Earth's climate for thousands of years.
Modelling studies show tentative support for the idea that mass deaths among Indigenous Americans lead to climate cooling. It has been controversial because there are so many uncertainties about the key numbers.
Koch and his colleagues published an updated analysis in 2019. They tried to quantify everything from the number of people who died to the extent of regrowth. The European arrival led to 56 million deaths by 1600. This terrible toll resulted in trees growing again on 56m hectares of land, removing 27.4 billion kilowatts of carbon dioxide from the air.
It's a really interesting theory, says Degroot. We don't know how land use is changing in other parts of the world.
While the question of whether human society contributed to the little ice agee remains up for discussion, what is clear is that the little ice age affected human society.
The settlers of the Norse religion made their home in the island in 980 and stayed there for hundreds of years before abandoning it in the 1400s. The little ice age may have played a role in that. A study published in March found no sign of cooling, but it did find a drying trend, which would have meant less grass to feed livestock.
It's important to remember that people were not passive victims, says Degroot.
Despite the increase in sea ice, there was often remarkable activity. There was a shortage of vegetable oil and whale oil that caused European whalers to leave the shores of Svalbard in 1611.
Despite the cold winters, the period between 1560 and 1720 was a golden age for the Dutch Republic. Local crop failures were less of a problem because it did not depend on home-grown agriculture. Merchant ships and their operators devised ingenious ways to cope with the cold, and the Dutch thrived while their neighbours struggled.
It so rarely is what you would expect. As the climate crisis becomes more intense, we can learn from past societies how they responded to the little ice age.
The ice age was just a small sample. The average global temperature cooled by a fraction of a degree, but we have already warmed it by 1.1C, and are set to blow past 1.5C in the next few decades.
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