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When Was the Little Ice Age?

Controversial Dates for the 17th Century Cold Climate

Aug 6, 2008

Global Temperature Reconstructions, Robert A Rohde/Global Warming Art

Most climate scientists agree that the late 17th century was the Little Ice Age, but there is some disagreement on the exact beginning and end.

The Little Ice Age should not be confused with the ice ages. The most recent ice age occurred many thousands of years ago. Geologic evidence indicates that temperatures were so cold that glaciers extended to mid latitude regions. The Little Ice Age was a few hundred years ago. It was colder than normal, but normally temperate regions did not experience glaciers

Dates of the Little Ice Age

The 17th century was a period of much colder than normal temperatures, and for that reason it is called the Little Ice Age. The written records for this period are less accurate than modern records, making it difficult to determine the exact length and severity of the Little Ice Age. The shortest time span estimated for the Little Ice Age is the 17th century. Early estimates date the beginning of the Little Ice Age as 1350 to 1400. Estimates of the end of the Little Ice Age range to as late as 1850.

Climate Reconstruction

The lack of accurate weather records forces climate scientists to use various proxies to reconstruct the climate during the Little Ice Age. Studies of tree rings are the most common, but not only, proxy. Using such proxies climate researchers have reconstructed past average global temperatures to a reasonable degree of accuracy. In the figure, the most recent temperature reconstruction is in red.

The coldest period of the last 1,000 years was the 17th century, so few dispute that this time period was part of the Little Ice Age. It was cooler than the 1,000 year average, but not as cold as the 17th century, from about the beginning of the 14th century to the later part of the 19th century. There were also a few periods during this time when it was fairly warm. Hence there is some dispute about the extent of the Little Ice Age.

From about 1000 to the early 13th century it was nearly as warm as now. A cooling trend started in the latter part of the 13th century. Some climate researchers claim that the Little Ice Age started as early as 1350. It was nearly as cold as the 17th century around 1350 and 1450, but there were less cool periods around 1400 and the early 1500s. Because it was not continuously cold from 1350 to the 17th century, researchers can argue that the Little Ice Age did not start until the 17th century.

Climate researchers trying to set the dates for the end of the Little Ice Age encounter the same problem. The late 1700s were nearly as warm as the average for the past 1000 years, so the Little Ice Age could have ended then. However the first part of the 19th century was again quite cold, so it is equally possible to claim that the Little Ice Age lasted until 1850. (Foukal et al. 2006)

The exact dates of the Little Ice Age are hard to pin down because the relatively long period that was cooler than normal contained shorter warm intervals. The cooler and warmer periods correspond fairly well to periods of decreased and increased sunspot activity, such as the Maunder minimum. Because the Sun's total energy output is related to the amount of sunspot activity the climate changes over the past 1,000 years were likely caused by changes in the solar activity cycle and the resulting solar variability.

When Was the Little Ice Age?

Controversial Dates for the 17th Century Cold Climate

Dates of the Little Ice Age

Climate Reconstruction

Further Reading