Throughout the Little Ice Age, the world experienced heightened volcanic activity.[72] When a volcano erupts, its ash reaches high into the atmosphere and can spread to cover the whole earth. This ash cloud blocks out some of the incoming solar radiation, leading to worldwide cooling that can last up to two years after an eruption. Also emitted by eruptions is sulfur in the form of sulfur dioxide gas. When this gas reaches the stratosphere, it turns into sulfuric acid particles, which reflect the sun's rays, further reducing the amount of radiation reaching Earth's surface.
A recent study found that an especially massive tropical volcanic eruption in 1258, possibly of Mount Rinjani, followed by three smaller eruptions in 1268, 1275, and 1284 that did not allow the climate to recover, may have caused the initial cooling, and that the 1452–53 eruption of Kuwae in Vanuatu triggered a second pulse of cooling.[6][14] The cold summers can be maintained by sea-ice/ocean feedbacks long after volcanic aerosols are removed.
Other volcanoes that erupted during the era and may have contributed to the cooling include Billy Mitchell (ca. 1580), Huaynaputina (1600), Mount Parker (1641), Long Island (Papua New Guinea) (ca. 1660), and Laki (1783).[20]
The 1815 eruption of Tambora in Indonesia blanketed the atmosphere with ash; the following year, 1816, came to be known as the Year Without a Summer, when frost and snow were reported in June and July in both New England and Northern Europe.
