Last phase of the Little Ice Age forced by volcanic eruptions

• Published in: Nature geoscience Vol. 12; no. 8; pp. 650 - 656
• Main Authors: Brönnimann, Stefan, Franke, Jörg, Nussbaumer, Samuel U., Zumbühl, Heinz J., Steiner, Daniel, Trachsel, Mathias, Hegerl, Gabriele C., Schurer, Andrew, Worni, Matthias, Malik, Abdul, Flückiger, Julian, Raible, Christoph C.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-08-2019; Nature Publishing Group
• Subjects: 704/106/35; 704/106/413; 704/106/694; 704/106/829; Anthropogenic factors; Climate; Climate effects; Climate models; Climate system; Computer simulation; Drought; Earth and Environmental Science; Earth Sciences; Earth System Sciences; Geochemistry; Geology; Geophysics/Geodesy; Glaciers; Global climate; Heat exchange; Ice ages; Little Ice Age; Low pressure; Low temperature; Mountain glaciers; Northern Hemisphere; Precipitation; Sequencing; Three dimensional models; Tropical climate; Volcanic eruptions
• ISSN: 1752-0894; 1752-0908
• DOI: 10.1038/s41561-019-0402-y

During the first half of the nineteenth century, several large tropical volcanic eruptions occurred within less than three decades. The global climate effects of the 1815 Tambora eruption have been investigated, but those of an eruption in 1808 or 1809 whose source is unknown and the eruptions in the 1820s and 1830s have received less attention. Here we analyse the effect of the sequence of eruptions in observations, global three-dimensional climate field reconstructions and coupled climate model simulations. All the eruptions were followed by substantial drops of summer temperature over the Northern Hemisphere land areas. In addition to the direct radiative effect, which lasts 2–3 years, the simulated ocean–atmosphere heat exchange sustained cooling for several years after these eruptions, which affected the slow components of the climate system. Africa was hit by two decades of drought, global monsoons weakened and the tracks of low-pressure systems over the North Atlantic moved south. The low temperatures and increased precipitation in Europe triggered the last phase of the advance of Alpine glaciers. Only after the 1850s did the transition into the period of anthropogenic warming start. We conclude that the end of the Little Ice Age was marked by the recovery from a sequence of volcanic eruptions, which makes it difficult to define a single pre-industrial baseline.
Large volcanic eruptions in the first half of the nineteenth century blurred the transition from the Little Ice Age to anthropogenic warming, and led to sustained cooling, drought in Africa and weakened monsoons, suggests a combination of observations and model simulations.