sulfur dioxide yield and 23 or 26–55 million tons for the sulfur. In Antarctica the sulfur yield was estimated to be about one-third that of the 1815 Tambora eruption, although the climate impact in the Northern Hemisphere might have been aggravated by the distribution of the aerosols; at one Antarctic site the Huaynaputina sulfate layer is thicker than the one from Tambora. Inferences from rock composition usually yield a higher sulfur output than ice core data; this may reflect either ice cores underestimating the amount of sulfur erupted as ice cores only record stratospheric sulfur, ice cores underestimating the amount of sulfur for other reasons or overestimating the amount of sulfur contained within magma-associated fluids. The Huaynaputina eruption was probably unusually rich in sulfur compared to its volume. A large amount of sulfur appears to have been carried in a volatile phase associated with the magma rather than in the magma proper. An even larger amount of sulfur may have originated from a relic hydrothermal system that underpins the volcano, and whose accumulated sulfur would have been mobilized by the 1600 eruption; some contradictions between the sulfur yield inferred from ice core data and these inferred from the magma composition can be resolved this way. Atmospheric carbon dioxide concentrations in 1610 decreased for reasons unknown; high mortality in the Americas after the European arrival may be the reason, but this decrease could have been at least in part the consequence of the Huaynaputina eruption. The vast tephra fallout of the eruption fell in part over the sea; the fertilizing effect of the tephra may have induced a draw-down of carbon dioxide from the atmosphere. Climate impacts Volcanic eruptions alter worldwide climate by injecting ash and gases into the atmosphere, which reduce the amount of sunlight reaching the Earth, often causing cold weather and crop failures. The Huaynaputina eruption decreased the amount on solar energy reaching Earth by about The summer of 1601 was among the coldest in the Northern Hemisphere during the last six centuries, and the impact may have been comparable to that of the 1815 Tambora, 1452/1453 mystery eruption, 1257 Samalas and 536 Ilopango eruptions. The eruption is thought to have caused a volcanic winter. Other volcanoes may have erupted alongside Huaynaputina and also contributed to the weather anomalies; several large volcanic eruptions took place in the decades preceding and following the Huaynaputina eruption. The eruption had a