The oceans mediate the response of global climate to natural and anthropogenic forcings. Yet for the past 2,000 years — a key interval for understanding the present and future climate response to these forcings — global sea surface temperature changes and the underlying driving mechanisms are poorly constrained. Here we present a global synthesis of sea surface temperatures for the Common Era (ce) derived from 57 individual marine reconstructions that meet strict quality control criteria. We observe a cooling trend from 1 to 1800 ce that is robust against explicit tests for potential biases in the reconstructions. Between 801 and 1800 ce, the surface cooling trend is qualitatively consistent with an independent synthesis of terrestrial temperature reconstructions, and with a sea surface temperature composite derived from an ensemble of climate model simulations using best estimates of past external radiative forcings. Climate simulations using single and cumulative forcings suggest that the ocean surface cooling trend from 801 to 1800 ce is not primarily a response to orbital forcing but arises from a high frequency of explosive volcanism. Our results show that repeated clusters of volcanic eruptions can induce a net negative radiative forcing that results in a centennial and global scale cooling trend via a decline in mixed-layer oceanic heat content.

Item Type:	Refereed Article
Keywords:	palaeoclimate, oceans, Common Era, natural forcings, anthropogenic forcings, climate models, volcanoes
Research Division:	Earth Sciences
Research Group:	Physical Geography and Environmental Geoscience
Research Field:	Palaeoclimatology
Objective Division:	Environment
Objective Group:	Climate and Climate Change
Objective Field:	Climate and Climate Change not elsewhere classified
UTAS Author:	Phipps, SJ (Dr Steven Phipps)
ID Code:	104738
Year Published:	2015
Web of Science® Times Cited:	95
Deposited By:	IMAS Research and Education Centre
Deposited On:	2015-11-18
Last Modified:	2017-10-30
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