Temperature-driven global sea-level variability in the Common Era

Robert E. Kopp; Andrew C. Kemp; Klaus Bittermann; Benjamin P. Horton; Jeffrey P. Donnelly; W. Roland Gehrels; Carling C. Hay; Jerry X. Mitrovica; Eric D. Morrow; Stefan Rahmstorf

doi:10.1073/pnas.1517056113

New Research In

Edited by Anny Cazenave, Centre National d'Etudes Spatiales, Toulouse, France, and approved January 4, 2016 (received for review August 27, 2015)

This article has a correction. Please see:

Correction for Kopp et al., Temperature-driven global sea-level variability in the Common Era

Significance

We present the first, to our knowledge, estimate of global sea-level (GSL) change over the last ∼3,000 years that is based upon statistical synthesis of a global database of regional sea-level reconstructions. GSL varied by ∼±8 cm over the pre-Industrial Common Era, with a notable decline over 1000–1400 CE coinciding with ∼0.2 °C of global cooling. The 20th century rise was extremely likely faster than during any of the 27 previous centuries. Semiempirical modeling indicates that, without global warming, GSL in the 20th century very likely would have risen by between −3 cm and +7 cm, rather than the ∼14 cm observed. Semiempirical 21st century projections largely reconcile differences between Intergovernmental Panel on Climate Change projections and semiempirical models.

Abstract

We assess the relationship between temperature and global sea-level (GSL) variability over the Common Era through a statistical metaanalysis of proxy relative sea-level reconstructions and tide-gauge data. GSL rose at 0.1 ± 0.1 mm/y (2σ) over 0–700 CE. A GSL fall of 0.2 ± 0.2 mm/y over 1000–1400 CE is associated with ∼0.2 °C global mean cooling. A significant GSL acceleration began in the 19th century and yielded a 20th century rise that is extremely likely (probability P≥0.95) faster than during any of the previous 27 centuries. A semiempirical model calibrated against the GSL reconstruction indicates that, in the absence of anthropogenic climate change, it is extremely likely (P=0.95) that 20th century GSL would have risen by less than 51% of the observed 13.8±1.5 cm. The new semiempirical model largely reconciles previous differences between semiempirical 21st century GSL projections and the process model-based projections summarized in the Intergovernmental Panel on Climate Change’s Fifth Assessment Report.

Footnotes

↵¹To whom correspondence should be addressed. Email: robert.kopp{at}rutgers.edu.

Author contributions: R.E.K. designed research; R.E.K., A.C.K., K.B., B.P.H., J.P.D., and W.R.G. performed research; R.E.K., K.B., C.C.H., J.X.M., E.D.M., and S.R. contributed new analytic tools; R.E.K. and K.B. analyzed data; R.E.K., A.C.K., K.B., B.P.H., J.P.D., W.R.G., C.C.H., J.X.M., E.D.M., and S.R. wrote the paper; A.C.K., B.P.H., and W.R.G. compiled the database of proxy reconstructions; C.C.H., J.X.M., and E.D.M. contributed to the design of the statistical model; and K.B. and S.R. developed and implemented the semiempirical projections.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1517056113/-/DCSupplemental.

Freely available online through the PNAS open access option.

Robert E. Kopp^a,^b,^c,¹,
Andrew C. Kemp^d,
Klaus Bittermann^e,
Benjamin P. Horton^b,^f,^g,^h,
Jeffrey P. Donnellyⁱ,
W. Roland Gehrels^j,
Carling C. Hay^a,^b,^k,
Jerry X. Mitrovica^k,
Eric D. Morrow^a,^b, and
Stefan Rahmstorf^e

^aDepartment of Earth & Planetary Sciences, Rutgers University, Piscataway, NJ 08854;
^bInstitute of Earth, Ocean & Atmospheric Sciences, Rutgers University, New Brunswick, NJ 08901;
^cRutgers Energy Institute, Rutgers University, New Brunswick, NJ 08901;
^dDepartment of Earth & Ocean Sciences, Tufts University, Medford, MA 02115;
^eEarth System Analysis, Potsdam Institute for Climate Impact Research, 14473 Potsdam, Germany;
^fSea-Level Research, Department of Marine & Coastal Sciences, Rutgers University, New Brunswick, NJ 08901;
^gEarth Observatory of Singapore, Nanyang Technological University, Singapore 639798;
^hAsian School of the Environment, Nanyang Technological University, Singapore 639798;
ⁱDepartment of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543;
^jEnvironment Department, University of York, York YO10 5NG, United Kingdom;
^kDepartment of Earth & Planetary Sciences, Harvard University, Cambridge, MA 02138

Edited by Anny Cazenave, Centre National d'Etudes Spatiales, Toulouse, France, and approved January 4, 2016 (received for review August 27, 2015)

Significance

Abstract

We assess the relationship between temperature and global sea-level (GSL) variability over the Common Era through a statistical metaanalysis of proxy relative sea-level reconstructions and tide-gauge data. GSL rose at 0.1 ± 0.1 mm/y (2σ) over 0–700 CE. A GSL fall of 0.2 ± 0.2 mm/y over 1000–1400 CE is associated with ∼0.2 °C global mean cooling. A significant GSL acceleration began in the 19th century and yielded a 20th century rise that is extremely likely (probability $P \geq 0.95$ ) faster than during any of the previous 27 centuries. A semiempirical model calibrated against the GSL reconstruction indicates that, in the absence of anthropogenic climate change, it is extremely likely ( $P = 0.95$ ) that 20th century GSL would have risen by less than 51% of the observed $13.8 \pm 1.5$ cm. The new semiempirical model largely reconciles previous differences between semiempirical 21st century GSL projections and the process model-based projections summarized in the Intergovernmental Panel on Climate Change’s Fifth Assessment Report.

sea level
Common Era
late Holocene
climate
ocean

Footnotes

↵¹To whom correspondence should be addressed. Email: robert.kopp{at}rutgers.edu.

Author contributions: R.E.K. designed research; R.E.K., A.C.K., K.B., B.P.H., J.P.D., and W.R.G. performed research; R.E.K., K.B., C.C.H., J.X.M., E.D.M., and S.R. contributed new analytic tools; R.E.K. and K.B. analyzed data; R.E.K., A.C.K., K.B., B.P.H., J.P.D., W.R.G., C.C.H., J.X.M., E.D.M., and S.R. wrote the paper; A.C.K., B.P.H., and W.R.G. compiled the database of proxy reconstructions; C.C.H., J.X.M., and E.D.M. contributed to the design of the statistical model; and K.B. and S.R. developed and implemented the semiempirical projections.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1517056113/-/DCSupplemental.

Freely available online through the PNAS open access option.

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