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Recent progress in understanding climate thresholds: Ice sheets, the Atlantic meridional overturning circulation, tropical forests and responses to ocean acidification

Recent progress in understanding climate thresholds: Ice sheets, the Atlantic meridional overturning circulation, tropical forests and responses to ocean acidification
Recent progress in understanding climate thresholds: Ice sheets, the Atlantic meridional overturning circulation, tropical forests and responses to ocean acidification

This article reviews recent scientific progress, relating to four major systems that could exhibit threshold behaviour: ice sheets, the Atlantic meridional overturning circulation (AMOC), tropical forests and ecosystem responses to ocean acidification. The focus is on advances since the Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC AR5). The most significant developments in each component are identified by synthesizing input from multiple experts from each field. For ice sheets, some degree of irreversible loss (timescales of millennia) of part of the West Antarctic Ice Sheet (WAIS) may have already begun, but the rate and eventual magnitude of this irreversible loss is uncertain. The observed AMOC overturning has decreased from 2004–2014, but it is unclear at this stage whether this is forced or is internal variability. New evidence from experimental and natural droughts has given greater confidence that tropical forests are adversely affected by drought. The ecological and socio-economic impacts of ocean acidification are expected to greatly increase over the range from today’s annual value of around 400, up to 650 ppm CO2 in the atmosphere (reached around 2070 under RCP8.5), with the rapid development of aragonite undersaturation at high latitudes affecting calcifying organisms. Tropical coral reefs are vulnerable to the interaction of ocean acidification and temperature rise, and the rapidity of those changes, with severe losses and risks to survival at 2 °C warming above pre-industrial levels. Across the four systems studied, however, quantitative evidence for a difference in risk between 1.5 and 2 °C warming above pre-industrial levels is limited.

Atlantic meridional overturning circulation, climate change, ice sheets, ocean acidification, thresholds, tropical forests
0309-1333
24-60
Good, Peter
45adcd89-872b-474e-b4df-3654b4eac2b7
Bamber, Jonathan
c69add5c-713c-4c4d-8035-fd02fa8ebd9a
Halladay, Kate
f5908ffe-1b1f-4063-b855-ccab3c352669
Harper, Anna B.
f21108a9-5bf9-4368-8d8c-5ab9e8517912
Jackson, Laura C.
c610e2ea-b151-4317-b44b-f4ac7a7e2070
Kay, Gillian
f9eb6fb9-cc5a-4bac-8a6b-da8d778bb400
Kruijt, Bart
ffe1924e-e1ad-4f58-a059-6383c2d57f24
Lowe, Jason A.
71d119ba-774f-493e-b5d7-18694f2bdc76
Phillips, Oliver L.
5ba6da16-abed-4be0-a1b1-3d1e9c53e071
Ridley, Jeff
ea3d3c4d-a40f-4ad9-af94-fafe355e07be
Srokosz, Meric
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Turley, Carol
9186da74-7bb6-4de7-844d-2a87c3a8598d
Williamson, Phillip
3bf73f38-ec5b-4e80-bbc3-3a2cc023770c
Good, Peter
45adcd89-872b-474e-b4df-3654b4eac2b7
Bamber, Jonathan
c69add5c-713c-4c4d-8035-fd02fa8ebd9a
Halladay, Kate
f5908ffe-1b1f-4063-b855-ccab3c352669
Harper, Anna B.
f21108a9-5bf9-4368-8d8c-5ab9e8517912
Jackson, Laura C.
c610e2ea-b151-4317-b44b-f4ac7a7e2070
Kay, Gillian
f9eb6fb9-cc5a-4bac-8a6b-da8d778bb400
Kruijt, Bart
ffe1924e-e1ad-4f58-a059-6383c2d57f24
Lowe, Jason A.
71d119ba-774f-493e-b5d7-18694f2bdc76
Phillips, Oliver L.
5ba6da16-abed-4be0-a1b1-3d1e9c53e071
Ridley, Jeff
ea3d3c4d-a40f-4ad9-af94-fafe355e07be
Srokosz, Meric
1e0442ce-679f-43f2-8fe4-9a0f0174d483
Turley, Carol
9186da74-7bb6-4de7-844d-2a87c3a8598d
Williamson, Phillip
3bf73f38-ec5b-4e80-bbc3-3a2cc023770c

Good, Peter, Bamber, Jonathan, Halladay, Kate, Harper, Anna B., Jackson, Laura C., Kay, Gillian, Kruijt, Bart, Lowe, Jason A., Phillips, Oliver L., Ridley, Jeff, Srokosz, Meric, Turley, Carol and Williamson, Phillip (2018) Recent progress in understanding climate thresholds: Ice sheets, the Atlantic meridional overturning circulation, tropical forests and responses to ocean acidification. Progress in Physical Geography, 42 (1), 24-60. (doi:10.1177/0309133317751843).

Record type: Article

Abstract

This article reviews recent scientific progress, relating to four major systems that could exhibit threshold behaviour: ice sheets, the Atlantic meridional overturning circulation (AMOC), tropical forests and ecosystem responses to ocean acidification. The focus is on advances since the Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC AR5). The most significant developments in each component are identified by synthesizing input from multiple experts from each field. For ice sheets, some degree of irreversible loss (timescales of millennia) of part of the West Antarctic Ice Sheet (WAIS) may have already begun, but the rate and eventual magnitude of this irreversible loss is uncertain. The observed AMOC overturning has decreased from 2004–2014, but it is unclear at this stage whether this is forced or is internal variability. New evidence from experimental and natural droughts has given greater confidence that tropical forests are adversely affected by drought. The ecological and socio-economic impacts of ocean acidification are expected to greatly increase over the range from today’s annual value of around 400, up to 650 ppm CO2 in the atmosphere (reached around 2070 under RCP8.5), with the rapid development of aragonite undersaturation at high latitudes affecting calcifying organisms. Tropical coral reefs are vulnerable to the interaction of ocean acidification and temperature rise, and the rapidity of those changes, with severe losses and risks to survival at 2 °C warming above pre-industrial levels. Across the four systems studied, however, quantitative evidence for a difference in risk between 1.5 and 2 °C warming above pre-industrial levels is limited.

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More information

e-pub ahead of print date: 7 February 2018
Published date: February 2018
Keywords: Atlantic meridional overturning circulation, climate change, ice sheets, ocean acidification, thresholds, tropical forests

Identifiers

Local EPrints ID: 420407
URI: http://eprints.soton.ac.uk/id/eprint/420407
ISSN: 0309-1333
PURE UUID: 755b1428-8e62-4a8d-ad2d-06fddf2263dc

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Date deposited: 04 May 2018 16:31
Last modified: 05 Jun 2024 19:58

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Contributors

Author: Peter Good
Author: Jonathan Bamber
Author: Kate Halladay
Author: Anna B. Harper
Author: Laura C. Jackson
Author: Gillian Kay
Author: Bart Kruijt
Author: Jason A. Lowe
Author: Oliver L. Phillips
Author: Jeff Ridley
Author: Meric Srokosz
Author: Carol Turley
Author: Phillip Williamson

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