Nonlinear climate sensitivity and its implications for future greenhouse warming

Friedrich, Tobias; Timmermann, Axel; Tigchelaar, Michelle; Timm, O. Elison; Ganopolski, Andrey

doi:10.1126/sciadv.1501923

Cited by 139 publications

(148 citation statements)

References 102 publications

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“…modelled global temperature (De Boer et al, 2014, scaled). Friedrich et al (2016) forced the intermediate complexity climate model LOVECLIM over the past 800 kyr using the ice core record (Petit et al, 1999;Siegenthaler et al, 2005;Lüthi et al, 2008) and a Northern Hemisphere ice sheet reconstruction (Ganopolski and Calov, 2011). The resulting climate sensitivity of these studies is opposite to ours, as they show increased climate sensitivity at higher CO 2 concentrations.…”

Section: Results and Discussion Ii: Ice Sheet-climate Interactioncontrasting

confidence: 52%

“…Therefore, decreased sensitivity at higher CO 2 is not only determined by reduced ice volume variability. This finding may be compared to the hybrid data-model results for climate sensitivity of Köhler et al (2015) and to the modelled climate sensitivity of Friedrich et al (2016). Köhler et al (2015) investigated the relation between the radiative forcing of proxy data CO 2 (Petit et al, 1999;Siegenthaler et al, 2005;Lüthi et al, 2008;Hönisch et al, 2009), which is linearly related to logarithmic CO 2 (Myhre et al, 1998), and Figure 8.…”

Section: Results and Discussion Ii: Ice Sheet-climate Interactionmentioning

confidence: 99%

“…Stomata-based data (Van der Burgh et al, 1993;Kürschner, 1996;Kürschner et al, 2008;Retallack, 2009) Pliocene (3.5 to 2.5 Myr ago), the Middle Miocene (18 to 13 Myr ago), and the Early Oligocene (35 to 30 Myr ago). The data are based on three important proxies (see also Beerling and Royer, 2011): alkenones (Pagani et al, 1999(Pagani et al, , 2011Badger et al, 2013), boron isotopes (Pearson et al, 2009;Foster et al, 2012;Greenop et al, 2014;Martínez-Botí et al, 2015), and stomata (Van der Burgh et al, 1993;Kürschner, 1996;Kürschner et al, 2008;Retallack, 2009). During the Late Pliocene, the simulated CO 2 is more variable than the alkenone data from Badger et al (2013) (Fig.…”

Section: Comparison To Proxy Co 2 Datamentioning

confidence: 99%

“…5 we show the new reference CO 2 results together with proxy data over three periods for which data are relatively abundant: the Late (Pagani et al, 1999(Pagani et al, , 2011Badger et al, 2013) are indicated by orange asterisks. Boron-isotope-based data (Pearson et al, 2009;Foster et al, 2012;Greenop et al, 2014;Martínez-Botí et al, 2015) are indicated by blue plus symbols. Stomata-based data (Van der Burgh et al, 1993;Kürschner, 1996;Kürschner et al, 2008;Retallack, 2009) Pliocene (3.5 to 2.5 Myr ago), the Middle Miocene (18 to 13 Myr ago), and the Early Oligocene (35 to 30 Myr ago).…”

Section: Comparison To Proxy Co 2 Datamentioning

confidence: 99%

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The influence of ice sheets on temperature during the past 38 million years inferred from a one-dimensional ice sheet–climate model

et al. 2017

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Abstract. Since the inception of the Antarctic ice sheet at the Eocene-Oligocene transition ( ∼ 34 Myr ago), land ice has played a crucial role in Earth's climate. Through feedbacks in the climate system, land ice variability modifies atmospheric temperature changes induced by orbital, topographical, and greenhouse gas variations. Quantification of these feedbacks on long timescales has hitherto scarcely been undertaken. In this study, we use a zonally averaged energy balance climate model bidirectionally coupled to a one-dimensional ice sheet model, capturing the ice-albedo and surface-height-temperature feedbacks. Potentially important transient changes in topographic boundary conditions by tectonics and erosion are not taken into account but are briefly discussed. The relative simplicity of the coupled model allows us to perform integrations over the past 38 Myr in a fully transient fashion using a benthic oxygen isotope record as forcing to inversely simulate CO 2 . Firstly, we find that the results of the simulations over the past 5 Myr are dependent on whether the model run is started at 5 or 38 Myr ago. This is because the relation between CO 2 and temperature is subject to hysteresis. When the climate cools from very high CO 2 levels, as in the longer transient 38 Myr run, temperatures in the lower CO 2 range of the past 5 Myr are higher than when the climate is initialised at low temperatures. Consequently, the modelled CO 2 concentrations depend on the initial state. Taking the realistic warm initialisation into account, we come to a best estimate of CO 2 , temperature, ice-volume-equivalent sea level, and benthic δ 18 O over the past 38 Myr. Secondly, we study the influence of ice sheets on the evolution of global temperature and polar amplification by comparing runs with ice sheet-climate interaction switched on and off. By passing only albedo or surface height changes to the climate model, we can distinguish the separate effects of the ice-albedo and surfaceheight-temperature feedbacks. We find that ice volume variability has a strong enhancing effect on atmospheric temperature changes, particularly in the regions where the ice sheets are located. As a result, polar amplification in the Northern Hemisphere decreases towards warmer climates as there is little land ice left to melt. Conversely, decay of the Antarctic ice sheet increases polar amplification in the Southern Hemisphere in the high-CO 2 regime. Our results also show that in cooler climates than the pre-industrial, the ice-albedo feedback predominates the surface-heighttemperature feedback, while in warmer climates they are more equal in strength.

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Section: Results and Discussion Ii: Ice Sheet-climate Interactioncontrasting

confidence: 52%

Section: Results and Discussion Ii: Ice Sheet-climate Interactionmentioning

confidence: 99%

Section: Comparison To Proxy Co 2 Datamentioning

confidence: 99%

Section: Comparison To Proxy Co 2 Datamentioning

confidence: 99%

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The influence of ice sheets on temperature during the past 38 million years inferred from a one-dimensional ice sheet–climate model

et al. 2017

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“…First, temporal changes in the radiative balance of climate are important because ice masses have high albedo and reflect incoming solar radiation (e.g., Hansen et al, 2007Hansen et al, , 2008K€ ohler et al, 2010, 2015Rohling et al, 2012;PALAEOSENS project members, 2012;Martínez-Botí et al, 2015;Friedrich et al, 2016). Second, temporal development of ice-age cycles provides critical information about the nature of long-term climate cooling over the past few million years, in response to CO 2 reduction and interactions among ice, land cover, and climate (e.g., Clark et al, 2006;K€ ohler and Bintanja, 2008;de Boer et al, 2010de Boer et al, , 2012Hansen et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Differences between the last two glacial maxima and implications for ice-sheet, δ18O, and sea-level reconstructions

Rohling

Hibbert

Williams

et al. 2017

Quaternary Science Reviews

100

115

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Arctic ice shelf Last Interglacial Glacioisostatic adjustment a b s t r a c t Studies of past glacial cycles yield critical information about climate and sea-level (ice-volume) variability, including the sensitivity of climate to radiative change, and impacts of crustal rebound on sealevel reconstructions for past interglacials. Here we identify significant differences between the last and penultimate glacial maxima (LGM and PGM) in terms of global volume and distribution of land ice, despite similar temperatures and radiative forcing. Our analysis challenges conventional views of relationships between global ice volume, sea level, seawater oxygen isotope values, and deep-sea temperature, and supports the potential presence of large floating Arctic ice shelves during the PGM. The existence of different glacial 'modes' calls for focussed research on the complex processes behind ice-age development. We present a glacioisostatic assessment to demonstrate how a different PGM ice-sheet configuration might affect sea-level estimates for the last interglacial. Results suggest that this may alter existing last interglacial sea-level estimates, which often use an LGM-like ice configuration, by several metres (likely upward).

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State‐Dependence of the Climate Sensitivity in Earth System Models of Intermediate Complexity

Pfister

Stocker

2017

Geophysical Research Letters

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Growing evidence from general circulation models (GCMs) indicates that the equilibrium climate sensitivity (ECS) depends on the magnitude of forcing, which is commonly referred to as state‐dependence. We present a comprehensive assessment of ECS state‐dependence in Earth system models of intermediate complexity (EMICs) by analyzing millennial simulations with sustained 2×CO2 and 4×CO2 forcings. We compare different extrapolation methods and show that ECS is smaller in the higher‐forcing scenario in 12 out of 15 EMICs, in contrast to the opposite behavior reported from GCMs. In one such EMIC, the Bern3D‐LPX model, this state‐dependence is mainly due to the weakening sea ice‐albedo feedback in the Southern Ocean, which depends on model configuration. Due to ocean‐mixing adjustments, state‐dependence is only detected hundreds of years after the abrupt forcing, highlighting the need for long model integrations. Adjustments to feedback parametrizations of EMICs may be necessary if GCM intercomparisons confirm an opposite state‐dependence.

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Nonlinear climate sensitivity and its implications for future greenhouse warming

Abstract: Climate sensitivity reconstructed from eight glacial cycles exhibits state dependence and confirms global warming projections.

Cited by 139 publications

References 102 publications

The influence of ice sheets on temperature during the past 38 million years inferred from a one-dimensional ice sheet–climate model

The influence of ice sheets on temperature during the past 38 million years inferred from a one-dimensional ice sheet–climate model

Differences between the last two glacial maxima and implications for ice-sheet, δ18O, and sea-level reconstructions

State‐Dependence of the Climate Sensitivity in Earth System Models of Intermediate Complexity

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