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A. S. von der Heydt

Bio: A. S. von der Heydt is an academic researcher from Utrecht University. The author has contributed to research in topics: Climate sensitivity & Glacial period. The author has an hindex of 14, co-authored 23 publications receiving 964 citations.

Papers
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Journal ArticleDOI
TL;DR: Evidence relevant to Earth's equilibrium climate sensitivity per doubling of atmospheric CO2, characterized by an effective sensitivity S, is assessed, using a Bayesian approach to produce a probability density function for S given all the evidence, and promising avenues for further narrowing the range are identified.
Abstract: We assess evidence relevant to Earth's equilibrium climate sensitivity per doubling of atmospheric CO2, characterized by an effective sensitivity S. This evidence includes feedback process understanding, the historical climate record, and the paleoclimate record. An S value lower than 2 K is difficult to reconcile with any of the three lines of evidence. The amount of cooling during the Last Glacial Maximum provides strong evidence against values of S greater than 4.5 K. Other lines of evidence in combination also show that this is relatively unlikely. We use a Bayesian approach to produce a probability density function (PDF) for S given all the evidence, including tests of robustness to difficult-to-quantify uncertainties and different priors. The 66% range is 2.6-3.9 K for our Baseline calculation and remains within 2.3-4.5 K under the robustness tests; corresponding 5-95% ranges are 2.3-4.7 K, bounded by 2.0-5.7 K (although such high-confidence ranges should be regarded more cautiously). This indicates a stronger constraint on S than reported in past assessments, by lifting the low end of the range. This narrowing occurs because the three lines of evidence agree and are judged to be largely independent and because of greater confidence in understanding feedback processes and in combining evidence. We identify promising avenues for further narrowing the range in S, in particular using comprehensive models and process understanding to address limitations in the traditional forcing-feedback paradigm for interpreting past changes.

480 citations

Journal Article
TL;DR: This work presents a stricter approach to improve intercomparison of palaeoclimate sensitivity estimates in a manner compatible with equilibrium projections for future climate change, and reveals a climate sensitivity over the past 65 million years of 0.3–1.9 at 95% or 68% probability.
Abstract: Many palaeoclimate studies have quantified pre-anthropogenic climate change to calculate climate sensitivity (equilibrium temperature change in response to radiative forcing change), but a lack of consistent methodologies produces a wide range of estimates and hinders comparability of results. Here we present a stricter approach, to improve intercomparison of palaeoclimate sensitivity estimates in a manner compatible with equilibrium projections for future climate change. Over the past 65 million years, this reveals a climate sensitivity (in K W−1 m2) of 0.3–1.9 or 0.6–1.3 at 95% or 68% probability, respectively. The latter implies a warming of 2.2–4.8 K per doubling of atmospheric CO2, which agrees with IPCC estimates.

233 citations

Journal ArticleDOI
28 Nov 2012-Nature
TL;DR: In this article, a stricter approach was proposed to improve intercomparison of palaeoclimate sensitivity estimates in a manner compatible with equilibrium projections for future climate change, which revealed a climate sensitivity (in K W -1 m 2) of 0.3-1.9 or 0.6 -1.3 at 95% or 68% probability, respectively.
Abstract: Many palaeoclimate studies have quantified pre-anthropogenic climate change to calculate climate sensitivity (equilibrium temperature change in response to radiative forcing change), but a lack of consistent methodologies produces a wide range of estimates and hinders comparability of results. Here we present a stricter approach, to improve intercomparison of palaeoclimate sensitivity estimates in a manner compatible with equilibrium projections for future climate change. Over the past 65 million years, this reveals a climate sensitivity (in K W -1 m 2) of 0.3-1.9 or 0.6-1.3 at 95% or 68% probability, respectively. The latter implies a warming of 2.2-4.8 K per doubling of atmospheric CO 2, which agrees with IPCC estimates. © 2012 Macmillan Publishers Limited. All rights reserved.

228 citations

Journal ArticleDOI
01 May 2021
TL;DR: In this article, the authors synthesize several Miocene climate modeling efforts together with available terrestrial and ocean surface temperature reconstructions and evaluate the range of model-data agreement, highlight robust mechanisms operating across Miocene modeling efforts and highlight regions where differences across experiments result in a large spread in warming responses.
Abstract: The Miocene epoch, spanning 23.03–5.33 Ma, was a dynamic climate of sustained, polar amplified warmth. Miocene atmospheric CO2 concentrations are typically reconstructed between 300 and 600 ppm and were potentially higher during the Miocene Climatic Optimum (16.75–14.5 Ma). With surface temperature reconstructions pointing to substantial midlatitude and polar warmth, it is unclear what processes maintained the much weaker-than-modern equator-to-pole temperature difference. Here, we synthesize several Miocene climate modeling efforts together with available terrestrial and ocean surface temperature reconstructions. We evaluate the range of model-data agreement, highlight robust mechanisms operating across Miocene modeling efforts and regions where differences across experiments result in a large spread in warming responses. Prescribed CO2 is the primary factor controlling global warming across the ensemble. On average, elements other than CO2, such as Miocene paleogeography and ice sheets, raise global mean temperature by ∼2°C, with the spread in warming under a given CO2 concentration (due to a combination of the spread in imposed boundary conditions and climate feedback strengths) equivalent to ∼1.2 times a CO2 doubling. This study uses an ensemble of opportunity: models, boundary conditions, and reference data sets represent the state-of-art for the Miocene, but are inhomogeneous and not ideal for a formal intermodel comparison effort. Acknowledging this caveat, this study is nevertheless the first Miocene multi-model, multi-proxy comparison attempted so far. This study serves to take stock of the current progress toward simulating Miocene warmth while isolating remaining challenges that may be well served by community-led efforts to coordinate modeling and data activities within a common analytical framework.

72 citations

Journal ArticleDOI
TL;DR: In this paper, sub-surface signatures of the Atlantic Multidecadal Oscillation (AMO) were identified using expendable bathythermograph (XBT) measurements of temperature from the surface down to a depth of 400 m.
Abstract: [1] Sub-surface signatures of the Atlantic Multidecadal Oscillation (AMO) are identified using expendable bathythermograph (XBT) measurements of temperature from the surface down to a depth of 400 m. Basin averaged temperature anomalies in the North Atlantic at different depths display multidecadal variability with a phase shift between temperature anomalies at the surface and at depth. Westward propagation of temperature anomalies is observable at depth and there is a lag correlation between east-west and north-south temperature gradients, with the east-west temperature gradient leading. These sub-surface characteristics of the AMO agree with those expected from the noise-driven internal ocean mode view of the AMO, as derived from a hierarchy of ocean-atmosphere models.

49 citations


Cited by
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Book Chapter
01 Jan 2013
TL;DR: The authors assesses long-term projections of climate change for the end of the 21st century and beyond, where the forced signal depends on the scenario and is typically larger than the internal variability of the climate system.
Abstract: This chapter assesses long-term projections of climate change for the end of the 21st century and beyond, where the forced signal depends on the scenario and is typically larger than the internal variability of the climate system. Changes are expressed with respect to a baseline period of 1986-2005, unless otherwise stated.

2,253 citations

01 Dec 2007
TL;DR: It is shown that the breadth of the distribution and, in particular, the probability of large temperature increases are relatively insensitive to decreases in uncertainties associated with the underlying climate processes.
Abstract: Uncertainties in projections of future climate change have not lessened substantially in past decades. Both models and observations yield broad probability distributions for long-term increases in global mean temperature expected from the doubling of atmospheric carbon dioxide, with small but finite probabilities of very large increases. We show that the shape of these probability distributions is an inevitable and general consequence of the nature of the climate system, and we derive a simple analytic form for the shape that fits recent published distributions very well. We show that the breadth of the distribution and, in particular, the probability of large temperature increases are relatively insensitive to decreases in uncertainties associated with the underlying climate processes.

540 citations

Journal ArticleDOI
03 Dec 2013-PLOS ONE
TL;DR: Climate impacts of global warming is assessed using ongoing observations and paleoclimate data and simple representations of the global carbon cycle and temperature to define emission reductions needed to stabilize climate and avoid potentially disastrous impacts on today’s young people, future generations, and nature.
Abstract: We assess climate impacts of global warming using ongoing observations and paleoclimate data. We use Earth's measured energy imbalance, paleoclimate data, and simple representations of the global carbon cycle and temperature to define emission reductions needed to stabilize climate and avoid potentially disas- trous impacts on today's young people, future genera- tions, and nature. A cumulative industrial-era limit of ,500 GtC fossil fuel emissions and 100 GtC storage in the biosphere and soil would keep climate close to the Holocene range to which humanity and other species are adapted. Cumulative emissions of ,1000 GtC, sometimes associated with 2uC global warming, would spur ''slow'' feedbacks and eventual warming of 3-4uC with disastrous consequences. Rapid emissions reduction is required to restore Earth's energy balance and avoid ocean heat uptake that would practically guarantee irreversible effects. Continuation of high fossil fuel emissions, given current knowledge of the consequences, would be an act of extraordinary witting intergenerational injustice. Re- sponsible policymaking requires a rising price on carbon emissions that would preclude emissions from most remaining coal and unconventional fossil fuels and phase down emissions from conventional fossil fuels.

508 citations

Journal ArticleDOI
02 Aug 2013-Science
TL;DR: The likelihood of continued changes in terrestrial climate is reviewed, including analyses of the Coupled Model Intercomparison Project global climate model ensemble, to create potential 21st-century global warming comparable in magnitude to that of the largest global changes in the past 65 million years but is orders of magnitude more rapid.
Abstract: Terrestrial ecosystems have encountered substantial warming over the past century, with temperatures increasing about twice as rapidly over land as over the oceans. Here, we review the likelihood of continued changes in terrestrial climate, including analyses of the Coupled Model Intercomparison Project global climate model ensemble. Inertia toward continued emissions creates potential 21st-century global warming that is comparable in magnitude to that of the largest global changes in the past 65 million years but is orders of magnitude more rapid. The rate of warming implies a velocity of climate change and required range shifts of up to several kilometers per year, raising the prospect of daunting challenges for ecosystems, especially in the context of extensive land use and degradation, changes in frequency and severity of extreme events, and interactions with other stresses.

497 citations

Journal ArticleDOI
TL;DR: Evidence relevant to Earth's equilibrium climate sensitivity per doubling of atmospheric CO2, characterized by an effective sensitivity S, is assessed, using a Bayesian approach to produce a probability density function for S given all the evidence, and promising avenues for further narrowing the range are identified.
Abstract: We assess evidence relevant to Earth's equilibrium climate sensitivity per doubling of atmospheric CO2, characterized by an effective sensitivity S. This evidence includes feedback process understanding, the historical climate record, and the paleoclimate record. An S value lower than 2 K is difficult to reconcile with any of the three lines of evidence. The amount of cooling during the Last Glacial Maximum provides strong evidence against values of S greater than 4.5 K. Other lines of evidence in combination also show that this is relatively unlikely. We use a Bayesian approach to produce a probability density function (PDF) for S given all the evidence, including tests of robustness to difficult-to-quantify uncertainties and different priors. The 66% range is 2.6-3.9 K for our Baseline calculation and remains within 2.3-4.5 K under the robustness tests; corresponding 5-95% ranges are 2.3-4.7 K, bounded by 2.0-5.7 K (although such high-confidence ranges should be regarded more cautiously). This indicates a stronger constraint on S than reported in past assessments, by lifting the low end of the range. This narrowing occurs because the three lines of evidence agree and are judged to be largely independent and because of greater confidence in understanding feedback processes and in combining evidence. We identify promising avenues for further narrowing the range in S, in particular using comprehensive models and process understanding to address limitations in the traditional forcing-feedback paradigm for interpreting past changes.

480 citations