An Assessment of Earth's Climate Sensitivity Using Multiple Lines of Evidence

Reviews of Geophysics, Journal Year: 2020, Volume and Issue: 58(4)

Published: July 22, 2020

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

Language: Английский

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Twenty-first century ocean warming, acidification, deoxygenation, and upper-ocean nutrient and primary production decline from CMIP6 model projections

Biogeosciences, Journal Year: 2020, Volume and Issue: 17(13), P. 3439 - 3470

Published: July 6, 2020

Abstract. Anthropogenic climate change is projected to lead ocean warming, acidification, deoxygenation, reductions in near-surface nutrients, and changes primary production, all of which are expected affect marine ecosystems. Here we assess projections these drivers environmental over the twenty-first century from Earth system models (ESMs) participating Coupled Model Intercomparison Project Phase 6 (CMIP6) that were forced under CMIP6 Shared Socioeconomic Pathways (SSPs). Projections compared those previous generation (CMIP5) Representative Concentration (RCPs). A total 10 CMIP5 13 used two multi-model ensembles. Under high-emission scenario SSP5-8.5, global mean (2080–2099 values relative 1870–1899) ± inter-model SD sea surface temperature, pH, subsurface (100–600 m) oxygen concentration, euphotic (0–100 nitrate depth-integrated production +3.47±0.78 ∘C, -0.44±0.005, -13.27±5.28, -1.06±0.45 mmol m−3 -2.99±9.11 %, respectively. low-emission, high-mitigation SSP1-2.6, corresponding +1.42±0.32 -0.16±0.002, -6.36±2.92, -0.52±0.23 m−3, -0.56±4.12 %. Projected exposure ecosystem depends largely on extent future emissions, consistent with studies. The ESMs generally project greater but lesser declines than comparable radiative forcing. increased warming results a general increase sensitivity CMIP5. This enhanced increases upper-ocean stratification projections, contributes ventilation. acidification primarily consequence SSPs having higher associated atmospheric CO2 concentrations their RCP analogues for same We find no reduction uncertainties, even an net uncertainties CMIP6, as

Language: Английский

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Context for interpreting equilibrium climate sensitivity and transient climate response from the CMIP6 Earth system models

Science Advances, Journal Year: 2020, Volume and Issue: 6(26)

Published: June 24, 2020

A historical context is provided for interpreting the equilibrium climate sensitivity (ECS) and transient response (TCR).

Language: Английский

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Past warming trend constrains future warming in CMIP6 models

Science Advances, Journal Year: 2020, Volume and Issue: 6(12)

Published: March 18, 2020

Strong future warming in some new climate models is less likely as their recent inconsistent with observed trends.

Language: Английский

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GISS‐E2.1: Configurations and Climatology

Journal of Advances in Modeling Earth Systems, Journal Year: 2020, Volume and Issue: 12(8)

Published: July 10, 2020

This paper describes the GISS-E2.1 contribution to Coupled Model Intercomparison Project, Phase 6 (CMIP6). model version differs from predecessor (GISS-E2) chiefly due parameterization improvements atmospheric and ocean components, while keeping resolution same. skill when compared modern era climatologies is significantly higher than in previous versions. Additionally, updates forcings have a material impact on results. In particular, there been specific representations of modes variability (such as Madden-Julian Oscillation other Pacific) significant simulation climate Southern Oceans, including sea ice. The effective sensitivity 2 × CO2 slightly previously at 2.7-3.1°C (depending version) result lower radiative forcing stronger positive feedbacks.

Language: Английский

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Climate change is increasing the likelihood of extreme autumn wildfire conditions across California

Environmental Research Letters, Journal Year: 2020, Volume and Issue: 15(9), P. 094016 - 094016

Published: March 30, 2020

Abstract California has experienced devastating autumn wildfires in recent years. These have coincided with extreme fire weather conditions during periods of strong offshore winds coincident unusually dry vegetation enabled by anomalously warm and late onset precipitation. In this study, we quantify observed changes the occurrence magnitude meteorological factors that enable California, use climate model simulations to ascertain whether these are attributable human-caused change. We show state-wide increases temperature (∼1 °C) decreases precipitation (∼30%) over past four decades contributed aggregate indices (+20%). As a result, frequency days (95th percentile) weather—which preferentially associated wildfires—has more than doubled since early 1980s. further find an increase model-estimated probability ∼1950, including long-term trend toward increased same-season co-occurrence northern southern California. Our analyses suggest continued change will amplify number end century, though pathway consistent UN Paris commitments would substantially curb increase. Given acute societal impacts years, our findings critical relevance for ongoing efforts manage wildfire risks other regions.

Language: Английский

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Projected land ice contributions to twenty-first-century sea level rise

Nature, Journal Year: 2021, Volume and Issue: 593(7857), P. 74 - 82

Published: May 5, 2021

Language: Английский

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Underestimating the Challenges of Avoiding a Ghastly Future

Frontiers in Conservation Science, Journal Year: 2021, Volume and Issue: 1

Published: Jan. 13, 2021

We report three major and confronting environmental issues that have received little attention require urgent action. First, we review the evidence future conditions will be far more dangerous than currently believed. The scale of threats to biosphere all its lifeforms — including humanity is in fact so great it difficult grasp for even well-informed experts. Second, ask what political or economic system, leadership, prepared handle predicted disasters, capable such Third, this dire situation places an extraordinary responsibility on scientists speak out candidly accurately when engaging with government, business, public. especially draw lack appreciation enormous challenges creating a sustainable future. added stresses human health, wealth, well-being perversely diminish our capacity mitigate erosion ecosystem services which society depends. science underlying these strong, but awareness weak. Without fully appreciating broadcasting problems enormity solutions required, fail achieve modest sustainability goals.

Language: Английский

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An update of IPCC climate reference regions for subcontinental analysis of climate model data: definition and aggregated datasets

Earth system science data, Journal Year: 2020, Volume and Issue: 12(4), P. 2959 - 2970

Published: Nov. 18, 2020

Abstract. Several sets of reference regions have been used in the literature for regional synthesis observed and modelled climate change information. A popular example is series Intergovernmental Panel on Climate Change (IPCC) Special Report Managing Risks Extreme Events Disasters to Advance Adaptation (SREX). The SREX were slightly modified Fifth Assessment IPCC reporting subcontinental projected changes over a reduced number (33) climatologically consistent encompassing representative grid boxes. These are intended allow analysis atmospheric data broad land or ocean as basis several spatially aggregated datasets, such Seasonal Mean Temperature Precipitation Regions CMIP5 dataset. We present an updated version new simulated datasets (including CMIP6) which offer opportunity refinement due higher model resolution. As result, increased 46 15, respectively, better representing features. paper describes rationale definition analyses their homogeneity. defined polygons provided coordinates shapefile together with companion R Python notebooks illustrate use practical problems (e.g. calculating averages). also describe generation dataset monthly temperature precipitation, regions, currently CMIP6, be extended other future observations). these code illustrated through worked using scatter plots guidance likely range at scale regions. (R notebooks) freely available ATLAS GitHub repository: https://github.com/SantanderMetGroup/ATLAS (last access: 24 August 2020), https://doi.org/10.5281/zenodo.3998463 (Iturbide et al., 2020).

Language: Английский

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Effective radiative forcing and adjustments in CMIP6 models

Atmospheric chemistry and physics, Journal Year: 2020, Volume and Issue: 20(16), P. 9591 - 9618

Published: Aug. 17, 2020

Abstract. The effective radiative forcing, which includes the instantaneous forcing plus adjustments from atmosphere and surface, has emerged as key metric of evaluating human natural influence on climate. We evaluate in 17 contemporary climate models that are participating Coupled Model Intercomparison Project (CMIP6) have contributed to Radiative Forcing (RFMIP). Present-day (2014) global-mean anthropogenic relative pre-industrial (1850) levels stands at 2.00 (±0.23) W m−2, comprised 1.81 (±0.09) m−2 CO2, 1.08 (± 0.21) other well-mixed greenhouse gases, −1.01 0.23) aerosols −0.09 (±0.13) land use change. Quoted uncertainties 1 standard deviation across model best estimates, 90 % confidence reported forcings, due internal variability, is typically within 0.1 m−2. majority remaining 0.21 likely be ozone. In most cases, largest contributors spread (ERF) (IRF) cloud responses, particularly aerosol–cloud interactions aerosol forcing. As determined previous studies, cancellation tropospheric surface means stratospherically adjusted approximately equal ERF for gas but not aerosols, consequentially, total. ranges −0.63 −1.37 exhibiting a less negative mean narrower range compared 10 CMIP5 models. 4×CO2 also narrowed CMIP6 13 Aerosol uncorrelated with sensitivity. Therefore, there no evidence suggest increasing sensitivity models, related high-sensitivity consequence stronger present-day little modelling groups systematically tuning or recreate observed historical warming.

Language: Английский

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