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Nicholls Z, Meinshausen M, Lewis J, Smith CJ, Forster PM, Fuglestvedt JS, Rogelj J, Kikstra JS, Riahi K, Byers E. Changes in IPCC Scenario Assessment Emulators Between SR1.5 and AR6 Unraveled. Geophys Res Lett 2022; 49:e2022GL099788. [PMID: 36589268 PMCID: PMC9788315 DOI: 10.1029/2022gl099788] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 09/29/2022] [Accepted: 10/05/2022] [Indexed: 06/17/2023]
Abstract
The IPCC's scientific assessment of the timing of net-zero emissions and 2030 emission reduction targets consistent with limiting warming to 1.5°C or 2°C rests on large scenario databases. Updates to this assessment, such as between the IPCC's Special Report on Global Warming of 1.5°C (SR1.5) of warming and the Sixth Assessment Report (AR6), are the result of intertwined, sometimes opaque, factors. Here we isolate one factor: the Earth System Model emulators used to estimate the global warming implications of scenarios. We show that warming projections using AR6-calibrated emulators are consistent, to within around 0.1°C, with projections made by the emulators used in SR1.5. The consistency is due to two almost compensating changes: the increase in assessed historical warming between SR1.5 (based on AR5) and AR6, and a reduction in projected warming due to improved agreement between the emulators' response to emissions and the assessment to which it is calibrated.
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Affiliation(s)
- Z. Nicholls
- International Institute for Applied System AnalysisIIASALaxenburgAustria
- Climate & Energy CollegeSchool of Geography, Earth and Atmospheric SciencesThe University of MelbourneParkvilleVICAustralia
- Climate ResourceNorthcoteVICAustralia
| | - M. Meinshausen
- Climate & Energy CollegeSchool of Geography, Earth and Atmospheric SciencesThe University of MelbourneParkvilleVICAustralia
- Climate ResourceNorthcoteVICAustralia
| | - J. Lewis
- International Institute for Applied System AnalysisIIASALaxenburgAustria
- Climate & Energy CollegeSchool of Geography, Earth and Atmospheric SciencesThe University of MelbourneParkvilleVICAustralia
- Climate ResourceNorthcoteVICAustralia
| | - C. J. Smith
- International Institute for Applied System AnalysisIIASALaxenburgAustria
- Priestley International Centre for ClimateUniversity of LeedsLeedsUK
| | - P. M. Forster
- Priestley International Centre for ClimateUniversity of LeedsLeedsUK
| | | | - J. Rogelj
- International Institute for Applied System AnalysisIIASALaxenburgAustria
- Centre for Environmental PolicyImperial College LondonLondonUK
- Grantham Institute for Climate Change and the EnvironmentImperial College LondonLondonUK
| | - J. S. Kikstra
- International Institute for Applied System AnalysisIIASALaxenburgAustria
- Centre for Environmental PolicyImperial College LondonLondonUK
- Grantham Institute for Climate Change and the EnvironmentImperial College LondonLondonUK
| | - K. Riahi
- International Institute for Applied System AnalysisIIASALaxenburgAustria
| | - E. Byers
- International Institute for Applied System AnalysisIIASALaxenburgAustria
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Samset BH, Zhou C, Fuglestvedt JS, Lund MT, Marotzke J, Zelinka MD. Earlier emergence of a temperature response to mitigation by filtering annual variability. Nat Commun 2022; 13:1578. [PMID: 35332146 PMCID: PMC8948247 DOI: 10.1038/s41467-022-29247-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 02/28/2022] [Indexed: 11/23/2022] Open
Abstract
The rate of global surface warming is crucial for tracking progress towards global climate targets, but is strongly influenced by interannual-to-decadal variability, which precludes rapid detection of the temperature response to emission mitigation. Here we use a physics based Green’s function approach to filter out modulations to global mean surface temperature from sea-surface temperature (SST) patterns, and show that it results in an earlier emergence of a response to strong emissions mitigation. For observed temperatures, we find a filtered 2011–2020 surface warming rate of 0.24 °C per decade, consistent with long-term trends. Unfiltered observations show 0.35 °C per decade, partly due to the El Nino of 2015–2016. Pattern filtered warming rates can become a strong tool for the climate community to inform policy makers and stakeholder communities about the ongoing and expected climate responses to emission reductions, provided an effort is made to improve and validate standardized Green’s functions. The pattern of sea surface temperatures affects global mean temperatures from year to year. By filtering out parts of this natural variability, researchers show that they can more rapidly detect the influence of mitigation of CO2 emissions on the climate
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Affiliation(s)
- B H Samset
- CICERO Center for International Climate Research, Oslo, Norway.
| | - C Zhou
- Nanjing University, Nanjing, China
| | - J S Fuglestvedt
- CICERO Center for International Climate Research, Oslo, Norway
| | - M T Lund
- CICERO Center for International Climate Research, Oslo, Norway
| | - J Marotzke
- Max Planck Institute for Meteorology, Hamburg, Germany and Center for Earth System Research and Sustainability, Universität Hamburg, Hamburg, Germany
| | - M D Zelinka
- Lawrence Livermore National Laboratory, Livermore, USA
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Hodnebrog Ø, Aamaas B, Fuglestvedt JS, Marston G, Myhre G, Nielsen CJ, Sandstad M, Shine KP, Wallington TJ. Updated Global Warming Potentials and Radiative Efficiencies of Halocarbons and Other Weak Atmospheric Absorbers. Rev Geophys 2020; 58:e2019RG000691. [PMID: 33015672 PMCID: PMC7518032 DOI: 10.1029/2019rg000691] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 06/26/2020] [Accepted: 07/06/2020] [Indexed: 05/10/2023]
Abstract
Human activity has led to increased atmospheric concentrations of many gases, including halocarbons, and may lead to emissions of many more gases. Many of these gases are, on a per molecule basis, powerful greenhouse gases, although at present-day concentrations their climate effect is in the so-called weak limit (i.e., their effect scales linearly with concentration). We published a comprehensive review of the radiative efficiencies (RE) and global warming potentials (GWP) for around 200 such compounds in 2013 (Hodnebrog et al., 2013, https://doi.org/10.1002/rog.20013). Here we present updated RE and GWP values for compounds where experimental infrared absorption spectra are available. Updated numbers are based on a revised "Pinnock curve", which gives RE as a function of wave number, and now also accounts for stratospheric temperature adjustment (Shine & Myhre, 2020, https://doi.org/10.1029/2019MS001951). Further updates include the implementation of around 500 absorption spectra additional to those in the 2013 review and new atmospheric lifetimes from the literature (mainly from WMO (2019)). In total, values for 60 of the compounds previously assessed are based on additional absorption spectra, and 42 compounds have REs which differ by >10% from our previous assessment. New RE calculations are presented for more than 400 compounds in addition to the previously assessed compounds, and GWP calculations are presented for a total of around 250 compounds. Present-day radiative forcing due to halocarbons and other weak absorbers is 0.38 [0.33-0.43] W m-2, compared to 0.36 [0.32-0.40] W m-2 in IPCC AR5 (Myhre et al., 2013, https://doi.org/10.1017/CBO9781107415324.018), which is about 18% of the current CO2 forcing.
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Affiliation(s)
- Ø Hodnebrog
- Center for International Climate Research (CICERO) Oslo Norway
| | - B Aamaas
- Center for International Climate Research (CICERO) Oslo Norway
| | - J S Fuglestvedt
- Center for International Climate Research (CICERO) Oslo Norway
| | - G Marston
- Vice-Chancellor's Office Northumbria University Newcastle UK
| | - G Myhre
- Center for International Climate Research (CICERO) Oslo Norway
| | - C J Nielsen
- Department of Chemistry University of Oslo Oslo Norway
| | - M Sandstad
- Center for International Climate Research (CICERO) Oslo Norway
| | - K P Shine
- Department of Meteorology University of Reading Reading UK
| | - T J Wallington
- Research and Advanced Eng. Ford Motor Company Dearborn MI USA
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Abstract
Methane emissions contribute to global warming, damage public health and reduce the yield of agricultural and forest ecosystems. Quantifying these damages to the planetary commons by calculating the social cost of methane (SCM) facilitates more comprehensive cost-benefit analyses of methane emissions control measures and is the first step to potentially incorporating them into the marketplace. Use of a broad measure of social welfare is also an attractive alternative or supplement to emission metrics focused on a temperature target in a given year as it incentivizes action to provide benefits over a broader range of impacts and timescales. Calculating the SCM using consistent temporal treatment of physical and economic processes and incorporating climate- and air quality-related impacts, we find large SCM values, e.g. ∼$2400 per ton and ∼$3600 per ton with 5% and 3% discount rates respectively. These values are ∼100 and 50 times greater than corresponding social costs for carbon dioxide. Our results suggest that ∼110 of 140 Mt of identified methane abatement via scaling up existing technology and policy options provide societal benefits that outweigh implementation costs. Within the energy sector, renewables compare far better against use of natural gas in electricity generation when incorporating these social costs for methane. In the agricultural sector, changes in livestock management practices, promoting healthy diets including reduced beef and dairy consumption, and reductions in food waste have been promoted as ways to mitigate emissions, and these are shown here to indeed have the potential to provide large societal benefits (∼$50-150 billion per year). Examining recent trends in methane and carbon dioxide, we find that increases in methane emissions may have offset much of the societal benefits from a slowdown in the growth rate of carbon dioxide emissions. The results indicate that efforts to reduce methane emissions via policies spanning a wide range of technical, regulatory and behavioural options provide benefits at little or negative net cost. Recognition of the full SCM, which has typically been undervalued, may help catalyze actions to reduce emissions and thereby provide a broad set of societal benefits.
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Affiliation(s)
- D T Shindell
- Nicholas School of the Environment, Duke University, Durham, NC 27708 USA.
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Samset BH, Sand M, Smith CJ, Bauer SE, Forster PM, Fuglestvedt JS, Osprey S, Schleussner CF. Climate Impacts From a Removal of Anthropogenic Aerosol Emissions. Geophys Res Lett 2018; 45:1020-1029. [PMID: 32801404 PMCID: PMC7427631 DOI: 10.1002/2017gl076079] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Limiting global warming to 1.5 or 2.0°C requires strong mitigation of anthropogenic greenhouse gas (GHG) emissions. Concurrently, emissions of anthropogenic aerosols will decline, due to coemission with GHG, and measures to improve air quality. However, the combined climate effect of GHG and aerosol emissions over the industrial era is poorly constrained. Here we show the climate impacts from removing present-day anthropogenic aerosol emissions and compare them to the impacts from moderate GHG-dominated global warming. Removing aerosols induces a global mean surface heating of 0.5-1.1°C, and precipitation increase of 2.0-4.6%. Extreme weather indices also increase. We find a higher sensitivity of extreme events to aerosol reductions, per degree of surface warming, in particular over the major aerosol emission regions. Under near-term warming, we find that regional climate change will depend strongly on the balance between aerosol and GHG forcing.
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Affiliation(s)
- B. H. Samset
- CICERO Center for International Climate and Environmental Research, Oslo, Norway
| | - M. Sand
- CICERO Center for International Climate and Environmental Research, Oslo, Norway
| | - C. J. Smith
- School of Earth and Environment, University of Leeds, Leeds, UK
| | - S. E. Bauer
- NASA Goddard Institute for Space Studies and Columbia Earth Institute, New York, NY, USA
| | - P. M. Forster
- School of Earth and Environment, University of Leeds, Leeds, UK
| | - J. S. Fuglestvedt
- CICERO Center for International Climate and Environmental Research, Oslo, Norway
| | - S. Osprey
- National Centre for Atmospheric Science and Department of Physics, University of Oxford, Oxford, UK
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Abstract
Abstract. In the context of climate change, emissions of different species (e.g., carbon dioxide and methane) are not directly comparable since they have different radiative efficiencies and lifetimes. Since comparisons via detailed climate models are computationally expensive and complex, emission metrics were developed to allow a simple and straightforward comparison of the estimated climate impacts of emissions of different species. Emission metrics are not unique and variety of different emission metrics has been proposed, with key choices being the climate impacts and time horizon to use for comparisons. In this paper, we present analytical expressions and describe how to calculate common emission metrics for different species. We include the climate metrics radiative forcing, integrated radiative forcing, temperature change and integrated temperature change in both absolute form and normalised to a reference gas. We consider pulse emissions, sustained emissions and emission scenarios. The species are separated into three types: CO2 which has a complex decay over time, species with a simple exponential decay, and ozone precursors (NOx, CO, VOC) which indirectly effect climate via various chemical interactions. We also discuss deriving Impulse Response Functions, radiative efficiency, regional dependencies, consistency within and between metrics and uncertainties. We perform various applications to highlight key applications of emission metrics, which show that emissions of CO2 are important regardless of what metric and time horizon is used, but that the importance of short lived climate forcers varies greatly depending on the metric choices made. Further, the ranking of countries by emissions changes very little with different metrics despite large differences in metric values, except for the shortest time horizons (GWP20).
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Shine KP, Berntsen TK, Fuglestvedt JS, Sausen R. Scientific issues in the design of metrics for inclusion of oxides of nitrogen in global climate agreements. Proc Natl Acad Sci U S A 2005; 102:15768-73. [PMID: 16243971 PMCID: PMC1276078 DOI: 10.1073/pnas.0506865102] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Kyoto Protocol seeks to limit emissions of various greenhouse gases but excludes short-lived species and their precursors even though they cause a significant climate forcing. We explore the difficulties that are faced when designing metrics to compare the climate impact of emissions of oxides of nitrogen (NO(x)) with other emissions. There are two dimensions to this difficulty. The first concerns the definition of a metric that satisfactorily accounts for its climate impact. NO(x) emissions increase tropospheric ozone, but this increase and the resulting climate forcing depend strongly on the location of the emissions, with low-latitude emissions having a larger impact. NO(x) emissions also decrease methane concentrations, causing a global-mean radiative forcing similar in size but opposite in sign to the ozone forcing. The second dimension of difficulty concerns the intermodel differences in the values of computed metrics. We explore the use of indicators that could lead to metrics that, instead of using global-mean inputs, are computed locally and then averaged globally. These local metrics may depend less on cancellation in the global mean; the possibilities presented here seem more robust to model uncertainty, although their applicability depends on the poorly known relationship between local climate change and its societal/ecological impact. If it becomes a political imperative to include NO(x) emissions in future climate agreements, policy makers will be faced with difficult choices in selecting an appropriate metric.
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Affiliation(s)
- K P Shine
- Department of Meteorology, University of Reading, Earley Gate, Reading RG6 6BB, United Kingdom.
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Berntsen TK, Isaksen ISA, Myhre G, Fuglestvedt JS, Stordal F, Larsen TA, Freckleton RS, Shine KP. Effects of anthropogenic emissions on tropospheric ozone and its radiative forcing. ACTA ACUST UNITED AC 1997. [DOI: 10.1029/97jd02226] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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