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How Much Human-Caused Global Warming Should We Expect with Business-As-Usual (BAU) Climate Policies? A Semi-Empirical Assessment. ENERGIES 2020. [DOI: 10.3390/en13061365] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In order to assess the merits of national climate change mitigation policies, it is important to have a reasonable benchmark for how much human-caused global warming would occur over the coming century with “Business-As-Usual” (BAU) conditions. However, currently, policymakers are limited to making assessments by comparing the Global Climate Model (GCM) projections of future climate change under various different “scenarios”, none of which are explicitly defined as BAU. Moreover, all of these estimates are ab initio computer model projections, and policymakers do not currently have equivalent empirically derived estimates for comparison. Therefore, estimates of the total future human-caused global warming from the three main greenhouse gases of concern (CO2, CH4, and N2O) up to 2100 are here derived for BAU conditions. A semi-empirical approach is used that allows direct comparisons between GCM-based estimates and empirically derived estimates. If the climate sensitivity to greenhouse gases implies a Transient Climate Response (TCR) of ≥ 2.5 °C or an Equilibrium Climate Sensitivity (ECS) of ≥ 5.0 °C then the 2015 Paris Agreement’s target of keeping human-caused global warming below 2.0 °C will have been broken by the middle of the century under BAU. However, for a TCR < 1.5 °C or ECS < 2.0 °C, the target would not be broken under BAU until the 22nd century or later. Therefore, the current Intergovernmental Panel on Climate Change (IPCC) “likely” range estimates for TCR of 1.0 to 2.5 °C and ECS of 1.5 to 4.5 °C have not yet established if human-caused global warming is a 21st century problem.
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No evidence for globally coherent warm and cold periods over the preindustrial Common Era. Nature 2019; 571:550-554. [PMID: 31341300 DOI: 10.1038/s41586-019-1401-2] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2018] [Accepted: 05/28/2019] [Indexed: 11/09/2022]
Abstract
Earth's climate history is often understood by breaking it down into constituent climatic epochs1. Over the Common Era (the past 2,000 years) these epochs, such as the Little Ice Age2-4, have been characterized as having occurred at the same time across extensive spatial scales5. Although the rapid global warming seen in observations over the past 150 years does show nearly global coherence6, the spatiotemporal coherence of climate epochs earlier in the Common Era has yet to be robustly tested. Here we use global palaeoclimate reconstructions for the past 2,000 years, and find no evidence for preindustrial globally coherent cold and warm epochs. In particular, we find that the coldest epoch of the last millennium-the putative Little Ice Age-is most likely to have experienced the coldest temperatures during the fifteenth century in the central and eastern Pacific Ocean, during the seventeenth century in northwestern Europe and southeastern North America, and during the mid-nineteenth century over most of the remaining regions. Furthermore, the spatial coherence that does exist over the preindustrial Common Era is consistent with the spatial coherence of stochastic climatic variability. This lack of spatiotemporal coherence indicates that preindustrial forcing was not sufficient to produce globally synchronous extreme temperatures at multidecadal and centennial timescales. By contrast, we find that the warmest period of the past two millennia occurred during the twentieth century for more than 98 per cent of the globe. This provides strong evidence that anthropogenic global warming is not only unparalleled in terms of absolute temperatures5, but also unprecedented in spatial consistency within the context of the past 2,000 years.
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Affiliation(s)
- Jon C. Lovett
- The School of Geography; University of Leeds; Leeds LS2 9JT U.K
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Marcott SA, Shakun JD, Clark PU, Mix AC. A Reconstruction of Regional and Global Temperature for the Past 11,300 Years. Science 2013; 339:1198-201. [PMID: 23471405 DOI: 10.1126/science.1228026] [Citation(s) in RCA: 224] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
MESH Headings
- Global Warming/history
- Global Warming/statistics & numerical data
- History, 15th Century
- History, 16th Century
- History, 17th Century
- History, 18th Century
- History, 19th Century
- History, 20th Century
- History, 21st Century
- History, Ancient
- History, Medieval
- Models, Theoretical
- Temperature
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Affiliation(s)
- Shaun A Marcott
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA.
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McShane BB, Wyner AJ. A statistical analysis of multiple temperature proxies: Are reconstructions of surface temperatures over the last 1000 years reliable? Ann Appl Stat 2011. [DOI: 10.1214/10-aoas398] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Schneider DP, Noone DC. Spatial covariance of water isotope records in a global network of ice cores spanning twentieth-century climate change. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2007jd008652] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Mann ME, Rutherford S, Wahl E, Ammann C. Robustness of proxy-based climate field reconstruction methods. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2006jd008272] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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von Storch H, Zorita E, Jones JM, Gonzalez-Rouco F, Tett SFB. Response to Comment on "Reconstructing Past Climate from Noisy Data". Science 2006. [DOI: 10.1126/science.1121571] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- Hans von Storch
- Institute for Coastal Research, GKSS Research Centre, Geesthacht, Germany
- Department of Astrophysics and Atmospheric Physics, Universidad Complutense, Madrid 28040, Spain
- UK Meteorological Office, Hadley Centre (Reading Unit), Meteorology Building, University of Reading, Reading, RG6 6BB, UK
| | - Eduardo Zorita
- Institute for Coastal Research, GKSS Research Centre, Geesthacht, Germany
- Department of Astrophysics and Atmospheric Physics, Universidad Complutense, Madrid 28040, Spain
- UK Meteorological Office, Hadley Centre (Reading Unit), Meteorology Building, University of Reading, Reading, RG6 6BB, UK
| | - Julie M. Jones
- Institute for Coastal Research, GKSS Research Centre, Geesthacht, Germany
- Department of Astrophysics and Atmospheric Physics, Universidad Complutense, Madrid 28040, Spain
- UK Meteorological Office, Hadley Centre (Reading Unit), Meteorology Building, University of Reading, Reading, RG6 6BB, UK
| | - Fidel Gonzalez-Rouco
- Institute for Coastal Research, GKSS Research Centre, Geesthacht, Germany
- Department of Astrophysics and Atmospheric Physics, Universidad Complutense, Madrid 28040, Spain
- UK Meteorological Office, Hadley Centre (Reading Unit), Meteorology Building, University of Reading, Reading, RG6 6BB, UK
| | - Simon F. B. Tett
- Institute for Coastal Research, GKSS Research Centre, Geesthacht, Germany
- Department of Astrophysics and Atmospheric Physics, Universidad Complutense, Madrid 28040, Spain
- UK Meteorological Office, Hadley Centre (Reading Unit), Meteorology Building, University of Reading, Reading, RG6 6BB, UK
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Mann ME, Hughes MK. A Not-So-Abrupt Departure. Science 2006; 312:528-9. [PMID: 16645077 DOI: 10.1126/science.312.5773.528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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