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Thompson V, Mitchell D, Hegerl GC, Collins M, Leach NJ, Slingo JM. The most at-risk regions in the world for high-impact heatwaves. Nat Commun 2023; 14:2152. [PMID: 37185667 PMCID: PMC10130074 DOI: 10.1038/s41467-023-37554-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 03/22/2023] [Indexed: 05/17/2023] Open
Abstract
Heatwaves are becoming more frequent under climate change and can lead to thousands of excess deaths. Adaptation to extreme weather events often occurs in response to an event, with communities learning fast following unexpectedly impactful events. Using extreme value statistics, here we show where regional temperature records are statistically likely to be exceeded, and therefore communities might be more at-risk. In 31% of regions examined, the observed daily maximum temperature record is exceptional. Climate models suggest that similar behaviour can occur in any region. In some regions, such as Afghanistan and parts of Central America, this is a particular problem - not only have they the potential for far more extreme heatwaves than experienced, but their population is growing and increasingly exposed because of limited healthcare and energy resources. We urge policy makers in vulnerable regions to consider if heat action plans are sufficient for what might come.
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Affiliation(s)
- Vikki Thompson
- School of Geographical Sciences, University of Bristol, Bristol, UK.
| | - Dann Mitchell
- School of Geographical Sciences, University of Bristol, Bristol, UK
| | | | - Matthew Collins
- Department of Mathematics and Statistics, University of Exeter, Exeter, UK
| | - Nicholas J Leach
- Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, UK
- Climate X, 1st Floor, 21 Great Winchester Street, London, UK
| | - Julia M Slingo
- School of Geographical Sciences, University of Bristol, Bristol, UK
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2
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Olonscheck D, Schurer AP, Lücke L, Hegerl GC. Large-scale emergence of regional changes in year-to-year temperature variability by the end of the 21 st century. Nat Commun 2021; 12:7237. [PMID: 34903720 PMCID: PMC8668997 DOI: 10.1038/s41467-021-27515-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Accepted: 11/19/2021] [Indexed: 11/09/2022] Open
Abstract
Global warming is expected to not only impact mean temperatures but also temperature variability, substantially altering climate extremes. Here we show that human-caused changes in internal year-to-year temperature variability are expected to emerge from the unforced range by the end of the 21st century across climate model initial-condition large ensembles forced with a strong global warming scenario. Different simulated changes in globally averaged regional temperature variability between models can be explained by a trade-off between strong increases in variability on tropical land and substantial decreases in high latitudes, both shown by most models. This latitudinal pattern of temperature variability change is consistent with loss of sea ice in high latitudes and changes in vegetation cover in the tropics. Instrumental records are broadly in line with this emerging pattern, but have data gaps in key regions. Paleoclimate proxy reconstructions support the simulated magnitude and distribution of temperature variability. Our findings strengthen the need for urgent mitigation to avoid unprecedented changes in temperature variability.
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Affiliation(s)
- Dirk Olonscheck
- School of GeoSciences, University of Edinburgh, Edinburgh, EH9 3JW, UK. .,Max Planck Institute for Meteorology, 20146, Hamburg, Germany.
| | - Andrew P. Schurer
- grid.4305.20000 0004 1936 7988School of GeoSciences, University of Edinburgh, Edinburgh, EH9 3JW UK
| | - Lucie Lücke
- grid.4305.20000 0004 1936 7988School of GeoSciences, University of Edinburgh, Edinburgh, EH9 3JW UK
| | - Gabriele C. Hegerl
- grid.4305.20000 0004 1936 7988School of GeoSciences, University of Edinburgh, Edinburgh, EH9 3JW UK
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3
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Fowler HJ, Ali H, Allan RP, Ban N, Barbero R, Berg P, Blenkinsop S, Cabi NS, Chan S, Dale M, Dunn RJH, Ekström M, Evans JP, Fosser G, Golding B, Guerreiro SB, Hegerl GC, Kahraman A, Kendon EJ, Lenderink G, Lewis E, Li X, O'Gorman PA, Orr HG, Peat KL, Prein AF, Pritchard D, Schär C, Sharma A, Stott PA, Villalobos-Herrera R, Villarini G, Wasko C, Wehner MF, Westra S, Whitford A. Towards advancing scientific knowledge of climate change impacts on short-duration rainfall extremes. Philos Trans A Math Phys Eng Sci 2021; 379:20190542. [PMID: 33641464 DOI: 10.1098/rsta.2019.0542] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 01/14/2021] [Indexed: 06/12/2023]
Abstract
A large number of recent studies have aimed at understanding short-duration rainfall extremes, due to their impacts on flash floods, landslides and debris flows and potential for these to worsen with global warming. This has been led in a concerted international effort by the INTENSE Crosscutting Project of the GEWEX (Global Energy and Water Exchanges) Hydroclimatology Panel. Here, we summarize the main findings so far and suggest future directions for research, including: the benefits of convection-permitting climate modelling; towards understanding mechanisms of change; the usefulness of temperature-scaling relations; towards detecting and attributing extreme rainfall change; and the need for international coordination and collaboration. Evidence suggests that the intensity of long-duration (1 day+) heavy precipitation increases with climate warming close to the Clausius-Clapeyron (CC) rate (6-7% K-1), although large-scale circulation changes affect this response regionally. However, rare events can scale at higher rates, and localized heavy short-duration (hourly and sub-hourly) intensities can respond more strongly (e.g. 2 × CC instead of CC). Day-to-day scaling of short-duration intensities supports a higher scaling, with mechanisms proposed for this related to local-scale dynamics of convective storms, but its relevance to climate change is not clear. Uncertainty in changes to precipitation extremes remains and is influenced by many factors, including large-scale circulation, convective storm dynamics andstratification. Despite this, recent research has increased confidence in both the detectability and understanding of changes in various aspects of intense short-duration rainfall. To make further progress, the international coordination of datasets, model experiments and evaluations will be required, with consistent and standardized comparison methods and metrics, and recommendations are made for these frameworks. This article is part of a discussion meeting issue 'Intensification of short-duration rainfall extremes and implications for flash flood risks'.
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Affiliation(s)
- Hayley J Fowler
- School of Engineering, Newcastle University, Newcastle upon Tyne, UK
| | - Haider Ali
- School of Engineering, Newcastle University, Newcastle upon Tyne, UK
| | - Richard P Allan
- Department of Meteorology and National Centre for Earth Observation, University of Reading, Reading, UK
| | - Nikolina Ban
- Department of Atmospheric and Cryospheric Sciences, University of Innsbruck, Innsbruck, Austria
| | - Renaud Barbero
- National Research Institute for Agriculture, Food and Environment, RECOVER, Aix-en-Provence, France
| | - Peter Berg
- Hydrology Research Unit, Swedish Meteorological and Hydrological Institute, Norrköping, Sweden
| | | | - Nalan Senol Cabi
- Willis Research Network (WRN), Willis Towers Watson (WTW), London, UK
| | - Steven Chan
- School of Engineering, Newcastle University, Newcastle upon Tyne, UK
- Met Office Hadley Centre, Exeter, UK
| | | | | | - Marie Ekström
- School of Earth and Ocean Sciences, Cardiff University, UK
| | - Jason P Evans
- Climate Change Research Centre and the ARC Centre of Excellence for Climate Extremes, University of New South Wales, Sydney, New South Wales, Australia
| | | | | | - Selma B Guerreiro
- School of Engineering, Newcastle University, Newcastle upon Tyne, UK
| | | | - Abdullah Kahraman
- School of Engineering, Newcastle University, Newcastle upon Tyne, UK
- Met Office Hadley Centre, Exeter, UK
| | | | - Geert Lenderink
- Royal Netherlands Meteorological Institute, De Bilt, the Netherlands
| | - Elizabeth Lewis
- School of Engineering, Newcastle University, Newcastle upon Tyne, UK
| | - Xiaofeng Li
- School of Engineering, Newcastle University, Newcastle upon Tyne, UK
| | - Paul A O'Gorman
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, USA
| | | | - Katy L Peat
- School of Engineering, Newcastle University, Newcastle upon Tyne, UK
- Environment Agency, Horizon House, Bristol, UK
| | | | - David Pritchard
- School of Engineering, Newcastle University, Newcastle upon Tyne, UK
| | - Christoph Schär
- Institute for Atmospheric and Climate Science, ETH Zürich, Zürich, Switzerland
| | - Ashish Sharma
- School of Civil and Environmental Engineering, University of New South Wales, Sydney, New South Wales, Australia
| | - Peter A Stott
- Met Office Hadley Centre, Exeter, UK
- College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, UK
| | - Roberto Villalobos-Herrera
- School of Engineering, Newcastle University, Newcastle upon Tyne, UK
- School of Civil Engineering, Universidad de Costa Rica, Ciudad Universitaria Rodrigo Facio, San José, Costa Rica
| | - Gabriele Villarini
- IIHR-Hydroscience & Engineering, The University of Iowa, Iowa City, IA, USA
| | - Conrad Wasko
- Department of Infrastructure Engineering, The University of Melbourne, Victoria, Australia
| | - Michael F Wehner
- Computational Research Division, Lawrence Berkeley National Laboratory, San Francisco, USA
| | - Seth Westra
- School of Civil, Environmental and Mining Engineering, University of Adelaide, Adelaide, South Australia, Australia
| | - Anna Whitford
- School of Engineering, Newcastle University, Newcastle upon Tyne, UK
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4
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Hegerl GC, Brönnimann S, Schurer A, Cowan T. The early 20th century warming: Anomalies, causes, and consequences. Wiley Interdiscip Rev Clim Change 2018; 9:e522. [PMID: 30008810 PMCID: PMC6033150 DOI: 10.1002/wcc.522] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2017] [Revised: 03/19/2018] [Accepted: 03/20/2018] [Indexed: 05/22/2023]
Abstract
The most pronounced warming in the historical global climate record prior to the recent warming occurred over the first half of the 20th century and is known as the Early Twentieth Century Warming (ETCW). Understanding this period and the subsequent slowdown of warming is key to disentangling the relationship between decadal variability and the response to human influences in the present and future climate. This review discusses the observed changes during the ETCW and hypotheses for the underlying causes and mechanisms. Attribution studies estimate that about a half (40-54%; p > .8) of the global warming from 1901 to 1950 was forced by a combination of increasing greenhouse gases and natural forcing, offset to some extent by aerosols. Natural variability also made a large contribution, particularly to regional anomalies like the Arctic warming in the 1920s and 1930s. The ETCW period also encompassed exceptional events, several of which are touched upon: Indian monsoon failures during the turn of the century, the "Dust Bowl" droughts and extreme heat waves in North America in the 1930s, the World War II period drought in Australia between 1937 and 1945; and the European droughts and heat waves of the late 1940s and early 1950s. Understanding the mechanisms involved in these events, and their links to large scale forcing is an important test for our understanding of modern climate change and for predicting impacts of future change. This article is categorized under:Paleoclimates and Current Trends > Modern Climate Change.
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Affiliation(s)
| | - Stefan Brönnimann
- Oeschger Centre for Climate Change ResearchUniversity of BernBernSwitzerland
- Institute of GeographyUniversity of BernBernSwitzerland
| | | | - Tim Cowan
- School of GeoSciencesUniversity of EdinburghEdinburghUK
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5
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Schurer AP, Mann ME, Hawkins E, Tett SFB, Hegerl GC. Importance of the Pre-Industrial Baseline in Determining the Likelihood of Exceeding the Paris Limits. Nat Clim Chang 2017; 7:563-567. [PMID: 28785317 PMCID: PMC5544117 DOI: 10.1038/nclimate3345] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 06/14/2017] [Indexed: 05/22/2023]
Abstract
During the Paris Conference in 2015, nations of the world strengthened the United Nations Framework Convention on Climate Change by agreeing to holding "the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C"1. However, "pre-industrial" was not defined. Here we investigate the implications of different choices of the pre-industrial baseline on the likelihood of exceeding these two temperature thresholds. We find that for the strongest mitigation scenario RCP2.6 and a medium scenario RCP4.5 the probability of exceeding the thresholds and timing of exceedance is highly dependent on the pre-industrial baseline, for example the probability of crossing 1.5°C by the end of the century under RCP2.6, varies from 61% to 88% depending on how the baseline is defined. In contrast, in the scenario with no mitigation, RCP8.5, both thresholds will almost certainly be exceeded by the middle of the century with the definition of the pre-industrial baseline of less importance. Allowable carbon emissions for threshold stabilisation are similarly highly dependent on the pre-industrial baseline. For stabilisation at 2°C, allowable emissions decrease by as much as 40% when earlier than 19th century climates are considered as a baseline.
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Affiliation(s)
- Andrew P Schurer
- School of GeoSciences, University of Edinburgh, Crew Building, Alexander Crum Brown Road, Edinburgh, EH9 3FF, United Kingdom
| | - Michael E Mann
- Dept. of Meteorology and Atmospheric Science & Earth and Environmental Systems Institute, Pennsylvania State University, State College, PA
| | - Ed Hawkins
- NCAS-Climate, Dept. of Meteorology, University of Reading, Reading, RG6 6BB, United Kingdom
| | - Simon F B Tett
- School of GeoSciences, University of Edinburgh, Crew Building, Alexander Crum Brown Road, Edinburgh, EH9 3FF, United Kingdom
| | - Gabriele C Hegerl
- School of GeoSciences, University of Edinburgh, Crew Building, Alexander Crum Brown Road, Edinburgh, EH9 3FF, United Kingdom
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6
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Iles CE, Hegerl GC. Systematic change in global patterns of streamflow following volcanic eruptions. Nat Geosci 2015; 8:838-842. [PMID: 27279897 PMCID: PMC4894545 DOI: 10.1038/ngeo2545] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Accepted: 08/20/2015] [Indexed: 05/24/2023]
Abstract
Following large explosive volcanic eruptions precipitation decreases over much of the globe1-6, particularly in climatologically wet regions4,5. Stratospheric volcanic aerosols reflect sunlight, which reduces evaporation, whilst surface cooling stabilises the atmosphere and reduces its water-holding capacity7. Circulation changes modulate this global precipitation reduction on regional scales1,8-10. Despite the importance of rivers to people, it has been unclear whether volcanism causes detectable changes in streamflow given large natural variability. Here we analyse observational records of streamflow volume for fifty large rivers from around the world which cover between two and 6 major volcanic eruptions in the 20th and late 19th century. We find statistically significant reductions in flow following eruptions for the Amazon, Congo, Nile, Orange, Ob, Yenisey and Kolyma amongst others. When data from neighbouring rivers are combined - based on the areas where climate models simulate either an increase or a decrease in precipitation following eruptions - a significant (p<0.1) decrease in streamflow following eruptions is detected in northern South American, central African and high-latitude Asian rivers, and on average across wet tropical and subtropical regions. We also detect a significant increase in southern South American and SW North American rivers. This suggests that future volcanic eruptions could substantially affect global water availability.
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Affiliation(s)
- Carley E. Iles
- School of Geosciences, University of Edinburgh, James Hutton Road, Edinburgh EH9 3FE, UK
| | - Gabriele C. Hegerl
- School of Geosciences, University of Edinburgh, James Hutton Road, Edinburgh EH9 3FE, UK
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7
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Min SK, Zhang X, Zwiers FW, Hegerl GC. Human contribution to more-intense precipitation extremes. Nature 2011; 470:378-81. [PMID: 21331039 DOI: 10.1038/nature09763] [Citation(s) in RCA: 315] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Accepted: 12/17/2010] [Indexed: 11/09/2022]
Abstract
Extremes of weather and climate can have devastating effects on human society and the environment. Understanding past changes in the characteristics of such events, including recent increases in the intensity of heavy precipitation events over a large part of the Northern Hemisphere land area, is critical for reliable projections of future changes. Given that atmospheric water-holding capacity is expected to increase roughly exponentially with temperature--and that atmospheric water content is increasing in accord with this theoretical expectation--it has been suggested that human-influenced global warming may be partly responsible for increases in heavy precipitation. Because of the limited availability of daily observations, however, most previous studies have examined only the potential detectability of changes in extreme precipitation through model-model comparisons. Here we show that human-induced increases in greenhouse gases have contributed to the observed intensification of heavy precipitation events found over approximately two-thirds of data-covered parts of Northern Hemisphere land areas. These results are based on a comparison of observed and multi-model simulated changes in extreme precipitation over the latter half of the twentieth century analysed with an optimal fingerprinting technique. Changes in extreme precipitation projected by models, and thus the impacts of future changes in extreme precipitation, may be underestimated because models seem to underestimate the observed increase in heavy precipitation with warming.
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Affiliation(s)
- Seung-Ki Min
- Climate Research Division, Environment Canada, Toronto, Ontario M3H5T4, Canada.
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8
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Zhang X, Zwiers FW, Hegerl GC, Lambert FH, Gillett NP, Solomon S, Stott PA, Nozawa T. Detection of human influence on twentieth-century precipitation trends. Nature 2007; 448:461-5. [PMID: 17646832 DOI: 10.1038/nature06025] [Citation(s) in RCA: 159] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2007] [Accepted: 06/14/2007] [Indexed: 11/09/2022]
Abstract
Human influence on climate has been detected in surface air temperature, sea level pressure, free atmospheric temperature, tropopause height and ocean heat content. Human-induced changes have not, however, previously been detected in precipitation at the global scale, partly because changes in precipitation in different regions cancel each other out and thereby reduce the strength of the global average signal. Models suggest that anthropogenic forcing should have caused a small increase in global mean precipitation and a latitudinal redistribution of precipitation, increasing precipitation at high latitudes, decreasing precipitation at sub-tropical latitudes, and possibly changing the distribution of precipitation within the tropics by shifting the position of the Intertropical Convergence Zone. Here we compare observed changes in land precipitation during the twentieth century averaged over latitudinal bands with changes simulated by fourteen climate models. We show that anthropogenic forcing has had a detectable influence on observed changes in average precipitation within latitudinal bands, and that these changes cannot be explained by internal climate variability or natural forcing. We estimate that anthropogenic forcing contributed significantly to observed increases in precipitation in the Northern Hemisphere mid-latitudes, drying in the Northern Hemisphere subtropics and tropics, and moistening in the Southern Hemisphere subtropics and deep tropics. The observed changes, which are larger than estimated from model simulations, may have already had significant effects on ecosystems, agriculture and human health in regions that are sensitive to changes in precipitation, such as the Sahel.
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Affiliation(s)
- Xuebin Zhang
- Climate Research Division, Environment Canada, Toronto, Ontario M3H 5T4, Canada
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Hegerl GC, Crowley TJ, Hyde WT, Frame DJ. Climate sensitivity constrained by temperature reconstructions over the past seven centuries. Nature 2006; 440:1029-32. [PMID: 16625192 DOI: 10.1038/nature04679] [Citation(s) in RCA: 301] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2005] [Accepted: 02/28/2006] [Indexed: 11/09/2022]
Abstract
The magnitude and impact of future global warming depends on the sensitivity of the climate system to changes in greenhouse gas concentrations. The commonly accepted range for the equilibrium global mean temperature change in response to a doubling of the atmospheric carbon dioxide concentration, termed climate sensitivity, is 1.5-4.5 K (ref. 2). A number of observational studies, however, find a substantial probability of significantly higher sensitivities, yielding upper limits on climate sensitivity of 7.7 K to above 9 K (refs 3-8). Here we demonstrate that such observational estimates of climate sensitivity can be tightened if reconstructions of Northern Hemisphere temperature over the past several centuries are considered. We use large-ensemble energy balance modelling and simulate the temperature response to past solar, volcanic and greenhouse gas forcing to determine which climate sensitivities yield simulations that are in agreement with proxy reconstructions. After accounting for the uncertainty in reconstructions and estimates of past external forcing, we find an independent estimate of climate sensitivity that is very similar to those from instrumental data. If the latter are combined with the result from all proxy reconstructions, then the 5-95 per cent range shrinks to 1.5-6.2 K, thus substantially reducing the probability of very high climate sensitivity.
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Affiliation(s)
- Gabriele C Hegerl
- Division of Earth and Ocean Sciences, Nicholas School of the Environment and Earth Sciences, Duke University, Durham, North Carolina 27708, USA.
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10
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Affiliation(s)
- Gabriele C Hegerl
- Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708, USA.
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11
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Abstract
Simulations using global coupled climate models predict a climate change due to the increasing concentration of greenhouse gases and aerosols in the atmosphere. Both are associated with the burning of fossil fuels. There has been considerable debate if this postulated human influence is already evident. This paper gives an overview on some recent material on this question. One particular study using optimal fingerprints (Hegerl et al., 1996) is explained in more detail. In this study, an optimal fingerprint analysis is applied to temperature trend patterns over several decades. The results show the probability being less than 5% that the most recently observed 30 year trend is due to naturally occurring climate fluctuations. This result suggests that the present warming is caused by some external influence on climate, e.g. by the increasing concentrations of greenhouse gases and aerosols. More work is needed to address the uncertainties in the magnitude of naturally occurring climate fluctuations. Also, other external influences on climate need to be investigated to uniquely attribute the present climate change to the human influence.
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Affiliation(s)
- G C Hegerl
- Max-Planck-Institut für Meteorologie, Bundesstraße 55, D-20146, Hamburg, Germany
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