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Detection of human and natural influences on the climate system: regional insights from the past Millennium

Applicant Neukom Raphael
Number 154802
Funding scheme Ambizione
Research institution Oeschger-Zentrum für Klimaforschung Universität Bern
Institution of higher education University of Berne - BE
Main discipline Climatology. Atmospherical Chemistry, Aeronomy
Start/End 01.05.2015 - 28.02.2019
Approved amount 563'036.00
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All Disciplines (4)

Discipline
Climatology. Atmospherical Chemistry, Aeronomy
Hydrology, Limnology, Glaciology
Oceanography
Other disciplines of Environmental Sciences

Keywords (7)

Data-model comparison; Southern Hemisphere; Climate reconstruction; Paleoclimatology; Detection and attribution; Climate variability; Climate change

Lay Summary (German)

Lead
Verlässliche Voraussagen des zukünftigen Klimas benötigen ein gutes Verständnis der Prozesse im globalen Klimasystem. Zum Beispiel ist es wichtig zu verstehen, wie gross die relativen Einflüsse von menschlichen Aktivitäten (Treibhausgas-Emissionen, Aerosole, Landnutzung, etc.) und natürlichen Einflüssen sind. Dabei unterscheidet man zwischen dem sogenannten external forcing (z.B. menschliche Einflüsse, Schwankungen in der Sonneneinstrahlung oder Vulkanausbrüche) und dem internal forcing (natürliche chaotische Schwankungen innerhalb des Klimasystems). Die Messreihen dieser Klima- und Forcing-Parameter sind jedoch nur maximal 150 Jahre lang, Schwankungen im Multi-dekadischen und längeren Zeiträumen sind deshalb schwierig zu quantifizieren. Fast alle Studien, welche die Einflüsse von internal und external forcing quantifizieren beziehen sich ausserdem auf die Nordhemisphäre, während von der Südhemisphäre fast gar keine Daten dazu existieren.
Lay summary

Inhalt und Ziele

Hauptziel ist, den Einfluss von external und internal forcing auf Klimaschwankungen der letzten 1000 Jahre zu quantifizieren. Als Datengrundlage dafür werden sogenannte Klima-Proxies (z.B. Baumringe, Eisbohrkerne, Korallen, historische Dokumente etc.) und Klimamodelle verwendet. Der Fokus liegt dabei auf der Südhemisphäre, um Vergleiche zwischen den verschiedenen Kontinenten zu ermöglichen.

Wissenschaftlicher und gesellschaftlicher Kontext

Unsere Arbeit wird regionale Aussagen zur Stärke verschiedener Einflussfaktoren auf das Klima ermöglichen. Die Resultate werden deshalb helfen, Projektionen des zukünftigen Klimas zu verbessern. Das Projekt liefert damit entscheidende Datengrundlagen für politische Entscheide und gesellschaftliche Diskussionen im Zusammenhang mit dem Klimawandel.

Direct link to Lay Summary Last update: 06.05.2015

Responsible applicant and co-applicants

Employees

Publications

Publication
Teleconnections and relationship between the El Niño-Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) in reconstructions and models over the past millennium
Dätwyler Christoph, Grosjean Martin, Steiger Nathan J., Neukom Raphael (2020), Teleconnections and relationship between the El Niño-Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) in reconstructions and models over the past millennium, in Climate of the Past, 16(2), 743-756.
Unlocking Pre-1850 Instrumental Meteorological Records: A Global Inventory
Brönnimann Stefan, Allan Rob, Ashcroft Linden, Baer Saba, Barriendos Mariano, Brázdil Rudolf, Brugnara Yuri, Brunet Manola, Brunetti Michele, Chimani Barbara, Cornes Richard, Domínguez-Castro Fernando, Filipiak Janusz, Founda Dimitra, Herrera Ricardo García, Gergis Joelle, Grab Stefan, Hannak Lisa, Huhtamaa Heli, Jacobsen Kim S., Jones Phil, Jourdain Sylvie, Kiss Andrea, Lin Kuanhui Elaine, Neukom Raphael, et al. (2020), Unlocking Pre-1850 Instrumental Meteorological Records: A Global Inventory, in Bulletin of the American Meteorological Society, 100(12), ES389-ES413.
Consistent multidecadal variability in global temperature reconstructions and simulations over the Common Era
PAGES2k Consortium (2019), Consistent multidecadal variability in global temperature reconstructions and simulations over the Common Era, in Nature Geoscience, 12, 643-649.
Assessing the robustness of Antarctic temperature reconstructions over the past 2 millennia using pseudoproxy and data assimilation experiments
Klein François, Abram Nerilie J., Curran Mark A. J., Goosse Hugues, Goursaud Sentia, Masson-Delmotte Valérie, Moy Andrew, Neukom Raphael, Orsi Anaïs, Sjolte Jesper, Steiger Nathan, Stenni Barbara, Werner Martin (2019), Assessing the robustness of Antarctic temperature reconstructions over the past 2 millennia using pseudoproxy and data assimilation experiments, in Climate of the Past, 15(2), 661-684.
No evidence for globally coherent warm and cold periods over the pre-industrial Common Era
Neukom Raphael, Steiger Nathan, Gómez-Navarro Juan José, Wang Jianghao, Werner Johannes P. (2019), No evidence for globally coherent warm and cold periods over the pre-industrial Common Era, in Nature.
Spatial and temporal agreement in climate model simulations of the Interdecadal Pacific Oscillation
Henley Benjamin J, Meehl Gerald, Power Scott B, Folland Chris K, King Andrew D, Brown Jaclyn N, Karoly David J, Delage Francois, Gallant Ailie J E, Freund Mandy, Neukom Raphael (2017), Spatial and temporal agreement in climate model simulations of the Interdecadal Pacific Oscillation, in Environmental Research Letters, 12(4), 044011-044011.
The freezing level in the tropical Andes, Peru: An indicator for present and future glacier extentsThe Freezing Level in the Tropical Andes
Schauwecker Simone, Rohrer Mario, Huggel Christian, Endries Jason, Montoya Nilton, Neukom Raphael, Perry Baker, Salzmann Nadine, Schwarb Manfred, Suarez Wilson (2017), The freezing level in the tropical Andes, Peru: An indicator for present and future glacier extentsThe Freezing Level in the Tropical Andes, in Journal of Geophysical Research: Atmospheres.
The 1430s: a cold period of extraordinary internal climate variability during the early Spörer Minimum with social and economic impacts in north-western and central Europe
Camenisch Chantal, Keller Kathrin M., Salvisberg Melanie, Amann Benjamin, Bauch Martin, Blumer Sandro, Brázdil Rudolf, Brönnimann Stefan, Büntgen Ulf, Campbell Bruce M. S., Fernández-Donado Laura, Fleitmann Dominik, Glaser Rüdiger, González-Rouco Fidel, Grosjean Martin, Hoffmann Richard C., Huhtamaa Heli, Joos Fortunat, Kiss Andrea, Kotyza Oldřich, Lehner Flavio, Luterbacher Jürg, Maughan Nicolas, Neukom Raphael, et al. (2016), The 1430s: a cold period of extraordinary internal climate variability during the early Spörer Minimum with social and economic impacts in north-western and central Europe, in Climate of the Past, 12(11), 2107-2126.
Science in the Context of Climate Change Adaptation: Case Studies from the Peruvian Andes
Orlowsky Boris, Andres Norina, Salzmann Nadine, Huggel Christian, Jurt Christine, Vicuña Luis, Rohrer Mario, Calanca Pierluigi, Neukom Raphael, Drenkhan Fabian (2016), Science in the Context of Climate Change Adaptation: Case Studies from the Peruvian Andes, in Salzmann Nadine (ed.), Springer International Publishing, Cham, 41-58.
Early onset of industrial-era warming across the oceans and continents
Abram Nerilie J., McGregor Helen V., Tierney Jessica E., Evans Michael N., McKay Nicholas P., Kaufman Darrell S., Thirumalai Kaustubh, Martrat Belen, Goosse Hugues, Phipps Steven J., Steig Eric J., Kilbourne K. Halimeda, Saenger Casey P., Zinke Jens, Leduc Guillaume, Addison Jason A., Mortyn P. Graham, Seidenkrantz Marit-Solveig, Sicre Marie-Alexandrine, Selvaraj Kandasamy, Filipsson Helena L., Neukom Raphael, Gergis Joelle, Curran Mark A. J., et al. (2016), Early onset of industrial-era warming across the oceans and continents, in Nature, 536(7617), 411-418.
Seasonal rainfall variability in southeast Africa during the nineteenth century reconstructed from documentary sources
Nash David J., Pribyl Kathleen, Klein J{ø}rgen, Neukom Raphael, Endfield Georgina H., Adamson George C. D., Kniveton Dominic R. (2016), Seasonal rainfall variability in southeast Africa during the nineteenth century reconstructed from documentary sources, in Climatic Change, 134(4), 605-619.
Tambora 1815 as a test case for high impact volcanic eruptions: Earth system effectsTambora 1815 as a test case for high impact volcanic eruptions
Raible Christoph C., Brönnimann Stefan, Auchmann Renate, Brohan Philip, Frölicher Thomas L., Graf Hans-F., Jones Phil, Luterbacher Jürg, Muthers Stefan, Neukom Raphael, Robock Alan, Self Stephen, Sudrajat Adjat, Timmreck Claudia, Wegmann Martin (2016), Tambora 1815 as a test case for high impact volcanic eruptions: Earth system effectsTambora 1815 as a test case for high impact volcanic eruptions, in Wiley Interdisciplinary Reviews: Climate Change, 1.
Facing unprecedented drying of the Central Andes? Precipitation variability over the period AD 1000–2100
Neukom Raphael, Rohrer Mario, Calanca Pierluigi, Salzmann Nadine, Huggel Christian, Acu{ñ}}a Delia, Christie Duncan A, Morales Mariano S (2015), Facing unprecedented drying of the Central Andes? Precipitation variability over the period AD 1000–2100, in Environ. Res. Lett., 10(8), 084017-084017.
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Datasets

A global multiproxy database for temperature reconstructions of the Common Era

Author Emile-Geay, Julien; Neukom, Raphael
Publication date 05.04.2019
Persistent Identifier (PID) https://doi.org/10.6084/m9.figshare.c.3285353.v2
Repository Figshare
Abstract
Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of nat- ural climatic variability. Here we present a community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative. The database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The proxy records are from trees, ice, sediment, corals, speleothems, documentary evidence, and other archives. They range in length from 50 to 2000 years, with a median of 547 years, while temporal resolution ranges from biweekly to centennial. Nearly half of the proxy time series are significantly correlated with surface temper- ature in the HadCRUT4.2 instrumental temperature product over the period 1850-2014. Simple global composite time series show a remarkable degree of coherence between high- and low-resolution proxy archives, with broadly similar patterns across archive types, terrestrial vs marine loca- tions, and screening criteria. The database (version 2.0.0) is suited to investigations of global and regional temperature variability over the Common Era, and is shared in the Linked Paleo Data (LiPD) format, including serializations in Matlab, R and Python. Also included in this repository are: - the raw data in Linked Paleo Data (LiPD) format - instructions on how to load the data - Quality Control figures as PDF files, bundled for various regions (including a Global bundle with all 692 pages).

Hemispheric 1,000 Year Pseudoproxy Data and Temperature Reconstructions

Author Neukom, Raphael
Publication date 31.12.2018
Persistent Identifier (PID) https://www.ncdc.noaa.gov/paleo-search/study/23890
Repository NOAA paleoclimate database
Abstract
Model simulations and proxy-based reconstructions are the main tools for quantifying pre-instrumental climate variations. For some metrics such as Northern Hemisphere mean temperatures, there is remarkable agreement between models and reconstructions. For other diagnostics, such as the regional response to volcanic eruptions, or hemispheric temperature differences, substantial disagreements between data and models have been reported. Here, we assess the potential sources of these discrepancies by comparing 1000-year hemispheric temperature reconstructions based on real-world paleoclimate proxies with climate-model-based pseudoproxies. These pseudoproxy experiments (PPE) indicate that noise inherent in proxy records and the unequal spatial distribution of proxy data are the key factors in explaining the data-model differences. For example, lower inter-hemispheric correlations in reconstructions can be fully accounted for by these factors in the PPE. Noise and data sampling also partly explain the reduced amplitude of the response to external forcing in reconstructions compared to models. For other metrics, such as inter-hemispheric differences, some, although reduced, discrepancy remains. Our results suggest that improving proxy data quality and spatial coverage is the key factor to increase the quality of future climate reconstructions, while the total number of proxy records and reconstruction methodology play a smaller role.

Southern Annular Mode 1,000 Year Reconstructions

Author Dätwler, Christoph; Neukom, Raphael
Publication date 31.12.2018
Persistent Identifier (PID) https://www.ncdc.noaa.gov/paleo-search/study/23130
Repository NOAA paleoclimate database
Abstract
The Southern Annular Mode (SAM) is the leading mode of atmospheric interannual variability in the Southern Hemisphere (SH) extra-tropics. Here, we assess the stationarity of SAM spatial correlations with instrumental and paleoclimate proxy data for the past millennium. The instrumental period shows that temporal non-stationarities in SAM teleconnections are not consistent across the SH land areas. This suggests that the influence of the SAM index is modulated by regional effects. However, within key-regions with good proxy data coverage (South America, Tasmania, New Zealand), teleconnections are mostly stationary over the instrumental period. Using different stationarity criteria for proxy record selection, we provide new austral summer and annual mean SAM index reconstructions over the last millennium. Our summer SAM reconstructions are very robust to changes in proxy record selection and the selection of the calibration period, particularly on the multi-decadal timescale. In contrast, the weaker performance and lower agreement in the annual mean SAM reconstructions point towards changing teleconnection patterns that may be particularly important outside the summer months. Our results clearly portend that the temporal stationarity of the proxy-climate relationships should be taken into account in the design of comprehensive regional and hemispherical climate reconstructions. The summer SAM reconstructions show no significant relationship to solar, greenhouse gas and volcanic forcing, with the exception of an extremely strong negative anomaly following the AD 1257 Samalas eruption. Furthermore, reconstructed pre-industrial summer SAM trends are very similar to trends obtained by model control simulations. We find that recent trends in the summer SAM lie outside the 5-95% range of pre-industrial natural variability.

Multiproxy El Nino-Southern Oscillation 1,000 Year Reconstructions

Author Dätwler, Christoph; Neukom, Raphael
Publication date 04.04.2019
Persistent Identifier (PID) https://www.ncdc.noaa.gov/paleo-search/study/25891
Repository NOAA paleoclimate database
Abstract
The El Nino-Southern Oscillation (ENSO) is the earth's dominant mode of inter-annual climate variability. It alternates between warm (El Nino) and cold (La Nina) states, with global impacts on climate and society. This study provides new ENSO reconstructions based on a large, updated collection of proxy records. We use a novel reconstruction approach that employs running principal components, which allows us to take covariance changes between proxy records into account and thereby identify periods of likely teleconnection changes. Using different implementations of the principal component analysis enables us to identify periods within the last millennium when quantifications of ENSO are most robust. These periods range from 1580 to the end of the 17th century and from 1825 to present. We incorporate an assessment of consistency among our new and existing ENSO reconstructions leading to five short phases of low agreement among the reconstructions between 1700 and 1786. We find a consistent spatial pattern of proxy covariance during these four phases, differing from the structure seen over the instrumental period. This pattern points towards changes in teleconnections in the west Pacific/Australasian region, compared to the present state. Using our new reconstructions, we find a significant response of ENSO towards more La Nina-like conditions 3-5 years after major volcanic events. We further show that our new reconstructions and existing reconstructions largely agree on the state of ENSO during volcanic eruptions in the years 1695 and 1784, which helps put into perspective the climatic response to these events. During all other large volcanic eruptions of the last 1000 years, there is no reconstruction coherency with regard to the state of ENSO.

PAGES Antarctica2k Temperature Reconstructions

Author Stenni, Barbara; Neukom, Raphael
Publication date 31.12.2017
Persistent Identifier (PID) https://www.ncdc.noaa.gov/paleo-search/study/22589
Repository NOAA paleoclimate database
Abstract
Climate trends in the Antarctic region remain poorly characterized, owing to the brevity and scarcity of direct climate observations and the large magnitude of interannual to decadal-scale climate variability. Here, within the framework of the PAGES Antarctica2k working group, we build an enlarged database of ice core water stable isotope records from Antarctica, consisting of 112 records. We produce both unweighted and weighted isotopic (d18O) composites and temperature reconstructions since 0 CE, binned at 5- and 10-year resolution, for seven climatically distinct regions covering the Antarctic continent. Following earlier work of the Antarctica2k working group, we also produce composites and reconstructions for the broader regions of East Antarctica, West Antarctica and the whole continent. We use three methods for our temperature reconstructions: (i) a temperature scaling based on the d18O-temperature relationship output from an ECHAM5-wiso model simulation nudged to ERA-Interim atmospheric reanalyses from 1979 to 2013, and adjusted for the West Antarctic Ice Sheet region to borehole temperature data, (ii) a temperature scaling of the isotopic normalized anomalies to the variance of the regional reanalysis temperature and (iii) a composite-plus-scaling approach used in a previous continent-scale reconstruction of Antarctic temperature since 1 CE but applied to the new Antarctic ice core database. Our new reconstructions confirm a significant cooling trend from 0 to 1900 CE across all Antarctic regions where records extend back into the 1st millennium, with the exception of the Wilkes Land coast and Weddell Sea coast regions. Within this long-term cooling trend from 0 to 1900 CE, we find that the warmest period occurs between 300 and 1000 CE, and the coldest interval occurs from 1200 to 1900 CE. Since 1900 CE, significant warming trends are identified for the West Antarctic Ice Sheet, the Dronning Maud Land coast and the Antarctic Peninsula regions, and these trends are robust across the distribution of records that contribute to the unweighted isotopic composites and also significant in the weighted temperature reconstructions. Only for the Antarctic Peninsula is this most recent century-scale trend unusual in the context of natural variability over the last 2000 years. However, projected warming of the Antarctic continent during the 21st century may soon see significant and unusual warming develop across other parts of the Antarctic continent. The extended Antarctica2k ice core isotope database developed by this working group opens up many avenues for developing a deeper understanding of the response of Antarctic climate to natural and anthropogenic climate forcings. The first long-term quantification of regional climate in Antarctica presented herein is a basis for data-model comparison and assessments of past, present and future driving factors of Antarctic climate.

Global mean temperature reconstructions over the Common Era

Author Neukom, Raphael
Publication date 24.07.2019
Persistent Identifier (PID) 10.6084/m9.figshare.c.4507043
Repository Figshare
Abstract
Reconstruction results and input data for the paper Coherent global multi-decadal temperature variability over the Common Era in reconstructions and simulations (PAGES2k Consortium 2019, Nature Geoscience, doi: 10.1038/s41561-019-0400-0)

No evidence for globally coherent warm and cold periods over the preindustrial Common Era

Author Neukom, Raphael; Steiger, Nathan; Gómez-Navarro, Juan José; Wang, Jianghao; Werner, Johannes P.
Publication date 24.07.2019
Persistent Identifier (PID) 10.1038/s41586-019-1401-2
Repository Figshare
Abstract
Global temperature field reconstructions from Neukom et al. 2019, Nature, doi: 10.1038/s41586-019-1401-2.

Collaboration

Group / person Country
Types of collaboration
Aus2k PAGES regional group Australia (Oceania)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Exchange of personnel
Africa2k PAGES regional group South Africa (Africa)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
School of GeoSciences, University of Edinburgh Great Britain and Northern Ireland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Exchange of personnel
Dendroclimatology group, Swiss Federal Institute for Forest, Snow and Landscape Research WSL Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
School of Earth Sciences, University of Melbourne Australia (Oceania)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Exchange of personnel
Facultad de Química, Universidad de Murcia Spain (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Climate and Environmental Physics group, University of Bern Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
LOTRED-SA PAGES regional group Argentina (South America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Glaciology and Geomorphodynamics Group, University of Zurich Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Lamont-Doherty Earth Observatory of Columbia University United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Antarctica2k PAGES regional group Australia (Oceania)
- in-depth/constructive exchanges on approaches, methods or results
- Publication

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
EGU General Assembly Talk given at a conference Coherent reconstructions of Common Era global mean temperature using the latest PAGES2k data compilation 09.04.2018 Vienna, Austria Neukom Raphael;
EGU General Assembly Talk given at a conference Influence of changing predictor networks and proxy covariance on ENSO reconstructions over the last Millennium 08.04.2018 Vienna, Austria Dätwyler Christoph;
THEMES Project kickoff workshop Individual talk Data and models – from the past to the future 21.11.2017 Paris, France Neukom Raphael;
Seminar Series, University of Giessen Individual talk Southern Hemisphere temperature variability over the last 1000 years: Reconstructions, climate models and why they often disagree 07.06.2017 Giessen, Germany Neukom Raphael;
PAGES Open Science Meeting Talk given at a conference Global mean temperature reconstructions over the Common Era based on the new PAGES2k proxy database 11.05.2017 Zaragoza, Spain Neukom Raphael;
PAGES Open Science Meeting Poster The influence of proxy noise on hemispheric temperature reconstructions during the last Millennium 11.05.2017 Zaragoza, Spain Neukom Raphael;
PAGES Open Science Meeting Talk given at a conference Assessing stability of the SAM teleconnections and implications for SAM reconstructions over the past Millennium (Titel wie gehalten) ODER Instabilities of the SAM teleconnection and implications for SAM reconstructions over the past Millennium (Titel im 09.05.2017 Zaragoza, Spain Dätwyler Christoph;
Swiss Global Change Day Poster Assessing the stability of the SAM teleconnections and implications for SAM reconstructions over the past Millennium 11.04.2017 Bern, Switzerland Dätwyler Christoph;
Swiss Climate Summer School 2016 Poster Regional characteristics of the SAM and the stationarity of its teleconnections in the Southern Hemisphere 28.08.2016 Grindelwald, Switzerland Dätwyler Christoph;
Global Change Seminar, University of Edinburgh, UK Individual talk Temperature variability over the last 1000 years: A Southern Hemisphere perspective 11.05.2016 Edinburgh, Great Britain and Northern Ireland Neukom Raphael;
Swiss Global Change Day Poster Regional Characteristic of the SAM and the Stationarity of its Teleconnections in the Southern Hemisphere 12.04.2016 Bern, Switzerland Dätwyler Christoph;
Climate and Environmental Physics Seminar Individual talk Inter-hemispheric temperature variability over the last Millennium and a glimpse to the future 29.02.2016 Bern, Switzerland Neukom Raphael;
Physical Geography Seminar, University of Fribourg Individual talk Southern Hemisphere climate variability over the last 1000 years and implications for future projections 03.11.2015 Fribourg, Switzerland Neukom Raphael;
Ocean 2k Workshop Talk given at a conference Teleconnection stability ENSO sub-project. 07.10.2015 Barcelona, Spain Dätwyler Christoph;
Ocean 2k Workshop Talk given at a conference Detection of human and natural influences on the climate system: regional insights from the past Millennium 06.10.2015 Barcelona, Spain Dätwyler Christoph;
2nd Antarctica 2k workshop Individual talk Southern Hemisphere climate variability over the past 2000 years 03.09.2015 Venice, Italy Neukom Raphael;
26th European Dendroecological Fieldweek Talk given at a conference Detection of human and natural influences on the climate system: regional insights from the past Millennium 30.08.2015 Zawoja, Poland Dätwyler Christoph;


Communication with the public

Communication Title Media Place Year
Media relations: radio, television 10 vor 10 SRF 1 German-speaking Switzerland 2019
New media (web, blogs, podcasts, news feeds etc.) Podcast: The history of climate change, and making vaccines mandatory Nature Podcast International 2019
Media relations: radio, television Tagesschau SRF 1 German-speaking Switzerland 2019
Media relations: print media, online media Uni Bern widerlegt Argument von Klimaskeptikern Tages Anzeiger German-speaking Switzerland 2019
Media relations: radio, television Various Various Italian-speaking Switzerland Western Switzerland International Rhaeto-Romanic Switzerland German-speaking Switzerland 2019
Media relations: print media, online media Wie Berner Klimatologen wertvolle Informationen aus steinalten Bäumen holen Der Bund German-speaking Switzerland 2017
Media relations: print media, online media Auch in den Anden wird es trocken NZZ German-speaking Switzerland 2015
New media (web, blogs, podcasts, news feeds etc.) Lluvias en el altiplano caerían en un tercio en el futuro SciDev.net International 2015
Media relations: print media, online media Modellrechnungen zeigen: In den Anden wird es trocken Tiroler Tageszeitung International 2015
Media relations: print media, online media Stärkere Westwinde, weniger Regen Tages Anzeiger German-speaking Switzerland 2015
Media relations: print media, online media Study: Andes to lose a third of its precipitation by 2100 UPI International 2015
New media (web, blogs, podcasts, news feeds etc.) Up to 30 percent less precipitation in the Central Andes in future Phys.org International 2015
Media relations: print media, online media Wo Wasser bald mit Gold aufgewogen wird Frankfurter Allgemeine Zeitung International 2015

Associated projects

Number Title Start Funding scheme
139400 Glacier variations in southern South America: extension of the historical glacier record and connection to climate variability 01.01.2012 Fellowships for prospective researchers
131797 Cold-season climate variability in the Chilean Andes during the past millennium 01.11.2010 Ambizione
136835 High resolution reconstructions of climate variability in the sub-Antarctic during the last two millennia 01.01.2012 Ambizione
131551 Southern hemisphere atmospheric circulation variability over the past millennium: a multi-proxy reconstruction and climate model comparison 01.07.2010 Fellowships for prospective researchers

Abstract

Understanding the mechanisms of climate variability is essential for reliable projections of future climate change and thus to develop appropriate mitigation and adaption policies. However, to understand climate variations on decadal and longer timescales, the influence of different climate forcing factors needs to be known, regionally and globally. Climate forcing factors can be external (e.g. solar irradiation, volcanic eruptions and greenhouse gas concentrations) or internal atmospheric-oceanic circulation features such as the El Niño-Southern Oscillation (ENSO). Although state-of-the-art climate models have been used to project future regional and global climate change, it is still unclear how reliable regional dynamics, spatial patterns, and sensitivities to external and internal forcing factors are captured. The main obstacle in evaluating and constraining these model simulations is the lack of globally consistent and reliable spatially explicit (gridded) multi-centennial multi-proxy reconstructions of climate variability required to validate model performance at continental and regional scales. Most of the existing reconstructions focus on the Northern Hemisphere, with very preliminary regional to hemispheric reconstructions available from the Southern Hemisphere. However, instrumental data over the last 150 years have shown significant differences in climate variability and response to forcing between the two hemispheres, demonstrating that information from the ocean dominated Southern Hemisphere is required to improve our understanding of the global climate system.This project aims to advance the quantification and understanding of climate variability over the last Millennium through three complementary goals: i) improving the availability of reconstructions from the Southern Hemisphere, ii) formally attributing changes in past temperatures on hemispheric and global scales to external and internal forcing and iii) evaluating the influence of large-scale circulation on regional climate and the temporal stability of these spatial relationships (teleconnections).Aim 1: The first phase of the proposed project will fill the existing gaps in Southern Hemisphere temperature reconstructions by developing a 1000-year gridded (5°x5° spatial resolution) reconstruction with new datasets. State-of-the-art ensemble-based statistical techniques will be applied to generate robust, annually resolved reconstructions. The results will improve our global understanding of inter-annual to multi-centennial climate dynamics.Aim 2: Within the first formal “Detection and Attribution” study for the Southern Hemisphere using multi-centennial reconstructions and model simulations, key drivers of decadal to centennial temperature variability will be identified. The aim is to not only quantify the influence of human activity on climate variability, but also assess the relative importance of different natural driving factors during pre-industrial times. The results are essential for constraining estimations of the climate response to continuing anthropogenic emissions.Aim 3: The outcomes of Aim 1 and 2 will then be systematically analysed during periods of anomalous temperatures over the last millennium in reconstructions and model simulations. The spatial patterns of these anomalies will be compared to important global modes of climate variability (such as ENSO) and the temporal stability of these relations will be assessed. This will allow identifying the mechanisms leading to regionally contrasting or coherent temperature patterns. The results will provide ground-breaking insights into long-term variation of the climate system, model versus proxy coherence, and help to identify the next generation of research priorities needed to reduce uncertainties associated with past and future climate variability.The proposed project will produce a benchmark data set with very high expected impact and provide insight into regional climate variability in the global context. This is particularly relevant as regional, not global, climate data are required to quantify the direct impacts of future climate on societies, economies and the environment. This project will deliver constraints from the past, which will be a significant step towards reducing uncertainty associated with predictions of future climate change and its impacts, providing real opportunities to help inform future climate change adaptation and mitigation strategies.
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