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Joelle Gergis

Bio: Joelle Gergis is an academic researcher from Australian National University. The author has contributed to research in topics: Climate change & Multivariate ENSO index. The author has an hindex of 25, co-authored 63 publications receiving 3392 citations. Previous affiliations of Joelle Gergis include University of Melbourne & University of New South Wales.


Papers
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Journal ArticleDOI
Moinuddin Ahmed1, Kevin J. Anchukaitis2, Kevin J. Anchukaitis3, Asfawossen Asrat4, H. P. Borgaonkar5, Martina Braida6, Brendan M. Buckley3, Ulf Büntgen7, Brian M. Chase8, Brian M. Chase9, Duncan A. Christie10, Duncan A. Christie11, Edward R. Cook3, Mark A. J. Curran12, Mark A. J. Curran13, Henry F. Diaz14, Jan Esper15, Ze-Xin Fan16, Narayan Prasad Gaire17, Quansheng Ge18, Joelle Gergis19, J. Fidel González-Rouco20, Hugues Goosse21, Stefan W. Grab22, Nicholas E. Graham23, Rochelle Graham23, Martin Grosjean24, Sami Hanhijärvi25, Darrell S. Kaufman26, Thorsten Kiefer, Katsuhiko Kimura27, Atte Korhola25, Paul J. Krusic28, Antonio Lara10, Antonio Lara11, Anne-Marie Lézine29, Fredrik Charpentier Ljungqvist28, Andrew Lorrey30, Jürg Luterbacher31, Valérie Masson-Delmotte29, Danny McCarroll32, Joseph R. McConnell33, Nicholas P. McKay26, Mariano S. Morales34, Andrew D. Moy12, Andrew D. Moy13, Robert Mulvaney35, Ignacio A. Mundo34, Takeshi Nakatsuka36, David J. Nash22, David J. Nash37, Raphael Neukom7, Sharon E. Nicholson38, Hans Oerter39, Jonathan G. Palmer40, Jonathan G. Palmer41, Steven J. Phipps40, María Prieto32, Andrés Rivera42, Masaki Sano36, Mirko Severi43, Timothy M. Shanahan44, Xuemei Shao18, Feng Shi, Michael Sigl33, Jason E. Smerdon3, Olga Solomina45, Eric J. Steig46, Barbara Stenni6, Meloth Thamban47, Valerie Trouet48, Chris S. M. Turney40, Mohammed Umer4, Tas van Ommen12, Tas van Ommen13, Dirk Verschuren49, A. E. Viau50, Ricardo Villalba34, Bo Møllesøe Vinther51, Lucien von Gunten, Sebastian Wagner, Eugene R. Wahl14, Heinz Wanner24, Johannes P. Werner31, James W. C. White52, Koh Yasue53, Eduardo Zorita 
Federal Urdu University1, Woods Hole Oceanographic Institution2, Columbia University3, Addis Ababa University4, Indian Institute of Tropical Meteorology5, University of Trieste6, Swiss Federal Institute for Forest, Snow and Landscape Research7, University of Montpellier8, University of Bergen9, Austral University of Chile10, University of Chile11, Australian Antarctic Division12, University of Tasmania13, National Oceanic and Atmospheric Administration14, University of Mainz15, Xishuangbanna Tropical Botanical Garden16, Nepal Academy of Science and Technology17, Chinese Academy of Sciences18, University of Melbourne19, Complutense University of Madrid20, Université catholique de Louvain21, University of the Witwatersrand22, Hydrologic Research Center23, University of Bern24, University of Helsinki25, Northern Arizona University26, Fukushima University27, Stockholm University28, Université Paris-Saclay29, National Institute of Water and Atmospheric Research30, University of Giessen31, Swansea University32, Desert Research Institute33, National Scientific and Technical Research Council34, British Antarctic Survey35, Nagoya University36, University of Brighton37, Florida State University38, Alfred Wegener Institute for Polar and Marine Research39, University of New South Wales40, University of Exeter41, Centro de Estudios Científicos42, University of Florence43, University of Texas at Austin44, Russian Academy of Sciences45, University of Washington46, National Centre for Antarctic and Ocean Research47, University of Arizona48, Ghent University49, University of Ottawa50, University of Copenhagen51, University of Colorado Boulder52, Shinshu University53
TL;DR: The authors reconstructed past temperatures for seven continental-scale regions during the past one to two millennia and found that the most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend, which ended late in the nineteenth century.
Abstract: Past global climate changes had strong regional expression To elucidate their spatio-temporal pattern, we reconstructed past temperatures for seven continental-scale regions during the past one to two millennia The most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend, which ended late in the nineteenth century At multi-decadal to centennial scales, temperature variability shows distinctly different regional patterns, with more similarity within each hemisphere than between them There were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age, but all reconstructions show generally cold conditions between ad 1580 and 1880, punctuated in some regions by warm decades during the eighteenth century The transition to these colder conditions occurred earlier in the Arctic, Europe and Asia than in North America or the Southern Hemisphere regions Recent warming reversed the long-term cooling; during the period ad 1971–2000, the area-weighted average reconstructed temperature was higher than any other time in nearly 1,400 years

885 citations

Journal ArticleDOI
TL;DR: The Tripole Index (TPI) as discussed by the authors is a non-PC-based index for tracking decadal SST variability associated with the IPO, which is based on the difference between SST averaged over the central equatorial Pacific and the average of the SSTA in the Northwest and Southwest Pacific.
Abstract: A new index is developed for the Interdecadal Pacific Oscillation, termed the IPO Tripole Index (TPI). The IPO is associated with a distinct ‘tripole’ pattern of sea surface temperature anomalies (SSTA), with three large centres of action and variations on decadal timescales, evident in the second principal component (PC) of low-pass filtered global SST. The new index is based on the difference between the SSTA averaged over the central equatorial Pacific and the average of the SSTA in the Northwest and Southwest Pacific. The TPI is an easily calculated, non-PC-based index for tracking decadal SST variability associated with the IPO. The TPI time series bears a close resemblance to previously published PC-based indices and has the advantages of being simpler to compute and more consistent with indices used to track the El Nino–Southern Oscillation (ENSO), such as Nino 3.4. The TPI also provides a simple metric in physical units of °C for evaluating decadal and interdecadal variability of SST fields in a straightforward manner, and can be used to evaluate the skill of dynamical decadal prediction systems. Composites of SST and mean sea level pressure anomalies reveal that the IPO has maintained a broadly stable structure across the seven most recent positive and negative epochs that occurred during 1870–2013. The TPI is shown to be a robust and stable representation of the IPO phenomenon in instrumental records, with relatively more variance in decadal than shorter timescales compared to Nino 3.4, due to the explicit inclusion of off-equatorial SST variability associated with the IPO.

480 citations

Journal ArticleDOI
TL;DR: The 20CRv2c dataset as mentioned in this paper is the first ensemble of sub-daily global atmospheric conditions spanning over 100 years, which provides a best estimate of the weather at any given place and time as well as an estimate of its confidence and uncertainty.
Abstract: Historical reanalyses that span more than a century are needed for a wide range of studies, from understanding large‐scale climate trends to diagnosing the impacts of individual historical extreme weather events. The Twentieth Century Reanalysis (20CR) Project is an effort to fill this need. It is supported by the National Oceanic and Atmospheric Administration (NOAA), the Cooperative Institute for Research in Environmental Sciences (CIRES), and the U.S. Department of Energy (DOE), and is facilitated by collaboration with the international Atmospheric Circulation Reconstructions over the Earth initiative. 20CR is the first ensemble of sub‐daily global atmospheric conditions spanning over 100 years. This provides a best estimate of the weather at any given place and time as well as an estimate of its confidence and uncertainty. While extremely useful, version 2c of this dataset (20CRv2c) has several significant issues, including inaccurate estimates of confidence and a global sea level pressure bias in the mid‐19th century. These and other issues can reduce its effectiveness for studies at many spatial and temporal scales. Therefore, the 20CR system underwent a series of developments to generate a significant new version of the reanalysis. The version 3 system (NOAA‐CIRES‐DOE 20CRv3) uses upgraded data assimilation methods including an adaptive inflation algorithm; has a newer, higher‐resolution forecast model that specifies dry air mass; and assimilates a larger set of pressure observations. These changes have improved the ensemble‐based estimates of confidence, removed spin‐up effects in the precipitation fields, and diminished the sea‐level pressure bias. Other improvements include more accurate representations of storm intensity, smaller errors, and large‐scale reductions in model bias. The 20CRv3 system is comprehensively reviewed, focusing on the aspects that have ameliorated issues in 20CRv2c. Despite the many improvements, some challenges remain, including a systematic bias in tropical precipitation and time‐varying biases in southern high‐latitude pressure fields.

409 citations

Journal ArticleDOI
TL;DR: In this paper, a number of percentile-based palaeoclimate reconstructions were used to isolate signals of both phases of El Nino-Southern Oscillation (ENSO).
Abstract: Reconstructions of past climate are important for providing a historical context for evaluating the nature of 20th century climate change. Here, a number of percentile-based palaeoclimate reconstructions were used to isolate signals of both phases of El Nino-Southern Oscillation (ENSO). A total of 92 (82) El Nino (La Nina) events were reconstructed since A.D. 1525. Significantly, we introduce the most comprehensive La Nina event record compiled to date. This annual record of ENSO events can now be used for independent verification of climate model simulations, reconstructions of ENSO indices and as a chronological control for archaeologists/social scientists interested in human responses to past climate events. Although extreme ENSO events are seen throughout the 478-year ENSO recon- struction, approximately 43% of extreme and 28% of all protracted ENSO events (i.e. both El Nino and La Nina phase) occur in the 20th century. The post-1940 period alone accounts for 30% of extreme ENSO years observed since A.D. 1525. These results suggest that ENSO may operate differently under natural (pre-industrial) and anthropogenic background states. As evidence of stresses on water supply, agriculture and natural ecosystems caused by climate change strengthens, studies into how ENSO will operate under global warming should be a global research priority.

297 citations

Journal ArticleDOI
Julien Emile-Geay1, Nicholas P. McKay2, Darrell S. Kaufman2, Lucien von Gunten, Jianghao Wang3, Kevin J. Anchukaitis4, Nerilie J. Abram5, Jason A. Addison6, Mark A. J. Curran7, Mark A. J. Curran8, Michael N. Evans9, Benjamin J. Henley10, Zhixin Hao, Belen Martrat11, Belen Martrat12, Helen McGregor13, Raphael Neukom14, Gregory T. Pederson6, Barbara Stenni15, Kaustubh Thirumalai16, Johannes P. Werner17, Chenxi Xu18, Dmitry Divine19, Bronwyn C. Dixon10, Joelle Gergis10, Ignacio A. Mundo20, Takeshi Nakatsuka, Steven J. Phipps7, Cody C. Routson2, Eric J. Steig21, Jessica E. Tierney4, Jonathan J. Tyler22, Kathryn Allen10, Nancy A. N. Bertler23, Jesper Björklund24, Brian M. Chase25, Min Te Chen26, Edward R. Cook27, Rixt de Jong14, Kristine L. DeLong28, Daniel A. Dixon29, Alexey A. Ekaykin30, Alexey A. Ekaykin31, Vasile Ersek32, Helena L. Filipsson33, Pierre Francus34, Mandy Freund10, Massimo Frezzotti, Narayan Prasad Gaire35, Narayan Prasad Gaire36, Konrad Gajewski37, Quansheng Ge, Hugues Goosse38, Anastasia Gornostaeva, Martin Grosjean14, Kazuho Horiuchi39, Anne Hormes40, Katrine Husum19, Elisabeth Isaksson19, Selvaraj Kandasamy41, Kenji Kawamura42, Kenji Kawamura43, K. Halimeda Kilbourne9, Nalan Koc19, Guillaume Leduc44, Hans W. Linderholm40, Andrew Lorrey45, Vladimir Mikhalenko46, P. Graham Mortyn47, Hideaki Motoyama42, Andrew D. Moy8, Andrew D. Moy7, Robert Mulvaney48, Philipp Munz49, David J. Nash50, David J. Nash51, Hans Oerter52, Thomas Opel52, Anais Orsi53, Dmitriy V. Ovchinnikov54, Trevor J. Porter55, Heidi A. Roop56, Casey Saenger21, Masaki Sano, David J. Sauchyn38, Krystyna M. Saunders57, Krystyna M. Saunders14, Marit-Solveig Seidenkrantz58, Mirko Severi59, Xuemei Shao, Marie-Alexandrine Sicre60, Michael Sigl61, Kate E. Sinclair, Scott St. George62, Jeannine-Marie St. Jacques63, Jeannine-Marie St. Jacques64, Meloth Thamban65, Udya Kuwar Thapa62, Elizabeth R. Thomas48, Chris S. M. Turney66, Ryu Uemura67, A. E. Viau37, Diana Vladimirova31, Diana Vladimirova30, Eugene R. Wahl68, James W. C. White69, Zicheng Yu70, Jens Zinke71, Jens Zinke72 
University of Southern California1, Northern Arizona University2, MathWorks3, University of Arizona4, Australian National University5, United States Geological Survey6, University of Tasmania7, Australian Antarctic Division8, University of Maryland, College Park9, University of Melbourne10, University of Cambridge11, Spanish National Research Council12, University of Wollongong13, University of Bern14, Ca' Foscari University of Venice15, University of Texas at Austin16, University of Bergen17, Chinese Academy of Sciences18, Norwegian Polar Institute19, National University of Cuyo20, University of Washington21, University of Adelaide22, Victoria University of Wellington23, Swiss Federal Institute for Forest, Snow and Landscape Research24, University of Montpellier25, National Taiwan Ocean University26, Columbia University27, Louisiana State University28, University of Maine29, Saint Petersburg State University30, Arctic and Antarctic Research Institute31, Northumbria University32, Lund University33, Institut national de la recherche scientifique34, Nepal Academy of Science and Technology35, Tribhuvan University36, University of Ottawa37, Université catholique de Louvain38, Hirosaki University39, University of Gothenburg40, Xiamen University41, National Institute of Polar Research42, Japan Agency for Marine-Earth Science and Technology43, Aix-Marseille University44, National Institute of Water and Atmospheric Research45, Russian Academy of Sciences46, Autonomous University of Barcelona47, British Antarctic Survey48, University of Tübingen49, University of the Witwatersrand50, University of Brighton51, Alfred Wegener Institute for Polar and Marine Research52, Université Paris-Saclay53, Sukachev Institute of Forest54, University of Toronto55, University at Buffalo56, Australian Nuclear Science and Technology Organisation57, Aarhus University58, University of Florence59, Pierre-and-Marie-Curie University60, Paul Scherrer Institute61, University of Minnesota62, Concordia University63, University of Regina64, National Centre for Antarctic and Ocean Research65, University of New South Wales66, University of the Ryukyus67, National Oceanic and Atmospheric Administration68, University of Colorado Boulder69, Lehigh University70, Free University of Berlin71, Australian Institute of Marine Science72
TL;DR: A community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative, 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.
Abstract: Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural 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 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 HadCRUT4.2 surface temperature over the period 1850–2014. Global temperature composites show a remarkable degree of coherence between high- and low-resolution archives, with broadly similar patterns across archive types, terrestrial versus marine locations, and screening criteria. The database 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.

260 citations


Cited by
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Journal ArticleDOI
12 Mar 2015-Nature
TL;DR: The authors reviewed the historical genesis of the Anthropocene Epoch idea and assessed anthropogenic signatures in the geological record against the formal requirements for the recognition of a new epoch, finding that of the various proposed dates two do appear to conform to the criteria to mark the beginning of the anthropocene: 1610 and 1964.
Abstract: Time is divided by geologists according to marked shifts in Earth's state. Recent global environmental changes suggest that Earth may have entered a new human-dominated geological epoch, the Anthropocene. Here we review the historical genesis of the idea and assess anthropogenic signatures in the geological record against the formal requirements for the recognition of a new epoch. The evidence suggests that of the various proposed dates two do appear to conform to the criteria to mark the beginning of the Anthropocene: 1610 and 1964. The formal establishment of an Anthropocene Epoch would mark a fundamental change in the relationship between humans and the Earth system.

1,578 citations

Journal ArticleDOI
08 Jan 2016-Science
TL;DR: C climatic, biological, and geochemical signatures of human activity in sediments and ice cores, Combined with deposits of new materials and radionuclides, as well as human-caused modification of sedimentary processes, the Anthropocene stands alone stratigraphically as a new epoch beginning sometime in the mid–20th century.
Abstract: Human activity is leaving a pervasive and persistent signature on Earth. Vigorous debate continues about whether this warrants recognition as a new geologic time unit known as the Anthropocene. We review anthropogenic markers of functional changes in the Earth system through the stratigraphic record. The appearance of manufactured materials in sediments, including aluminum, plastics, and concrete, coincides with global spikes in fallout radionuclides and particulates from fossil fuel combustion. Carbon, nitrogen, and phosphorus cycles have been substantially modified over the past century. Rates of sea-level rise and the extent of human perturbation of the climate system exceed Late Holocene changes. Biotic changes include species invasions worldwide and accelerating rates of extinction. These combined signals render the Anthropocene stratigraphically distinct from the Holocene and earlier epochs.

1,441 citations

Journal ArticleDOI
TL;DR: Efforts to reverse global trends in freshwater degradation now depend on bridging an immense gap between the aspirations of conservation biologists and the accelerating rate of species endangerment.
Abstract: In the 12 years since Dudgeon et al. (2006) reviewed major pressures on freshwater ecosystems, the biodiversity crisis in the world’s lakes, reservoirs, rivers, streams and wetlands has deepened. While lakes, reservoirs and rivers cover only 2.3% of the Earth’s surface, these ecosystems host at least 9.5% of the Earth’s described animal species. Furthermore, using the World Wide Fund for Nature’s Living Planet Index, freshwater population declines (83% between 1970 and 2014) continue to outpace contemporaneous declines in marine or terrestrial systems. The Anthropocene has brought multiple new and varied threats that disproportionately impact freshwater systems. We document 12 emerging threats to freshwater biodiversity that are either entirely new since 2006 or have since intensified: (i) changing climates; (ii) e-commerce and invasions; (iii) infectious diseases; (iv) harmful algal blooms; (v) expanding hydropower; (vi) emerging contaminants; (vii) engineered nanomaterials; (viii) microplastic pollution; (ix) light and noise; (x) freshwater salinisation; (xi) declining calcium; and (xii) cumulative stressors. Effects are evidenced for amphibians, fishes, invertebrates, microbes, plants, turtles and waterbirds, with potential for ecosystem-level changes through bottom-up and top-down processes. In our highly uncertain future, the net effects of these threats raise serious concerns for freshwater ecosystems. However, we also highlight opportunities for conservation gains as a result of novel management tools (e.g. environmental flows, environmental DNA) and specific conservation-oriented actions (e.g. dam removal, habitat protection policies,managed relocation of species) that have been met with varying levels of success.Moving forward, we advocate hybrid approaches that manage fresh waters as crucial ecosystems for human life support as well as essential hotspots of biodiversity and ecological function. Efforts to reverse global trends in freshwater degradation now depend on bridging an immense gap between the aspirations of conservation biologists and the accelerating rate of species endangerment.

1,230 citations

01 Apr 2016
TL;DR: The evidence suggests that of the various proposed dates two do appear to conform to the criteria to mark the beginning of the Anthropocene: 1610 and 1964.
Abstract: Time is divided by geologists according to marked shifts in Earth's state. Recent global environmental changes suggest that Earth may have entered a new human-dominated geological epoch, the Anthropocene. Here we review the historical genesis of the idea and assess anthropogenic signatures in the geological record against the formal requirements for the recognition of a new epoch. The evidence suggests that of the various proposed dates two do appear to conform to the criteria to mark the beginning of the Anthropocene: 1610 and 1964. The formal establishment of an Anthropocene Epoch would mark a fundamental change in the relationship between humans and the Earth system.

1,173 citations

Journal ArticleDOI
TL;DR: This paper showed that strengthening trade winds caused a reduction in the 2012 global average surface air temperature of 0.1 −0.2°C, which is a result of increased subsurface ocean heat uptake.
Abstract: The slowdown in global average surface warming has recently been linked to sea surface cooling in the eastern Pacific Ocean. This work shows that strengthening trade winds caused a reduction in the 2012 global average surface air temperature of 0.1–0.2 °C. This may account for much of the warming hiatus and is a result of increased subsurface ocean heat uptake.

1,151 citations