Climate over past millennia
Philip Jones,Michael E. Mann +1 more
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This paper reviewed evidence for climate change over the past several millennia from instrumental and high-resolution climate "proxy" data sources and climate modeling studies and concluded that late 20th century warmth is unprecedented at hemispheric and, likely, global scales.Abstract:
[1] We review evidence for climate change over the past several millennia from instrumental and high-resolution climate “proxy” data sources and climate modeling studies. We focus on changes over the past 1 to 2 millennia. We assess reconstructions and modeling studies analyzing a number of different climate fields, including atmospheric circulation diagnostics, precipitation, and drought. We devote particular attention to proxy-based reconstructions of temperature patterns in past centuries, which place recent large-scale warming in an appropriate longer-term context. Our assessment affirms the conclusion that late 20th century warmth is unprecedented at hemispheric and, likely, global scales. There is more tentative evidence that particular modes of climate variability, such as the El Nino/Southern Oscillation and the North Atlantic Oscillation, may have exhibited late 20th century behavior that is anomalous in a long-term context. Regional conclusions, particularly for the Southern Hemisphere and parts of the tropics where high-resolution proxy data are sparse, are more circumspect. The dramatic differences between regional and hemispheric/global past trends, and the distinction between changes in surface temperature and precipitation/drought fields, underscore the limited utility in the use of terms such as the “Little Ice Age” and “Medieval Warm Period” for describing past climate epochs during the last millennium. Comparison of empirical evidence with proxy-based reconstructions demonstrates that natural factors appear to explain relatively well the major surface temperature changes of the past millennium through the 19th century (including hemispheric means and some spatial patterns). Only anthropogenic forcing of climate, however, can explain the recent anomalous warming in the late 20th century.read more
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Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change
TL;DR: Drafting Authors: Neil Adger, Pramod Aggarwal, Shardul Agrawala, Joseph Alcamo, Abdelkader Allali, Oleg Anisimov, Nigel Arnell, Michel Boko, Osvaldo Canziani, Timothy Carter, Gino Casassa, Ulisses Confalonieri, Rex Victor Cruz, Edmundo de Alba Alcaraz, William Easterling, Christopher Field, Andreas Fischlin, Blair Fitzharris.
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Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly
Michael E. Mann,Zhihua Zhang,Scott Rutherford,Raymond S. Bradley,Malcolm K. Hughes,Drew Shindell,Caspar M. Ammann,Greg Faluvegi,Fenbiao Ni +8 more
TL;DR: The Medieval period is found to display warmth that matches or exceeds that of the past decade in some regions, but which falls well below recent levels globally, and the Little Ice Age is marked by a tendency for La Niña–like conditions in the tropical Pacific.
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Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data
TL;DR: This reconstruction of Northern Hemisphere temperatures for the past 2,000 years is reconstructed by combining low-resolution proxies with tree-ring data, using a wavelet transform technique to achieve timescale-dependent processing of the data.
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Mid- to Late Holocene climate change: an overview
Heinz Wanner,Jürg Beer,Jonathan Butikofer,Thomas J. Crowley,Ulrich Cubasch,Jacqueline Flückiger,Hugues Goosse,Martin Grosjean,Fortunat Joos,Jed O. Kaplan,Marcel Küttel,Simon A. Müller,I. Colin Prentice,Olga Solomina,Thomas F. Stocker,Pavel E. Tarasov,Mayke Wagner,Martin Widmann +17 more
TL;DR: The authors used selected proxy-based reconstructions of different climate variables, together with state-of-the-art time series of natural forcings (orbital variations, solar activity variations, large tropical volcanic eruptions, land cover and greenhouse gases), underpinned by results from GCMs and Earth System Models of Intermediate Complexity (EMICs), to establish a comprehensive explanatory framework for climate changes from the mid-Holocene (MH) to pre-industrial time.
References
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TL;DR: In this article, the authors present an overview of the climate system and its dynamics, including observed climate variability and change, the carbon cycle, atmospheric chemistry and greenhouse gases, and their direct and indirect effects.
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TL;DR: HadISST1 as mentioned in this paper replaces the global sea ice and sea surface temperature (GISST) data sets and is a unique combination of monthly globally complete fields of SST and sea ice concentration on a 1° latitude-longitude grid from 1871.
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A Pacific interdecadal climate oscillation with impacts on salmon production
TL;DR: In this article, the authors identify a robust, recurring pattern of ocean-atmosphere climate variability centered over the midlatitude North Pacific basin over the past century, the amplitude of this climate pattern has varied irregularly at interannual-to-interdecadal timescales.
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The Arctic oscillation signature in the wintertime geopotential height and temperature fields
TL;DR: The Arctic Oscillation (AO) as mentioned in this paper is the signature of modulations in the strength of the polar vortex aloft, and it resembles the NAO in many respects; but its primary center of action covers more of the Arctic, giving it a more zonally symmetric appearance.
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Teleconnections in the Geopotential Height Field during the Northern Hemisphere Winter
John M. Wallace,David S. Gutzler +1 more
TL;DR: In this paper, a review of existing literature on the subject reveals the existence of at least four such patterns: the North Atlantic and North Pacific Oscillations identified by Walker and Bliss (1932), a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes, first noted by Lorenz (1951), and what we will refer to as the Pacific/North American pattern, which has been known to operational long-range forecasters in this country since the 1950's.