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Ghassem Asrar
,
Sandrine Bony
,
Olivier Boucher
,
Antonio Busalacchi
,
Anny Cazenave
,
Mark Dowell
,
Greg Flato
,
Gabi Hegerl
,
Erland Källén
,
Teruyuki Nakajima
,
Alain Ratier
,
Roger Saunders
,
Julia Slingo
,
Byung-Ju Sohn
,
Johannes Schmetz
,
Bjorn Stevens
,
Peiqun Zhang
, and
Francis Zwiers
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Stefan Brönnimann
,
Rob Allan
,
Christopher Atkinson
,
Roberto Buizza
,
Olga Bulygina
,
Per Dahlgren
,
Dick Dee
,
Robert Dunn
,
Pedro Gomes
,
Viju O. John
,
Sylvie Jourdain
,
Leopold Haimberger
,
Hans Hersbach
,
John Kennedy
,
Paul Poli
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Jouni Pulliainen
,
Nick Rayner
,
Roger Saunders
,
Jörg Schulz
,
Alexander Sterin
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Alexander Stickler
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Holly Titchner
,
Maria Antonia Valente
,
Clara Ventura
, and
Clive Wilkinson

Abstract

Global dynamical reanalyses of the atmosphere and ocean fundamentally rely on observations, not just for the assimilation (i.e., for the definition of the state of the Earth system components) but also in many other steps along the production chain. Observations are used to constrain the model boundary conditions, for the calibration or uncertainty determination of other observations, and for the evaluation of data products. This requires major efforts, including data rescue (for historical observations), data management (including metadatabases), compilation and quality control, and error estimation. The work on observations ideally occurs one cycle ahead of the generation cycle of reanalyses, allowing the reanalyses to make full use of it. In this paper we describe the activities within ERA-CLIM2, which range from surface, upper-air, and Southern Ocean data rescue to satellite data recalibration and from the generation of snow-cover products to the development of a global station data metadatabase. The project has not produced new data collections. Rather, the data generated has fed into global repositories and will serve future reanalysis projects. The continuation of this effort is first contingent upon the organization of data rescue and also upon a series of targeted research activities to address newly identified in situ and satellite records.

Open access
Sarah J. Doherty
,
Stephan Bojinski
,
Ann Henderson-Sellers
,
Kevin Noone
,
David Goodrich
,
Nathaniel L. Bindoff
,
John A. Church
,
Kathy A. Hibbard
,
Thomas R. Karl
,
Lucka Kajfez-Bogataj
,
Amanda H. Lynch
,
David E. Parker
,
I. Colin Prentice
,
Venkatachalam Ramaswamy
,
Roger W. Saunders
,
Mark Stafford Smith
,
Konrad Steffen
,
Thomas F. Stocker
,
Peter W. Thorne
,
Kevin E. Trenberth
,
Michel M. Verstraete
, and
Francis W. Zwiers

The Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) concluded that global warming is “unequivocal” and that most of the observed increase since the mid-twentieth century is very likely due to the increase in anthropogenic greenhouse gas concentrations, with discernible human influences on ocean warming, continental-average temperatures, temperature extremes, wind patterns, and other physical and biological indicators, impacting both socioeconomic and ecological systems. It is now clear that we are committed to some level of global climate change, and it is imperative that this be considered when planning future climate research and observational strategies. The Global Climate Observing System program (GCOS), the World Climate Research Programme (WCRP), and the International Geosphere-Biosphere Programme (IGBP) therefore initiated a process to summarize the lessons learned through AR4 Working Groups I and II and to identify a set of high-priority modeling and observational needs. Two classes of recommendations emerged. First is the need to improve climate models, observational and climate monitoring systems, and our understanding of key processes. Second, the framework for climate research and observations must be extended to document impacts and to guide adaptation and mitigation efforts. Research and observational strategies specifically aimed at improving our ability to predict and understand impacts, adaptive capacity, and societal and ecosystem vulnerabilities will serve both purposes and are the subject of the specific recommendations made in this paper.

Full access
Paul Poli
,
Dick P. Dee
,
Roger Saunders
,
Viju O. John
,
Peter Rayer
,
Jörg Schulz
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Kenneth Holmlund
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Dorothee Coppens
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Dieter Klaes
,
James E. Johnson
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Asghar E. Esfandiari
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Irina V. Gerasimov
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Emily B. Zamkoff
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Atheer F. Al-Jazrawi
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David Santek
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Mirko Albani
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Pascal Brunel
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Karsten Fennig
,
Marc Schröder
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Shinya Kobayashi
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Dieter Oertel
,
Wolfgang Döhler
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Dietrich Spänkuch
, and
Stephan Bojinski

Abstract

To better understand the impacts of climate change, environmental monitoring capabilities must be enhanced by deploying additional and more accurate satellite- and ground-based (including in situ) sensors. In addition, reanalysis of observations collected decades ago but long forgotten can unlock precious information about the recent past. Historical, in situ observations mainly cover densely inhabited areas and frequently traveled routes. In contrast, large selections of early meteorological satellite data, waiting to be exploited today, provide information about remote areas unavailable from any other source. When initially collected, these satellite data posed great challenges to transmission and archiving facilities. As a result, data access was limited to the main teams of scientific investigators associated with the instruments. As archive media have aged, so have the mission scientists and other pioneers of satellite meteorology, who sometimes retired in possession of unique and unpublished information.

This paper presents examples of recently recovered satellite data records, including satellite imagery, early infrared hyperspectral soundings, and early microwave humidity soundings. Their value for climate applications today can be realized using methods and techniques that were not yet available when the data were first collected, including efficient and accurate observation simulators and data assimilation into reanalyses. Modern technical infrastructure allows serving entire mission datasets online, enabling easy access and exploration by a broad range of users, including new and old generations of climate scientists.

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Roberto Buizza
,
Stefan Brönnimann
,
Leopold Haimberger
,
Patrick Laloyaux
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Matthew J. Martin
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Manuel Fuentes
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Magdalena Alonso-Balmaseda
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Andreas Becker
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Michael Blaschek
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Per Dahlgren
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Eric de Boisseson
,
Dick Dee
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Marie Doutriaux-Boucher
,
Xiangbo Feng
,
Viju O. John
,
Keith Haines
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Sylvie Jourdain
,
Yuki Kosaka
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Daniel Lea
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Florian Lemarié
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Michael Mayer
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Palmira Messina
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Coralie Perruche
,
Philippe Peylin
,
Jounie Pullainen
,
Nick Rayner
,
Elke Rustemeier
,
Dinand Schepers
,
Roger Saunders
,
Jörg Schulz
,
Alexander Sterin
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Sebastian Stichelberger
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Andrea Storto
,
Charles-Emmanuel Testut
,
Maria-Antóonia Valente
,
Arthur Vidard
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Nicolas Vuichard
,
Anthony Weaver
,
James While
, and
Markus Ziese

Abstract

The European Reanalysis of Global Climate Observations 2 (ERA-CLIM2) is a European Union Seventh Framework Project started in January 2014 and due to be completed in December 2017. It aims to produce coupled reanalyses, which are physically consistent datasets describing the evolution of the global atmosphere, ocean, land surface, cryosphere, and the carbon cycle. ERA-CLIM2 has contributed to advancing the capacity for producing state-of-the-art climate reanalyses that extend back to the early twentieth century. ERA-CLIM2 has led to the generation of the first European ensemble of coupled ocean, sea ice, land, and atmosphere reanalyses of the twentieth century. The project has funded work to rescue and prepare observations and to advance the data-assimilation systems required to generate operational reanalyses, such as the ones planned by the European Union Copernicus Climate Change Service. This paper summarizes the main goals of the project, discusses some of its main areas of activities, and presents some of its key results.

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