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  • Author or Editor: Francis Zwiers x
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Gabriele Hegerl
,
Peter Stott
,
Susan Solomon
, and
Francis Zwiers

No abstract available.

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Gerald A. Meehl
,
Francis Zwiers
,
Jenni Evans
,
Thomas Knutson
,
Linda Mearns
, and
Peter Whetton

Projections of statistical aspects of weather and climate extremes can be derived from climate models representing possible future climate states. Some of the recent models have reproduced results previously reported in the Intergovernmental Panel on Climate Change (IPCC) Second Assessment Report, such as a greater frequency of extreme warm days and lower frequency of extreme cold days associated with a warmer mean climate, a decrease in diurnal temperature range associated with higher nighttime temperatures, increased precipitation intensity, midcontinent summer drying, decreasing daily variability of surface temperature in winter, and increasing variability of northern midlatitude summer surface temperatures. This reconfirmation of previous results gives an increased confidence in the credibility of the models, though agreement among models does not guarantee those changes will occur. New results since the IPCC Second Assessment Report indicate a possible increase of extreme heat stress events in a warmer climate, an increase of cooling degree days and decrease in heating degree days, an increase of precipitation extremes such that there is a decrease in return periods for 20-yr extreme precipitation events, and more detailed analyses of possible changes in 20-yr return values for extreme maximum and minimum temperatures. Additionally, recent studies are now addressing interannual and synoptic time and space scale processes that affect weather and climate extremes, such as tropical cyclones, El Niño effects, and extratropical storms. However, current climate models are not yet in agreement with respect to possible future changes in such features.

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Yujia Liu
,
Chao Li
,
Ying Sun
,
Francis Zwiers
,
Xuebin Zhang
,
Zhihong Jiang
, and
Fei Zheng
Open access
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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Gerald A. Meehl
,
Thomas Karl
,
David R. Easterling
,
Stanley Changnon
,
Roger Pielke Jr.
,
David Changnon
,
Jenni Evans
,
Pavel Ya. Groisman
,
Thomas R. Knutson
,
Kenneth E. Kunkel
,
Linda O. Mearns
,
Camille Parmesan
,
Roger Pulwarty
,
Terry Root
,
Richard T. Sylves
,
Peter Whetton
, and
Francis Zwiers

Weather and climatic extremes can have serious and damaging effects on human society and infrastructure as well as on ecosystems and wildlife. Thus, they are usually the main focus of attention of the news media in reports on climate. There are some indications from observations concerning how climatic extremes may have changed in the past. Climate models show how they could change in the future either due to natural climate fluctuations or under conditions of greenhouse gas-induced warming. These observed and modeled changes relate directly to the understanding of socioeconomic and ecological impacts related to extremes.

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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.

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