The Emst Strngmann Forum

The Ernst Strungmann Forum is founded on the tenets of scientific independence and the inquisitive nature of the human mind. Through its innovative communication process, the Ernst Strungmann Forum facilitates the continual expansion of knowledge by providing a creative environment within which experts can scrutinize high-priority issues from multiple vantage points.

The themes that are selected transcend classic disciplinary boundaries; they address topics that are problem-oriented and of high-priority interest to science and society. Proposals are submitted by leading scientists active in their field and selected by the Scientific Advisory Board.

"Clouds in the Perturbed Climate System" began to take form in 2004, when Jost Heintzenberg and Bob Charlson approached me with the idea of convening a follow-up meeting to one held almost a decade earlier.1 That meeting focused on aerosol forcing: the nature and effects of aerosols, the evidence for aerosol effects, the uncertainties in climate forecasts attributable to aerosol forcing, and policy implications. As Heintzenberg and Charlson reflected, major international fi eld campaigns and basic research were stimulated by that meeting, but many issues remained unresolved. Subsequent progress had been made in understanding various parts (and their interconnections) of the Earth system. However, cloud feedbacks still pose the largest source of uncertainty in the climate system, and the resulting implications are immense.

It was decided, therefore, to convene this Ernst Strungmann Forum to assess the temporal and spatial variability of clouds in an effort to further understanding of the physical processes that control cloud evolution. In addition, the extent and nature of anthropogenic perturbations of clouds and cloud-related processes would be examined and strategies formulated to reduce critical uncertainties.

Jean-Louis Brenguier, Jim Haywood, Terry Nakajima, and Bjorn Stevens joined Heintzenberg and Charlson on the steering committee. Together they refined the key topics for discussion and selected the experts to be invited to the central meeting, which was held in Frankfurt from March 2-7, 2008.

An Ernst Strungmann Forum is a communication process—a carefully orchestrated dialog between diverse participants, each of whom assumes an active role. It is a dynamic process that unfolds over an extended period of time. The results have now been set down in this volume for further consideration.

This volume is not meant to be a consensus document. Its intent is to communicate the scope of the topics as well as the essence of the discourse that evolved. Chapters 6, 12, 18, and 24, for example, are the reports of the individual discussion groups. To draft such a report and bring it into final

Charlson, R. J., and J. Heintzenberg. 1995. Aerosol Forcing of Climate. Chichester: John Wiley & Sons.

form is no simple matter, and for this, I wish to extend a particular word of thanks to Tad Anderson, Pier Siebesma, Patrick Chuang, Graham Feingold, and Johannes Quaas. As rapporteurs of the discussion groups, their task was certainly not easy. Neither was the job of the moderators, so ably assumed by Dennis Hartmann, Jost Heintzenberg, Zev Levin, and Bill Collins. A dialog of this kind creates its own unique dynamics; invitees contributed not only their congenial personalities but also a willingness to question and probe beyond that which is already evident.

Long-held views or opinions are never easy to put aside. However, achieving this allows boundaries of the unknown to become clearer, gaps in knowledge to be recognized, and response strategies to be formulated. This is what we set out to accomplish.

A communication process of this nature requires institutional stability and an environment that guarantees free thought. Through the generous support of the Ernst Strüngmann Foundation, which was founded by Dr. Andreas and Dr. Thomas Strüngmann in honor of their father, the Ernst Strüngmann Forum is able to conduct its work in the service of science. The involvement of the Scientific Advisory Board ensures the scientific independence of the Forum, and their work is gratefully acknowledged. Additional support was received from the German Science Foundation.

Together, these partnerships have enabled this unique gathering. It is our hope that the resulting insights will stimulate further debate and direct future enquiry, as science strives to reduce the uncertainties that cloud feedbacks pose to the perturbed climate system.

Julia Lupp, Program Director

Ernst Strüngmann Forum

Frankfurt Institute for Advanced Studies (FIAS)

Ruth-Moufang-Str. 1, 60438 Frankfurt am Main, Germany

Julia Lupp

In recognition of his contributions to science and to this Ernst Strungmann Forum, and with deep respect and admiration, we dedicate this volume to our colleague and friend, Anthony Slingo.

During the final preparation of this book, Professor Anthony Slingo died suddenly, and it was a shock to all who knew him. On October 14, 2008, the University of Reading lost a leading academic; his wife, Julia, lost her soul mate and greatest fan; his daughters, Mary and Anna, lost a proud and loving father; I lost a personal friend; and the scientific community lost a great scientist who made lasting contributions to the environmental and climate sciences over many years.

Tony's work on observing and modeling the Earth's radiation budget added fundamental knowledge that advanced our understanding of how the radiative processes influence the Earth system, and how the greenhouse effect of our planet shapes our climate. More recently, Tony worked on pioneering new observations that have begun to quantify the effects of dust on the radiation balance of desert regions.

There were a number of character traits that endeared Tony to many people. His enormous sincerity spilled over into his attitudes on science. He was incredibly careful and thorough in everything he did and did not tolerate anything less than excellence. Tony pursued what he considered important with sincerity and unwavering resolve. He was direct, honest, and adept at shunning the ever-growing non-essential activities that are sadly part of an expanding overhead in science today. I admired his dogma and the way he remained true to himself over the years.

The dedication of this particular volume to the memory of Tony seems most appropriate. He clearly valued the topics addressed in this book. As was his style, he would not have attended this Ernst Strungmann Forum otherwise. Its focal topics, in many ways, mirror the important contributions that he made to science.

During the 12 years that he headed the Clouds and Climate group and then Model Parameterization group at the Hadley Center, UK Meteorological Office, Tony led many research activities that are reflected in the chapters contained within this book. He led the development of the Edward-Slingo radiative parameterization that is still in use today and which is obviously central to the cloud radiation feedbacks of the current UK Met Office model. He also developed new diagnostic approaches that eventually forged into his more recent work involving systematic comparison of GERB observations with models. Tony was involved in early aerosol indirect studies using global models, also a topic central to the theme of this book. However, he also sought more from his science and longed to become more engaged with observations and the real world than was possible, given his duties, at the Met Office. The move to the University of Reading gave him greater freedom, which made the highly successful Radagast project of today possible.

To Tony, you are missed by many.

—Graeme L. Stephens University Distinguished Professor, Colorado State University

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