Quantifying expert consensus against the existence of a secret, large-scale atmospheric spraying program

Aug 10, 2016

Nearly 17% of people in an international survey said they believed the existence of a secret large-scale atmospheric program (SLAP) to be true or partly true. SLAP is commonly referred to as ‘chemtrails’ or ‘covert geoengineering’, and has led to a number of websites purported to show evidence of widespread chemical spraying linked to negative impacts on human health and the environment.

To address these claims, we surveyed two groups of experts—atmospheric chemists with expertise in condensation trails and geochemists working on atmospheric deposition of dust and pollution—to scientifically evaluate for the first time the claims of SLAP theorists. Results show that 76 of the 77 scientists (98.7%) that took part in this study said they had not encountered evidence of a SLAP, and that the data cited as evidence could be explained through other factors, including well-understood physics and chemistry associated with aircraft contrails and atmospheric aerosols.

Our goal is not to sway those already convinced that there is a secret, large-scale spraying program—who often reject counter-evidence as further proof of their theories—but rather to establish a source of objective science that can inform public discourse.

published in Environmental Research Letters

Christine Shearer *†, Mick West §, Ken Caldeira ‡ and Steven J. Davis *†

* Near Zero

† University of California, Irvine, Department of Earth System Science

§ Metabunk.org

‡ Carnegie Institution for Science, Department of Global Ecology

Expert participants

78 experts participated in the elicitations for this report:

Andrew Carleton

Penn State University

Andrew Heidinger

National Oceanic and Atmospheric Administration

Andrew Heymsfield

National Center for Atmospheric Research (NCAR)

Andrew J. Weinheimer

National Center for Atmospheric Research

Anne-Catherine Pierson-Wickmann

University of Rennes 1

Brian A. Ridley

National Aeronautics and Space Administration

Bruce Anderson

National Aeronautics and Space Administration

Bryan Baum

University of Wisconsin-Madison

Carmen Nezat

Eastern Washington University

Carol Kendall

US Geological Survey

Charles A. Brock

National Oceanic and Atmospheric Administration

Charles E. Kolb

Aerodyne Research

Chris Measures

University of Hawaii

Christine Fichter

German Aerospace Center (DLR)

Christopher Hissler

Gabriel Lippmann Public Research Centre

Christos Zerefos

University of Athens

Clifton Buck

Franklin College

Cynthia Twohy

NorthWest Research Associates

Daniel Engstrom

University of Minnesota

Darrel Baumgardner

Droplet Measurement Technologies

David Doelling

National Aeronautics and Space Administration

David Grantz

University of California at Riverside

David J. Travis

University of Wisconsin-Whitewater

David Kratz

National Aeronautics and Space Administration

David Lee

Manchester Metropolitan University

David Lewellen

West Virginia University

Dominik Weiss

Imperial College London

Donald P. Garber

National Aeronautics and Space Administration

Eleftheratos Konstantinos

University of Athens

Gaby Radel

University of Reading

Guy Febvre

Observatory of Atmospheric Physics at Clermont-Ferrand

Hartmut Grassl

Max Planck Institute for Meteorology

Heleen de Wit

Norwegian Institute for Water Research

Jack Dibb

University of New Hampshire

Jan Kramers

University of Johannesburg

Jill Schrlau

Oregon State University

Joanna Clark

University of Reading

Josef Hejzlar

Institute of Hydrobiology

Karen Rosenlof

National Oceanic and Atmospheric Administration

Kiminori Shitashima

Kyushu University

Klaus Gierens

German Aerospace Center (DLR)

Larry Miloshevich

Milo Scientific

Lubos Boruvka

Czech University of Life Sciences Prague

Marjorie Schulz

US Geological Survey

Mark Smits

Hasselt University

Markus Garhammer


Matt Kulp

US National Park Service

Matthias Tesche

Stockholm University

Michael Ponater

German Aerospace Center (DLR)

Michael Prather

University of California at Irvine

Nicolas Belanger

University of Quebec

Otto Klemm

University of Muenster

Patrick Minnis

National Aeronautics & Space Administration

Pavel Rosendorf

T. G. Masaryk Water Research Institute

Piers Forster

University of Leeds

R. Paul Lawson

Stratton Park Engineering Company

Rabi Palikonda

National Aeronautics & Space Administration

Reinhold Busen

German Aerospace Center (DLR)

Robert Duce

Texas A&M University

Robert Sausen

Institute of Atmospheric Physics

Robert Talbot

University of Houston

Rolf David Vogt

University of Oslo

Ru-Shan Gao

National Oceanic and Atmospheric Administration

Scott Bailey

US Forest Service

Sonia M. Kreidenweis

Colorado State University

Stephan Bakan

Max Planck Institute for Meteorology

Steve Howell

University of Hawaii

Tatiana Khokhlova

University of Washington

Thilo Stilp

European Aviation Group for Occupational Safety and Health

Tomas Navratil

Czech Geological Survey

Tove Svenby

Norwegian Institute for Air Research

Ulrich Schumann

Institute of Atmospheric Physics

Ulrike Burkhardt

German Aerospace Center (DLR)

Volker Grewe

Institute of Atmospheric Physics

William L. Smith

National Aeronautics and Space Administration

William Landing

Florida State University

Wim de Vries

Wageningen University

photo credit: Mick West