Aviation and the Global Atmosphere

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Following a request from the International Civil Aviation Organization (ICAO) to assess the consequences of greenhouse gas emissions from aircraft engines, the IPCC at its Twelfth Session (Mexico City . 11-13 September 1996) decided to produce this Special Report, Aviation and the Global Atmosphere, in collaboration with the Scientific Assessment Panel to the Montreal Protocol. The task was initially a joint responsibility between IPCC Working Groups I and II but, following a change in the terms of reference of the Working Groups (Thirteenth Session of the IPCC . Maldives . 22 and 25-28 September 1997), the responsibility was transferred to IPCC Working Groups I and III, with administrative support remaining with the Technical Support Units of Working Groups I and II.

Although it is less than 100 years since the first powered flight, the aviation industry has undergone rapid growth and has become an integral and vital part of modern society. In the absence of policy intervention, the growth is likely to continue. It is therefore highly relevant to consider the current and possible future effects of aircraft engine emissions on the atmosphere. A unique aspect of this report is the integral involvement of technical experts from the aviation industry, including airlines, and airframe and engine manufacturers, alongside atmospheric scientists. This involvement has been critical in producing what we believe is the most comprehensive assessment available to date of the effects of aviation on the global atmosphere. Although this Special Report is the first IPCC report to consider a particular industrial subsector, other sectors equally deserve study.

The report considers all the gases and particles emitted by aircraft into the upper atmosphere and the role that they play in modifying the chemical properties of the atmosphere and initiating the formation of condensation trails (contrails) and cirrus clouds. The report then considers (a) how the radiative properties of the atmosphere can be modified as a result, possibly leading to climate change, and (b) how the ozone layer could be modified, leading to changes in ultraviolet radiation reaching the Earth's surface. The report also considers how potential changes in aircraft technology, air transport operations, and the institutional, regulatory, and economic framework might affect emissions in the future. The report does not deal with the effects of engine emissions on local air quality near the surface.

The objective of this Special Report is to provide accurate, unbiased, policy-relevant information to serve the aviation industry and the expert and policymaking communities. The report, in describing the current state of knowledge, also identifies areas where our understanding is inadequate and where further work is urgently required. It does not make policy recommendations or suggest policy preferences, thus is consistent with IPCC practice.

This report was compiled by 107 Lead Authors from 18 countries. Successive drafts of the report were circulated for review by experts, followed by review by governments and experts. Over 100 Contributing Authors submitted draft text and information to the Lead Authors and over 150 reviewers submitted valuable suggestions for improvement during the review process. All the comments received were carefully analyzed and assimilated into a revised document for consideration at the joint session of IPCC Working Groups I and III held in San Josť, Costa Rica, 12-14 April 1999. There, the Summary for Policymakers was approved in detail and the underlying report accepted.

We wish to express our sincere appreciation to the Report Coordinators, David Lister and Joyce Penner; to all the Coordinating Lead Authors, Lead Authors, and Review Editors whose expertise, diligence, and patience have underpinned the successful completion of this report; and to the many contributors and reviewers for their valuable and painstaking dedication and work. We thank the Steering Committee for their wise counsel and guidance throughout the preparation of the report. We are grateful to:

In particular, we are grateful to John Crayston (ICAO), Steve Pollonais (government of Trinidad and Tobago), Leonie Dobbie (IATA), and Max Campos (government of Costa Rica) for their taking on the demanding burden of arranging for these meetings.

We also thank Anne Murrill of the Working Group I Technical Support Unit and Sandy MacCracken of the Working Group II Technical Support Unit for their tireless and good humored support throughout the preparation of the report. Other members of the Technical Support Units of Working Groups I and II also provided much assistance, including Richard Moss, Mack McFarland, Maria Noguer, Laura Van Wie McGrory, Neil Leary, Paul van der Linden, and Flo Ormond. The staff of the IPCC Secretariat, Rudie Bourgeois, Cecilia Tanikie, and Chantal Ettori, provided logistical support for all government liaison and travel of experts from the developing and transitional economy countries.

Robert Watson, IPCC Chairman
John Houghton, Co-Chair of IPCC Working Group I
Ding Yihui, Co-Chair of IPCC Working Group I
Bert Metz, Co-Chair of IPCC Working Group III
Ogunlade Davidson, Co-Chair of IPCC Working Group III
N. Sundararaman, IPCC Secretary
David Griggs, IPCC Working Group I TSU
David Dokken, IPCC Working Group II TSU

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