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Impact of Aviation on Climate

Research Priorities

Guy P. Brasseur and Mohan Gupta

Though presently small in magnitude, aviation's future impact on climate will likely increase with the absence of effective mitigation measures. With the exception of CO2 emissions, climate impacts of aviation emissions are quite uncertain, and there are scientific gaps that need to be addressed to guide decision making. An objective of the Next Generation Air Transportation System is to limit or reduce aviation's impact on climate. Therefore, the Federal Aviation Administration has developed the Aviation Climate Change Research Initiative (ACCRI) to address key scientific gaps and reduce uncertainties while providing timely scientific input to advance and implement mitigation measures. This paper provides a brief overview of the priority-driven research areas that ACCRI has identified and that need to be pursued to better characterize aviation's impact on climate change.

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Marco A. Giorgetta, Guy P. Brasseur, Erich Roeckner, and Jochem Marotzke
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KRISTA K. LAURSEN, DAVID P. JORGENSEN, GUY P. BRASSEUR, SUSAN L. USTIN, and JAMES R. HUNING

The development of the High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) will make possible a wealth of new geophysical research opportunities in the areas of atmospheric chemistry, climate forcing, weather system structure and evolution, the carbon and water vapor cycles, and ecosystem processes. In this paper, we present a brief background on the history of the HIAPER project and discuss the modifications made to the basic aircraft [a Gulfstream V (GV) business jet] and the infrastructure systems installed to transform it into an environmental research platform. General aircraft performance capabilities that make the GV uniquely suited for high-altitude, long-range studies of geophysical phenomena are also discussed. The conduct of research with HIAPER will require that suitable instrumentation payloads are available for use on the aircraft, and the processes followed by the National Science Foundation (NSF) and the National Center for Atmospheric Research (NCAR) for the development of an initial platform instrumentation suite to meet critical measurements needs are described. HIAPERs unique configuration and capabilities will make it an effective tool for the conduct of weather and water cycle research, the study of atmospheric chemistry and climate forcing, and the monitoring of biosphere structure and productivity, as we shall discuss. We conclude with an overview of the objectives of the initial HIAPER flight-testing program and the process whereby this new research platform will be made available to members of the scientific community for the support of environmental research.

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Cheng Liu, Meng Gao, Qihou Hu, Guy P. Brasseur, and Gregory R. Carmichael

Abstract

Monitoring and modeling/predicting air pollution are crucial to understanding the links between emissions and air pollution levels, to supporting air quality management, and to reducing human exposure. Yet, current monitoring networks and modeling capabilities are unfortunately inadequate to understand the physical and chemical processes above ground, and to support attribution of sources. We highlight the need for the development of an international stereoscopic monitoring strategy that can depict three-dimensional (3D) distribution of atmospheric composition to reduce the uncertainties, and to advance diagnostic understanding and prediction of air pollution. There are three reasons for the implementation of stereoscopic monitoring: (1) current observation networks provide only partial view of air pollution, and this can lead to misleading air quality management actions; (2) satellite retrievals of air pollutants are widely used in air pollution studies, but too often users do not acknowledge that they have large uncertainties, which can be reduced with measurements of vertical profiles; (3) air quality modeling and forecasting require 3D observational constraints. We call on researchers and policymakers to establish stereoscopic monitoring networks and share monitoring data to better characterize the formation of air pollution, optimize air quality management and protect human health. Future directions for advancing monitoring and modeling/predicting air pollution are also discussed.

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Guy P. Brasseur, Martin Schultz, Claire Granier, Marielle Saunois, Thomas Diehl, Michael Botzet, Erich Roeckner, and Stacy Walters

Abstract

A global chemical transport model of the atmosphere [the Model for Ozone and Related Tracers, version 2 (MOZART-2)] driven by prescribed surface emissions and by meteorological fields provided by the ECHAM5/Max Planck Institute Ocean Model (MPI-OM-1) coupled atmosphere–ocean model is used to assess how expected climate changes (2100 versus 2000 periods) should affect the chemical composition of the troposphere. Calculations suggest that ozone changes resulting from climate change only are negative in a large fraction of the troposphere because of enhanced photochemical destruction by water vapor. In the Tropics, increased lightning activity should lead to larger ozone concentrations. The magnitude of the climate-induced ozone changes in the troposphere remains smaller than the changes produced by enhanced anthropogenic emissions when the Special Report on Emission Scenarios (SRES) A2P is adopted to describe the future evolution of these emissions. Predictions depend strongly on future trends in atmospheric methane levels, which are not well established. Changes in the emissions of NOx by bacteria in soils and of nonmethane hydrocarbons by vegetation associated with climate change could have a significant impact on future ozone levels.

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Carlos Nobre, Guy P. Brasseur, Melvyn A. Shapiro, Myanna Lahsen, Gilbert Brunet, Antonio J. Busalacchi, Kathy Hibbard, Sybil Seitzinger, Kevin Noone, and Jean P. Ometto

This paper discusses the development of a prediction system that integrates physical, biogeochemical, and societal processes in a unified Earth system framework. Such development requires collaborations among physical and social scientists, and should include i) the development of global Earth system analysis and prediction models that account for physical, chemical, and biological processes in a coupled atmosphere–ocean–land–ice system; ii) the development of a systematic framework that links the global climate and regionally constrained weather systems and the interactions and associated feedbacks with biogeochemistry, biology, and socioeconomic drivers (e.g., demography, global policy constraints, technological innovations) across scales and disciplines; and iii) the exploration and development of methodologies and models that account for societal drivers (e.g., governance, institutional dynamics) and their impacts and feedbacks on environmental and climate systems.

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Mark P. Baldwin, Thomas Birner, Guy Brasseur, John Burrows, Neal Butchart, Rolando Garcia, Marvin Geller, Lesley Gray, Kevin Hamilton, Nili Harnik, Michaela I. Hegglin, Ulrike Langematz, Alan Robock, Kaoru Sato, and Adam A. Scaife

Abstract

The stratosphere contains ~17% of Earth’s atmospheric mass, but its existence was unknown until 1902. In the following decades our knowledge grew gradually as more observations of the stratosphere were made. In 1913 the ozone layer, which protects life from harmful ultraviolet radiation, was discovered. From ozone and water vapor observations, a first basic idea of a stratospheric general circulation was put forward. Since the 1950s our knowledge of the stratosphere and mesosphere has expanded rapidly, and the importance of this region in the climate system has become clear. With more observations, several new stratospheric phenomena have been discovered: the quasi-biennial oscillation, sudden stratospheric warmings, the Southern Hemisphere ozone hole, and surface weather impacts of stratospheric variability. None of these phenomena were anticipated by theory. Advances in theory have more often than not been prompted by unexplained phenomena seen in new stratospheric observations. From the 1960s onward, the importance of dynamical processes and the coupled stratosphere–troposphere circulation was realized. Since approximately 2000, better representations of the stratosphere—and even the mesosphere—have been included in climate and weather forecasting models. We now know that in order to produce accurate seasonal weather forecasts, and to predict long-term changes in climate and the future evolution of the ozone layer, models with a well-resolved stratosphere with realistic dynamics and chemistry are necessary.

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Gabriele G. Pfister, Sebastian D. Eastham, Avelino F. Arellano, Bernard Aumont, Kelley C. Barsanti, Mary C. Barth, Andrew Conley, Nicholas A. Davis, Louisa K. Emmons, Jerome D. Fast, Arlene M. Fiore, Benjamin Gaubert, Steve Goldhaber, Claire Granier, Georg A. Grell, Marc Guevara, Daven K. Henze, Alma Hodzic, Xiaohong Liu, Daniel R. Marsh, John J. Orlando, John M. C. Plane, Lorenzo M. Polvani, Karen H. Rosenlof, Allison L. Steiner, Daniel J. Jacob, and Guy P. Brasseur

ABSTRACT

To explore the various couplings across space and time and between ecosystems in a consistent manner, atmospheric modeling is moving away from the fractured limited-scale modeling strategy of the past toward a unification of the range of scales inherent in the Earth system. This paper describes the forward-looking Multi-Scale Infrastructure for Chemistry and Aerosols (MUSICA), which is intended to become the next-generation community infrastructure for research involving atmospheric chemistry and aerosols. MUSICA will be developed collaboratively by the National Center for Atmospheric Research (NCAR) and university and government researchers, with the goal of serving the international research and applications communities. The capability of unifying various spatiotemporal scales, coupling to other Earth system components, and process-level modularization will allow advances in both fundamental and applied research in atmospheric composition, air quality, and climate and is also envisioned to become a platform that addresses the needs of policy makers and stakeholders.

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Guy P. Brasseur, Mohan Gupta, Bruce E. Anderson, Sathya Balasubramanian, Steven Barrett, David Duda, Gregg Fleming, Piers M. Forster, Jan Fuglestvedt, Andrew Gettelman, Rangasayi N. Halthore, S. Daniel Jacob, Mark Z. Jacobson, Arezoo Khodayari, Kuo-Nan Liou, Marianne T. Lund, Richard C. Miake-Lye, Patrick Minnis, Seth Olsen, Joyce E. Penner, Ronald Prinn, Ulrich Schumann, Henry B. Selkirk, Andrei Sokolov, Nadine Unger, Philip Wolfe, Hsi-Wu Wong, Donald W. Wuebbles, Bingqi Yi, Ping Yang, and Cheng Zhou

Abstract

Under the Federal Aviation Administration’s (FAA) Aviation Climate Change Research Initiative (ACCRI), non-CO2 climatic impacts of commercial aviation are assessed for current (2006) and for future (2050) baseline and mitigation scenarios. The effects of the non-CO2 aircraft emissions are examined using a number of advanced climate and atmospheric chemistry transport models. Radiative forcing (RF) estimates for individual forcing effects are provided as a range for comparison against those published in the literature. Preliminary results for selected RF components for 2050 scenarios indicate that a 2% increase in fuel efficiency and a decrease in NOx emissions due to advanced aircraft technologies and operational procedures, as well as the introduction of renewable alternative fuels, will significantly decrease future aviation climate impacts. In particular, the use of renewable fuels will further decrease RF associated with sulfate aerosol and black carbon. While this focused ACCRI program effort has yielded significant new knowledge, fundamental uncertainties remain in our understanding of aviation climate impacts. These include several chemical and physical processes associated with NOx–O3–CH4 interactions and the formation of aviation-produced contrails and the effects of aviation soot aerosols on cirrus clouds as well as on deriving a measure of change in temperature from RF for aviation non-CO2 climate impacts—an important metric that informs decision-making.

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Paolo M. Ruti, Oksana Tarasova, Julia H. Keller, Greg Carmichael, Øystein Hov, Sarah C. Jones, Deon Terblanche, Cheryl Anderson-Lefale, Ana P. Barros, Peter Bauer, Véronique Bouchet, Guy Brasseur, Gilbert Brunet, Phil DeCola, Victor Dike, Mariane Diop Kane, Christopher Gan, Kevin R. Gurney, Steven Hamburg, Wilco Hazeleger, Michel Jean, David Johnston, Alastair Lewis, Peter Li, Xudong Liang, Valerio Lucarini, Amanda Lynch, Elena Manaenkova, Nam Jae-Cheol, Satoru Ohtake, Nadia Pinardi, Jan Polcher, Elizabeth Ritchie, Andi Eka Sakya, Celeste Saulo, Amith Singhee, Ardhasena Sopaheluwakan, Andrea Steiner, Alan Thorpe, and Moeka Yamaji

Abstract

Whether on an urban or planetary scale, covering time scales of a few minutes or a few decades, the societal need for more accurate weather, climate, water, and environmental information has led to a more seamless thinking across disciplines and communities. This challenge, at the intersection of scientific research and society’s need, is among the most important scientific and technological challenges of our time. The “Science Summit on Seamless Research for Weather, Climate, Water, and Environment” organized by the World Meteorological Organization (WMO) in 2017, has brought together researchers from a variety of institutions for a cross-disciplinary exchange of knowledge and ideas relating to seamless Earth system science. The outcomes of the Science Summit, and the interactions it sparked, highlight the benefit of a seamless Earth system science approach. Such an approach has the potential to break down artificial barriers that may exist due to different observing systems, models, time and space scales, and compartments of the Earth system. In this context, the main future challenges for research infrastructures have been identified. A value cycle approach has been proposed to guide innovation in seamless Earth system prediction. The engagement of researchers, users, and stakeholders will be crucial for the successful development of a seamless Earth system science that meets the needs of society.

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