22 Jan 2024
 | 22 Jan 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Understanding the Role of Contrails and Contrail Cirrus in Climate Change: A Global Perspective

Dharmendra Kumar Singh, Swarnali Sanyal, and Donald J. Wuebbles

Abstract. Globally emissions from aviation affect the Earth’s climate via a complex set of processes. Contrail cirrus and carbon dioxide emissions are the largest factors from aviation in the radiative forcing on climate. Although contrail cirrus enhances the impact of natural clouds on the climate, there are still unresolved questions concerning their characteristics and life cycle. Despite extensive research in studying contrails, significant uncertainties persist. Contrail cirrus encompasses linear contrails and the associated cirrus clouds; these are characterized by ice particle properties, e.g., size, concentration, extinction, ice water content, optical depth, geometrical depth, and cloud coverage. The climate impact of contrails may intensify due to projected increases in air traffic. The radiative forcing from global contrail cirrus has the potential to triple and could reach as much as 160 mW m−2 by 2050. This projection is based on anticipated growth in air traffic and a potential shift to higher altitudes. The future climate impact of contrail cirrus is influenced by factors like the magnitude and geographical spread in air traffic, advancements in fuel efficiency, the effects from use of alternative fuels, and the effects of the changing climate on the background atmosphere. This study reviews the microphysical processes affecting contrail formation and the aging of contrails and contrail-cirrus. Furthermore, the study explores global observational datasets for contrails, current analyses, and future projections and will aid in evaluating the effectiveness and trade-offs associated with various mitigation strategies. The research highlights gaps in knowledge and uncertainties while outlining research priorities for the future.

Dharmendra Kumar Singh, Swarnali Sanyal, and Donald J. Wuebbles

Status: open (until 30 Mar 2024)

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Dharmendra Kumar Singh, Swarnali Sanyal, and Donald J. Wuebbles
Dharmendra Kumar Singh, Swarnali Sanyal, and Donald J. Wuebbles


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Short summary
Radiative forcing of contrails could triple by 2050 due to increased air traffic and potential changes in flight altitudes. Factors like air traffic patterns, fuel efficiency, alternative fuels, and climate change further influence this impact. By highlighting gaps in knowledge and uncertainties, the research helps set priorities for future studies and assess strategies to mitigate the environmental impact of aviation emissions.