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The Overlooked Role of Stratospheric Ozone in forcing Northern Hemispheric climate (TORSO)

Applicant Chiodo Gabriel
Number 180043
Funding scheme Ambizione
Research institution Institut für Atmosphäre und Klima ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Meteorology
Start/End 01.04.2019 - 31.03.2023
Approved amount 920'964.00
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All Disciplines (2)

Discipline
Meteorology
Climatology. Atmospherical Chemistry, Aeronomy

Keywords (6)

Chemistry-Climate interactions; Northern Hemispheric weather and climate; Stratospheric ozone; Greenhouse gases; Ozone depleting substances; Radiative forcing and feedbacks

Lay Summary (German)

Lead
Die Ozonschicht schützt die Erdoberfläche vor schädlicher UV-Strahlung und ermöglicht so das Leben auf der Erde. Störungen in der Ozonschicht können aber auch Klimamuster beeinflussen, wie im Kontext der anthropogenen Ozonzerstörung in der Südhemisphäre belegt wurde. Allerdings bestehen Unsicherheiten bezüglich der Rolle der Ozonschicht in der Nordhemisphäre. Störungen der arktischen Ozonschicht sind mit Klimaschwankungen verbunden. Die Kausalitäten der Wechselwirkung zwischen Ozon und Klima sind jedoch noch ungeklärt und erfordern neue Studien. Insgesamt ist die komplexe Kopplung zwischen Ozon, Strahlung und Dynamik in vielen Klimamodellen nicht berücksichtigt, und trägt zu Unsicherheit in den Prognosen bei.
Lay summary

Inhalt und Ziel des Forschungsprojekts

Das Ziel dieses Projekt ist es, die Rolle der Ozonschicht fürs Wetter und Klima in der Nordhämisphaere zu klären. Erstens werden wir den Effekt der Ozonschicht auf Klimamuster durch Modellsimulationen bestimmen. Zweitens erforschen wir die Wirkung multi-dekadischer Ozontrends auf die Zirkulation. Drittens wollen wir den Einfluss von Ozon-Rückkopplungen auf den Klimaantrieb von Treibhausgasen quantifizieren. Durch verbessertes Prozessverständnis der Ozon-Klima-Rückkoppelungen wird dieses Projekt neue Erkenntnisse zur Bedeutung der Ozonschicht im Erdsystem liefern. Es wird weiterhin den Nutzen einer Berücksichtigung der Ozonchemie für Wetter- und Klimaprognosen klären.

Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts

Dieses Projekt wird zu verbesserten Prognosen in dicht besiedelten Regionen der nördlichen Hemisphäre beitragen. Vorhersagen von arktischem Ozon werden somit auch besser bestimmt. Anhand der Modelldaten wird in Zukunft ein Modell für die Vorhersage der Ozonsäule über Europa zur Verfügung stehen. Das Projekt wird die Grundlagen für die Bewertung politischer Massnahmen im Ozon- und Klimaschutz verbessern, und somit die Anforderung von Ambizione an gesellschaftlich relevante Forschung erfüllen.

Direct link to Lay Summary Last update: 21.03.2019

Responsible applicant and co-applicants

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Abstract

While the influence of stratospheric ozone on tropospheric climate has been extensively assessed in the SouthernHemisphere (SH), large uncertainties remain for its effects on Northern Hemisphere (NH) climate. Arctic ozone exhibitssmall long-term trends, but large inter-annual variability. Ozone has been commonly viewed as a passive constituent thatresponds to stratospheric polar vortex variability. This view has been challenged by recent studies, which suggest thatozone in the NH high latitudes feeds back into the circulation, and plays an active role in surface climate, although thereis still controversy about the direction of causality in the ozone-circulation relationship. This calls for a more rigorousassessment of the impact of ozone on stratosphere-troposphere coupling, and its role in NH climate and seasonalpredictability. Stratospheric ozone influences in the NH may also extend to longer time-scales. Over the 21 st century,Arctic ozone abundances are projected to exceed historical levels. This long-term trend may affect future climateprojections through both dynamical and radiative processes. There is considerable spread in the projections of ozonerecovery, whose dynamical effects on NH surface climate has not been studied so far. Moreover, recent studies havedocumented that the inclusion of interactive ozone chemistry in climate change simulations can reduce (by up to 20%)the projected surface warming: this is largely due to a feedback involving stratospheric water vapor. However, themagnitude of the feedback is model-dependent, and the reason for this uncertainty is unclear. In summary, the impact ofozone variability and trends on the NH climate remains largely unknown, is subject to large uncertainties due to complexcoupling between ozone, circulation and climate, which is not well represented in state-of-the-art climate models.This project aims to answer these questions by combining observational data and a hierarchy of models, offeringan opportunity to assess the role of ozone in NH climate from sub-seasonal to multi-decadal time-scales. First, bycoupling and de-coupling stratospheric ozone chemistry in two climate models, we will assess the influence of ozone onthe Arctic polar vortex variability, stratosphere-troposphere coupling and surface climate, including its influence on thepredictability of the North Atlantic Oscillation (NAO), the dominant mode of climate variability in Europe. Second, wewill quantify the impact of multi-decadal trends in ozone (e.g. Arctic ozone recovery) on the mid-latitude jet in the NorthAtlantic, an important proxy for storminess over Europe, linking the inter-model spread in ozone recovery withuncertainty in NH circulation trends. Third, we will explore the impact of ozone in determining climate sensitivity,through its role as a radiative feedback on climate, and its coupling with stratospheric water vapor.This project will provide novel insights into the role of stratospheric ozone in the Earth system, through aprocess-based understanding of the ozone feedbacks. It will assess the benefit of an accurate representation of ozonechemistry for seasonal to multi-decadal predictions, whilst proposing ways to improve the representation of this couplingin the current generation of models. Thus, it will contribute to narrowing the uncertainty on long-term climateprojections. Output from this project will help guiding future environmental policies, and will thus be valuable fordecision-makers. In this sense, this project will contribute to the Ambizione program's mission to provide impactfulresearch for the benefit of the society.
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