SHIVA

Stratospheric ozone: Halogen Impacts in a Varying Atmosphere

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 Obiettivo del progetto (Objective)

'SHIVA aims to reduce uncertainties in present and future stratospheric halogen loading and ozone depletion resulting from climate feedbacks between emissions and transport of ozone depleting substances (ODS). Of particular relevance will be studies of short and very short-lived substances (VSLS) with climate-sensitive natural emissions. We will perform field studies of ODS production, emission and transport in understudied, but critical, regions of the tropics using ship, aircraft and ground-based instrumentation. We will parameterise potential climate sensitivities of emissions based on inter-dependencies derived from our own field studies, and surveys of ongoing work in this area. We will study the chemical transformation of ODS during transport from the surface to the tropical tropopause layer (TTL), and in the stratosphere, using a combination of aircraft and balloon observations together with process-oriented meso-scale modelling. These investigations will be corroborated by space-based remote sensing of marine phytoplankton biomass as a possible proxy for the ocean-atmosphere flux of ODS. From this a systematic emission inventory of VSLS ODS will be established to allow construction of future-climate scenarios. The impact of climate-sensitive feedbacks between transport and the delivery of ODS to the stratosphere, and their lifetime within it, will be studied using tracer observations and modelling. Further global modelling will assess the contribution of all ODS, including VSLS (which have hitherto normally been excluded from such models) to past, present and future ozone loss. Here, the sensitivity of natural ODS emissions to climate change parameters will be used in combination with standard IPCC climate model scenarios in order to drive measurement-calibrated chemical transport model (CTM) simulations for present and future stratospheric ozone; to better predict the rate, timing and climate-sensitivity of ozone-layer recovery.'

Introduzione (Teaser)

Scientists are now better able to predict the effect of climate change on the Earth's ozone layer. An EU-funded project has investigated the impact of naturally emitted substances containing halogens.

Descrizione progetto (Article)

Halogens (e.g. chlorine, bromine and iodine) have contributed to the decline of the global ozone layer, which absorbs most of the Sun's ultraviolet radiation. The Montreal Protocol (1987) was responsible for phasing out the production of various ozone-depleting substances (ODSs) such as halogenated hydrocarbons.

Naturally emitted medium short-lived substances (MSLSs) and very short-lived substances (VSLSs) containing bromine and iodine can enter the stratosphere. Here, in the second major layer of Earth's atmosphere, they are broken down by sunlight to release ozone destroying halogens.

The 'Stratospheric ozone: Halogen impacts in a varying atmosphere' (http://shiva.iup.uni-heidelberg.de/ (SHIVA)) initiative aimed to increase understanding of the role of VSLSs. This will ensure that predictions of the future state of the global stratospheric ozone can be made with greater certainty for a changing climate. Determining the uncertain contribution of MSLSs and VSLSs to the production of ozone-depleting halogens is challenging due to their sensitivity to climate changes.

Sources of VSLSs include marine plants known as phytoplankton, as well as non-living chemical and physical processes that occur near the surface of the oceans. VSLS emissions from natural or cultivated seaweed are also potentially important, particularly in tropical regions of the world.

Tropical weather is warm and helps to carry ODSs into the stratosphere, thus contributing to ozone loss. The consortium therefore conducted long-term measurements in conjunction with Malaysian research partners in the South China Sea and along the coastline of the Malaysian Peninsula and Borneo.

Air measurements were taken from land, ships, aircraft, balloons and satellites and combined with computer models. Data from the SHIVA initiative will reduce uncertainty in predicting climate changes and ozone recovery or losses. In addition, the project will increase understanding of the future oxidation capacity of the lower atmosphere, as well as the composition and dynamics of the overlaying stratosphere.

The work conducted by the SHIVA consortium contributed to the scientific basis of the United Nations (UN) Montreal Protocol on Substances that Deplete the Ozone Layer, the UN Convention on Climate Change and global climate change research.