SHIVA focuses on four major objectives, i.e. investigations
- of the oceanic emission strengths of a suite of halogenated source gases: Here emphasis is put on the production, emission and transport of ODS. Inter-dependencies derived from our own field observations as well as surveys of ongoing work in this area will help establish potential climate sensitivities of VSLS emissions.
- of the atmospheric transport and chemical transformation of halogenated VSLS and their PGs during their journey from the surface to the TTL and finally into the stratosphere. Her a combination of aircraft and balloon observations together with process-oriented meso-scale modeling is used. These investigations are corroborated by space-based remote sensing of marine phytoplankton biomass as a possible proxy for the ocean-atmosphere flux of VSLS.
- of the past, present and likely future trend of the total halogen burden in the stratosphere, which is established from the systematic VSLS emission inventory established under theme 1 and 2. Here the impact of climate-sensitive feedbacks between transport and the delivery of ODS to the stratosphere, and their lifetime within it, is studied using tracer observations and modeling. When all this knowledge is combined, the assessed climate sensitivities will eventually support the construction of future-climate scenarios of VSLS emissions and possible pathways for their delivery to the stratosphere.
- on the impact of long and short-lived halogenated SGs and their inorganic PGs on past, present and future ozone is assessed for the upper troposphere, TTL and global stratosphere. Here global modeling includes the contribution of all ODS, including VSLS (which have hitherto normally been excluded from such models) to past, present and future ozone loss. The sensitivity of natural ODS emissions to climate change parameters investigated under theme 3 is 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 and to better predict the rate, timing and climate-sensitivity of ozone-layer recovery.