Improving the ability of coupled chemistry-climate models to project future changes in polar stratospheric ozone and its influence on surface climate in the polar regions

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The primary objective of the intended research is to reduce uncertainty in projections of polar ozone changes to 2100 and their influence on surface climate in the polar regions. The first step towards achieving this goal will be to apply recently developed diagnostic tools to assess the ability of state-of-the-art coupled chemistry-climate models to capture key sensitivities characterising the stratospheric processes leading to ozone depletion. These tools consist of semi-empirical equations that are fitted to chemistry-climate model output. The first diagnostic tracks the sensitivity of chlorine activation to polar stratospheric temperatures and chlorine loading and thereby establishes a connection between greenhouse gas induced changes in polar stratospheric temperatures and ozone depletion. The second semi-empirical equation tracks the sensitivity of the rate of change of ozone to chlorine activation obtained from the first equation. The fit coefficients from these equations will be compared with those obtained from application of the diagnostic tools to real world observations thus establishing performance benchmarks for the chemistry-climate models. These activities will take place within the international Chemistry-Climate Model Validation Activity of SPARC (Stratospheric Processes And their Role in Climate), a core project of the World Climate Research Programme. The second step towards achieving the proposal objectives will be diagnosis of the improved projections of polar ozone changes in terms of their contribution to radiative forcing of surface climate in the polar regions.