Global sensitivity analysis of chemistry & climate model budgets of tropospheric ozone and OH: exploring model diversity

For the first time, we apply Gaussian process emulation with three independent global chemistry-transport models to quantify the sensitivity of ozone and hydroxyl radicals (OH) to important climate-relevant variables, poorly characterised processes and uncertain emissions. We show a clear sensitivity of tropospheric ozone to atmospheric humidity and precursor emissions which is similar for the models, but find large differences between models for methane lifetime, highlighting substantial differences in the sensitivity of OH to primary and secondary production.

This approach al-lows us to identify key areas where model improvements are required while providing valuable new insight into the processes driving tropospheric composition change.