Creating a comprehensive model to support greenhouse gas emission strategies: A case-study for Ireland

Climate change mitigation policies should be supported by a scientific infrastructure that includes inventories, models and observations; this infrastructure could provide an independent assessment of greenhouse gas (GHG) emissions and contribute to the formulation of effective policies at national and regional scale. However, current policies are largely based on sectoral inventories that use land-use and land-cover information to estimate GHG emissions. Other parts of the infrastructure are not well developed at national scales. Observations of GHG concentrations and fluxes are relatively few and not designed to assess net emissions from complex landscapes (e.g. rural landscapes, with diverse natural and anthropogenic sources and sinks). Moreover, land-surface models are rarely employed at these scales to assess the inventory in the context of observations. In this paper we outline the development of this infrastructure for the island of Ireland. We apply an enhanced version of the Weather and Research Forecasting model (WRF-chem); this model simulates the atmospheric mixing of GHGs based on anthropogenic emissions and biogenic net contributions over natural, rural and urban land cover types. Model results for selected winter and summer periods are evaluated against meteorological observations and measurements of CO2 concentrations and Net Ecosystem Exchange (NEE), derived from available flux and atmospheric monitoring sites. While anthropogenic emissions of Carbon Dioxide dominate over urban areas, emissions of Methane are linked to grasslands and dairy farming, with forests and peatlands acting as either sources/sinks depending on season and weather. This model framework provides a tool for identifying the profile of net GHG emissions at national and local scales and the development and evaluation of place-based mitigation policies.