Emissions of anthropogenic aerosol and precursor compounds substantially alter the Earth’s radiative balance, change the oxidation capacity of the atmosphere, alter cloud processes and precipitation amounts, and result in significant impacts on human health and ecosystems. One of the primary tools used to examine these effects are global models. There are a number of characteristics of emissions that can influence model results, such as seasonality and assumed injection height, that are not either uncertain or not specified in current global datasets.

The aim of Emissions-MIP is to quantify the influence of these characteristics on model results. The project has two phases. In Phase 1, atmosphere-only simulations will be used to examine a impact of a suite of emission perturbations. The results from Phase I will be evaluated to select a small set of perturbations to examine using ensembles of coupled model simulations in  Phase 2.

Currently participating models/modeling groups include: PNNL (E3SM), PNNL (CESM1), GSFC (GEOS), GISS, GFDL, NCAR, HadGEM-UKCA, OsloCTM3, MIROC-SPRINTARS, NorESM.

Current Status (June 2021):

The Phase 1 experiments use atmosphere-only model runs with specified ocean temperatures and nudged winds run for six year period, reporting concentration, deposition, and forcing variables. While these runs do not include fully coupled dynamics, these are computationally less expensive and we can, therefore, quantify the magnitude of any effects for a larger number of perturbations. We can also more directly compare results from both ESMs and CTMs in the Phase 1 experiments.

Phase 1a

The experimental protocol for Phase 1a was developed fall 2020. The reference case uses CMIP6 historical emissions. The current experimental protocol is available here.

The following five perturbation cases were identified for Phase 1a:

As of June 2021, eight models have completed these simulations and two are partially completed. A version of the CMIP6 emissions data with no seasonality for use in these experiments are available at the Emissions-MIP data repository.

Phase 1b

Phase 1b simulations will focus on uncertainties in the spatial distribution of ocean shipping emissions. The experimental protocol is now being tested and will be released once it is finalized.

This project is using the ESMVal tool for analyzing model results. We would like to thank the ESMValtool team for technical assistance.

More modeling groups are invited to join the project. Please contact ssmith@pnnl.gov for further information.