WP1 - Atmosphere processes

This work package (WP) will improve the representation of atmospheric composition (aerosols and trace gases) in the project ESMs. An emphasis will be on advancing the degree of interaction between atmospheric chemistry, aerosol, cloud and radiation parts of the models. We will also develop the emission of trace gases and aerosol species from the marine and terrestrial biosphere. A key aim of the work package is to assess the impact of these  model developments on historical radiative forcing and future climate feedbacks.

Our two main objectives are (i) improving the description of trace gas and aerosol species, aerosol-radiation, and aerosol-cloud interactions in the atmospheric component of the project ESMs; and ii) quantifying the impact of the parameterization improvements and process couplings on the Effective Radiative Forcing (ERF) and climate sensitivity of the ESMs.

Institutions involved: Météo-France, UK Met Office, University of Leeds, the UK National Centre for Atmospheric Sciences, Norwegian Meteorological Institute and the Institute Pierre-Simon Laplace will all contribute to this WP via development and evaluation of atmospheric improvements within their own models. SMHI will assist in porting relevant evaluation diagnostics into ESMValTool.

WP Leaders

Jane Mulcahy

Jane Mulcahy

UKESM Science Manager,
Met Office Hadley Centre - Exeter (UK)

I am the Science Manager within the UKESM project overseeing the scientific model development and evaluation of the UKESM model within the joint NERC-Met Office UKESM team along with the contributions from the wider UK academic and international partners. I have over 15 years of experience in atmospheric aerosol research and over 12 years of experience in model development and evaluation of atmospheric aerosols and their interactions across a range of time and spatial scales from high resolution numerical weather prediction to fully coupled Earth System models. I sit on the science management board of the United Kingdom Chemistry and Aerosol (UKCA) project and have previously led the implementation of the GLOMAP-mode aerosol scheme in the Global Atmosphere 7.0 (GA7) configuration of the Met Office Unified Model for use in HadGEM3 physical climate and UKESM1 simulations for CMIP6. I have particular research interests in improving the representation of aerosol-cloud interactions in models and understanding aerosol-climate feedbacks within the full Earth system. I have authored/co-authored over 25 peer-reviewed publications.

In ESM2025

I co-lead WP1 with Pierre Nabat, which aims to improve atmospheric processes in the project ESMs. I will also work within this WP on improving the interactive marine emissions within the UKESM mode.

Pierre Nabat

Pierre Nabat

Research scientist,
Météo-France-CNRM - Toulouse (France)

I am a researcher at Météo-France/CNRM, specialized in aerosol modelling and the study of aerosol-climate interactions. I am involved in the development of the global (CNRM-ESM) and regional (CNRM-RCSM) climate models of CNRM, with a focus on the aerosol module. I have contributed to international initiatives such as CMIP6/AerChemMIP and CORDEX, as well as to international projects such as CRESCENDO and CONSTRAIN. I am author or co-author of about 40 peer-reviewed articles, and have received the MedCLIVAR Young Scientist Award in 2018.

In ESM2025

In ESM2025 I co-lead WP1 with Jane Mulcahy, which focuses on atmospheric processes, namely chemistry-aerosol-climate interactions. I will also contribute to improvements in CNRM-ESM, as far as aerosols and chemistry are concerned.

Milestones & Delievrables

Project start


MS1.1 – Month 6

Definition of key diagnostics to evaluate planned ESM improvements at the process level (CT1/WP1/atmosphere) and with respect to coupled interactions and coupled performance (CT2). Identification of key observational data sets and initial scoping of diagnostics intended for ESMValtool.

MS1.2  Month 18

Preliminary versions of new/improved atmospheric parameterization schemes passed to CT2 for coupling and initial testing.

MS1.3 – Month 24

Atmosphere-only (AMIP, AMIP+4K, ERF and AMIP perturbation) simulations for evaluation of new parameterizations of gas-phase chemistry and aerosol-radiation-cloud developments made available to XCA1 and to WP11 and WP12 for constraining parameters in OS-MAGICC.

MS1.4 – Month 27 Updated versions of new/improved atmospheric parameterization schemes passed to CT2 for final coupling, tuning and use in XCA2 coupled simulations.

D1.1 – Jan 2024

Report on the implementation and evaluation of interactive tropospheric chemistry and its coupling with aerosols.

D1.2  – May 2024

Report on the implementation and evaluation of new or improved aerosol-radiation and aerosol-cloud interactions in participating ESMs.  






Project end