HadGEM

HadGEM
Name	HadGEM
Developer	Met Office
First release	2006
Latest release	2011
Programming language	Fortran
Platform	High-performance computing
License	Proprietary

HadGEM

HadGEM is a family of coupled atmosphere–ocean general circulation models developed by the Met Office’s UK Centre for Atmospheric Science and Met Office Hadley Centre. The suite was designed to advance climate projection capability following earlier frameworks used for the IPCC Fourth Assessment Report and contributes to experiments coordinated by the Coupled Model Intercomparison Project and the World Climate Research Programme. Leading applications include attribution studies, regional downscaling for agencies such as the European Centre for Medium-Range Weather Forecasts and impact assessments for the United Nations Framework Convention on Climate Change.

Overview

HadGEM models integrate components representing the atmosphere, ocean, land surface, and sea ice to simulate physical processes relevant to climate. Development built on lineage from the HadCM3 and the Unified Model systems used in operational forecasting at the Met Office. HadGEM variants were employed in large international assessments including contributions to the IPCC reports and multi-model ensembles run by the World Climate Research Programme's Working Group on Coupled Modelling. Collaborative links extended to research institutes such as the National Oceanography Centre, the British Antarctic Survey, and universities including University of Oxford and University of Cambridge.

Development and Versions

Initial publicized configurations emerged in the mid-2000s and evolved through named releases such as HadGEM1 and HadGEM2, with incremental tuning and structural changes reflecting advances in parameterization and resolution. Development teams included scientists from the Met Office Hadley Centre and partner groups at the National Centre for Atmospheric Science and the Natural Environment Research Council. Model intercomparison projects like CMIP5 and CMIP3 provided benchmarks, while projects such as the PRUDENCE and ENSEMBLES regional efforts informed downscaling. Funding and programmatic support came from entities including the UK Department for Environment, Food and Rural Affairs and the European Commission research directorates.

Model Components and Configuration

Atmospheric dynamics and physics in HadGEM were implemented using the Unified Model dynamical core, coupling to an ocean component derived from the NEMO family and an ice model influenced by the CICE architecture. Land surface processes used schemes linked to the Joint UK Land Environment Simulator and vegetation descriptions influenced by databases such as MODIS observational products. The coupled system employed exchange interfaces consistent with the Earth System Modeling Framework conventions used by centers like NASA Goddard Institute for Space Studies and the Geophysical Fluid Dynamics Laboratory. Configurable resolution options ranged from global grids suited to century-scale projections to higher-resolution nested setups for regional studies undertaken in collaboration with the Met Office’s forecasting groups.

Performance and Evaluation

Validation work compared HadGEM output with observational records from platforms and programs such as ARGO, Satellite Active Cavity Radiometer Irradiance Monitor, and the Global Precipitation Climatology Project. Benchmarking versus contemporaneous models from NOAA, NASA, ECMWF, and research centers in Japan and Germany examined fidelity in simulating modes like the El Niño–Southern Oscillation, the North Atlantic Oscillation, and the Indian Ocean Dipole. Evaluation papers appeared in journals associated with publishers like Nature Publishing Group and American Geophysical Union outlets, addressing biases in mean state, variability, and teleconnections. Performance metrics informed tuning for energy balance, water cycle closure, and the representation of extreme events referenced in assessments by the Intergovernmental Panel on Climate Change.

Applications and Use Cases

HadGEM outputs supported impact assessments for sectors influenced by climate variability and change, informing adaptation planning for bodies such as the European Environment Agency, Department of Energy and Climate Change (UK), and regional authorities. Research utilizing HadGEM examined sea level contributions relevant to studies by the Intergovernmental Panel on Climate Change and cryosphere interactions with investigations by the British Antarctic Survey and the Scott Polar Research Institute. The model underpinned downscaling exercises used by urban planners and infrastructure groups in collaboration with institutions like the Royal Society and academic groups at the University of Leeds and University of Exeter. Ensemble experiments using HadGEM informed attribution analyses cited in reports by the World Meteorological Organization and national climate assessments.

Limitations and Criticisms

Critiques highlighted persistent biases common to coupled models of the era, such as systematic errors in tropical precipitation, sea surface temperature drifts, and representation of cloud feedbacks noted in assessments by the IPCC. Computational expense constrained ensemble sizes compared with models run at lower resolution by agencies like NOAA and research centers in China and India, affecting probabilistic inference for extremes. Some studies pointed to structural sensitivities tied to parameter choices in convection and ocean mixing schemes examined alongside work at Scripps Institution of Oceanography and Lamont–Doherty Earth Observatory. Ongoing community efforts, coordinated through forums such as the World Climate Research Programme and collaborations with the European Centre for Medium-Range Weather Forecasts, addressed these limitations through model intercomparison, increased resolution, and coupling of biogeochemical modules.

Category:Climate models