HadCM3 stands for Hadley Center Coupling model version three. This global climate model (GCM) was developed by the Met Office Hadley Center for Climate Science and Services in 2000, and was used as one of the major GCM ever since, starting from the Third Assessment Report by the Intergovernmental Panel on Climate Change in 2001. The model includes two elements – HadAm3 (for atmospheric modeling) and HadOM3 (for oceanic modeling), therefore forming a coupling assessment model. The GCM was a further development of the previous model HadCM2, also developed at Hadley (Bloom, 184).
Model description
The model includes 2 elements for the simulation of the world climate – atmospheric and oceanic. It also includes elements of modeling for sea ice, land surface and vegetation. Additional algorithms allow to model changes in atmospheric chemistry including massive aerosols and indirect effects. The model does not include elements of interactive biogeochemistry, dynamic vegetation and ice-sheets.
There are the following groups of variables necessary for calculation of the model depending on the particular field (Johns et al., 62):
For atmosphere – temperature, ultraviolet velocity, surface pressure, liquid water content and potential temperature, cloud fraction, SO2 and DMS concentration;
For the ocean – temperature, salinity, baroclinic velocity, mixed-layer depth;
For sea ice – sea-ice fraction, thickness and snow depth;
For the surface – water fluxes, terrain albedo, canopy conductance.
There are also variables that are passed between components of the model (Ibid.):
Atmosphere to ocean – wind stress, penetrative solar radiation, net heat flux, the positive difference between precipitation and evaporation, snowfall, river outflow, sublimation and ice melting; ocean to atmosphere – surface circulation, ice depth and concentration, depth of snow, sea surface temperature.
Atmosphere – land – fluxes (heat, moisture and momentum), surface and air temperature, humidity, snow fraction.
Sea ice – ocean – heat fluxes, top and bottom ice melt, temperature, snow and ice fraction and thickness.
The model is usually used as a combination of atmospheric and oceanic sub-models for purpose of both historic assessment and futuristic forecasts, with the simulation length of up to one thousand years. The model is not specific to a certain region and may be applied at a global scale.
The model is unique in several ways. First, despite a potentially global scope, it also offers a relatively high resolution. HadCM3 has the resolution of 3.75 to 2.5 degrees, and the HadOM3 has even higher precision – 1.25 to 1.25 degrees. In the former case, it corresponds to the distance of 300 km between points, while in the latter – only 70-75 km (Turner et al., 107). The system works for long periods of time and involves a wide range of variables required for the calculation. It does not only consider natural processes, but also an anthropogenic factor, including but not limited to changes in surface vegetation and atmospheric pollution.
Speaking of the compliance of the model results with the charts in the textbook, the model resulted from several runs of HadCM3 provided results on the CO2 emissions identical to Chart 4.14 (both in terms of possible scenarios and range of values) and Chart 4.30 – the range of average annual temperatures from 1860 to 2020 (HadCM3 normally runs from 1859, but this difference is negligible). Modelling of the impact of particular chemical compounds in the atmosphere does not comply to the charts in the textbook, as HarCM3 model has very limited scope regarding air chemistry.
Comparative analysis of HadCM3 (Randall et al., 82)
Conclusion
Hadley Center Coupling model version three is a well-established and widely used climate model with extensive application within the framework of IPCC Global Assessment Reports. The two components of the model may be used either separately or together to provide a comprehensive global or regional model of climate processes and change in two or three dimensional forms. The precision of the system and high resolution are comparable to or even exceed other existing systems. While other models may be more often used by the governmental institutions of particular nations, HadCM3 remains popular for the international research requiring a thorough computation of numerous variables and their impact on climatic change. Despite certain technical inaccuracies, it may assess data for a thousand-year period, which is a benchmark unreachable for other models. The model may be used either alone or in combination with other prediction and evaluation tools to provide an accurate and comprehensive picture of the climate change and respective anthropogenic impact.
Reference
Bloom, Arnold J (2010) Global Climate Change, Convergence of Disciplines, Sinauer Associates, Inc, Sunderland, Massachusetts.
Randall, D.A., R.A. Wood, S. Bony, R. Colman, T. Fichefet, J. Fyfe, V. Kattsov, A. Pitman, J. Shukla, J. Srinivasan, R.J. Stouffer, A. Sumi and K.E. Taylor, (2007): Cilmate Models and Their Evaluation. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA
Johns, T. C., et al. "Anthropogenic climate change for 1860 to 2100 simulated with the HadCM3 model under updated emissions scenarios." Climate Dynamics 20.6 (2003): 583-612.
Turner, J., et al. "The performance of the Hadley Centre Climate Model (HadCM3) in high southern latitudes." International journal of climatology 26.1 (2006): 91-112.
