The Hadgem2-ES Implementation of CMIP5 Centennial Simulations
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Geosci. Model Dev., 4, 543–570, 2011 www.geosci-model-dev.net/4/543/2011/ Geoscientific doi:10.5194/gmd-4-543-2011 Model Development © Author(s) 2011. CC Attribution 3.0 License. The HadGEM2-ES implementation of CMIP5 centennial simulations C. D. Jones1, J. K. Hughes1, N. Bellouin1, S. C. Hardiman1, G. S. Jones1, J. Knight1, S. Liddicoat1, F. M. O’Connor1, R. J. Andres2, C. Bell3,†, K.-O. Boo4, A. Bozzo5, N. Butchart1, P. Cadule6, K. D. Corbin7,*, M. Doutriaux-Boucher1, P. Friedlingstein8, J. Gornall1, L. Gray9, P. R. Halloran1, G. Hurtt10,16, W. J. Ingram1,11, J.-F. Lamarque12, R. M. Law7, M. Meinshausen13, S. Osprey9, E. J. Palin1, L. Parsons Chini10, T. Raddatz14, M. G. Sanderson1, A. A. Sellar1, A. Schurer5, P. Valdes15, N. Wood1, S. Woodward1, M. Yoshioka15, and M. Zerroukat1 1Met Office Hadley Centre, Exeter, EX1 3PB, UK 2Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6335, USA 3Meteorology Dept, University of Reading, Reading, RG6 6BB, UK 4National Institute of Meteorological Research, Korea Meteorological Administration, Korea 5School of GeoSciences, University of Edinburgh, The King’s Buildings, Edinburgh EH9 3JW, UK 6Institut Pierre-Simon Laplace, Universite´ Pierre et Marie Curie Paris VI, 4 Place de Jussieu, case 101, 75252 cedex 05 Paris, France 7Centre for Australian Weather and Climate Research, CSIRO Marine and Atmospheric Research, Aspendale, Victoria, Australia 8College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, EX4 4QF, UK 9National Centre for Atmospheric Science, Department of Physics, University of Oxford, Oxford, OX1 3PU, UK 10Department of Geography, University of Maryland, College Park, MD 21403, USA 11Department of Physics, University of Oxford, Oxford, OX1 3PU, UK 12Atmospheric Chemistry Division, UCAR, Boulder, USA 13Earth System Analysis, Potsdam Institute for Climate Impact Research, Germany 14Max Planck Institute for Meteorology, Hamburg, Germany 15School of Geographical Sciences, University of Bristol, Bristol BS81SS, UK 16Pacific Northwest National Laboratory, Joint Global Change Research Institute, University of Maryland, College Park, MD 20740, USA *now at: Colorado State University, Fort Collins, USA †deceased, 20 June 2010 Received: 7 March 2011 – Published in Geosci. Model Dev. Discuss.: 31 March 2011 Revised: 14 June 2011 – Accepted: 19 June 2011 – Published: 1 July 2011 Abstract. The scientific understanding of the Earth’s cli- the Met Office Hadley Centre ESM, HadGEM2-ES for the mate system, including the central question of how the cli- CMIP5 set of centennial experiments. We document the pre- mate system is likely to respond to human-induced pertur- scribed greenhouse gas concentrations, aerosol precursors, bations, is comprehensively captured in GCMs and Earth stratospheric and tropospheric ozone assumptions, as well as System Models (ESM). Diagnosing the simulated climate re- implementation of land-use change and natural forcings for sponse, and comparing responses across different models, is the HadGEM2-ES historical and future experiments follow- crucially dependent on transparent assumptions of how the ing the Representative Concentration Pathways. In addition, GCM/ESM has been driven – especially because the im- we provide details of how HadGEM2-ES ensemble members plementation can involve subjective decisions and may dif- were initialised from the control run and how the palaeo- fer between modelling groups performing the same experi- climate and AMIP experiments, as well as the “emission- ment. This paper outlines the climate forcings and setup of driven” RCP experiments were performed. Correspondence to: C. D. Jones (chris.d.jones@metoffice.gov.uk) Published by Copernicus Publications on behalf of the European Geosciences Union. 544 C. D. Jones et al.: The HadGEM2-ES implementation of CMIP5 centennial simulations 1 Introduction In the following, we briefly describe HadGEM2-ES ESM, which is documented in detail in Collins et al. (2011). Phase 5 of the Coupled Model Intercomparison HadGEM2-ES is a coupled AOGCM with atmospheric reso- Project (CMIP5) is a standard experimental protocol lution of N96 (1.875◦ × 1.25◦) with 38 vertical levels and an for studying the output of coupled ocean-atmosphere general ocean resolution of 1◦ (increasing to 1/3◦ at the equator) and circulation models (GCMs). It provides a community-based 40 vertical levels. HadGEM2-ES also represents interactive infrastructure in support of climate model diagnosis, val- land and ocean carbon cycles and dynamic vegetation with an idation, intercomparison, documentation and data access. option to prescribe either atmospheric CO2 concentrations or The purpose of these experiments is to address outstanding to prescribe anthropogenic CO2 emissions and simulate CO2 scientific questions that arose as part of the IPCC Fourth concentrations as described in Sect. 2. An interactive tropo- Assessment report (AR4) process, improve understanding spheric chemistry scheme is also included, which simulates of climate, and to provide estimates of future climate the evolution of atmospheric composition and interactions change that will be useful to those considering its possible with atmospheric aerosols. The model timestep is 30 min consequences and the effect of mitigation strategies. (atmosphere and land) and 1 h (ocean). Extensive diagnos- CMIP5 began in 2009 and is meant to provide a frame- tic output is being made available to the CMIP5 multi-model work for coordinated climate change experiments over a five archive. Output is available either at certain prescribed fre- year period and includes simulations for assessment in the quencies or as time-average values over certain periods as IPCC Fifth Assessment Report (AR5) as well as others that detailed in the CMIP5 output guidelines (see URL 2 in Ap- extend beyond the AR5. The IPCC’s AR5 is scheduled to be pendix A). published in September 2013. CMIP5 promotes a standard The CMIP5 simulations include 4 future scenarios re- set of model simulations in order to: ferred to as “Representative Concentration Pathways” or RCPs (Moss et al., 2010). These future scenarios have – evaluate how realistic the models are in simulating the been generated by four integrated assessment models (IAMs) recent past, and selected from over 300 published scenarios of future – provide projections of future climate change on two greenhouse gas emissions resulting from socio-economic time scales, near term (out to about 2035) and long term and energy-system modelling. These RCPs are labelled ac- (out to 2100 and beyond), and cording to the approximate global radiative forcing level in 2100 for RCP8.5 (Riahi et al., 2007), during stabilisation af- – understand some of the factors responsible for differ- ter 2150 for RCP4.5 (Clarke et al., 2007; Smith and Wigley, ences in model projections, including quantifying some 2006) and RCP6 (Fujino et al., 2006) or the point of maxi- key feedbacks such as those involving clouds and the mal forcing levels in the case RCP3-PD (van Vuuren et al., carbon cycle. 2006, 2007), with PD standing for “Peak and Decline”. The latter scenario has previously been known as RCP2.6, as ra- A much more detailed description can be found on the diative forcing levels decline towards 2.6 Wm−2 by 2100. CMIP5 project webpages (see URL 1 in Appendix A) and Note that these radiative forcing levels are illustrative only, in Taylor et al. (2009). because greenhouse gas concentrations, aerosol and tropo- There are a number of new types of experiments proposed spheric ozone precursors are prescribed, resulting in a wide for CMIP5 in comparison with previous incarnations. As in spread in radiative forcings across different models. previous intercomparison exercises, the main focus and effort The experimental protocol involves performing a histori- rests on the longer time-scale (“centennial”) experiments, cal simulation (defined for HadGEM2-ES as 1860 to 2005) including now emission-driven runs of models that include using the historical record of climate forcing factors such as a coupled carbon-cycle (ESMs). These centennial experi- greenhouse gases, aerosols and natural forcings such as solar ments are being performed at the Met Office Hadley Centre and volcanic changes. The model state at 2005 is then used with the HadGEM2-ES Earth System model (Collins et al., as the initial condition for the 4 future RCP simulations. Fur- 2011; Martin et al., 2011); a configuration of the Met Of- ther extension of the RCP simulations to 2300 is also imple- fice’s Unified Model. Figure 1 outlines the main experiments mented as detailed in the RCP White Paper (see URL 3 in and groups them into categories. The inner circle denotes Appendix A) and Meinshausen et al. (2011). “core” priority experiments with tier 1 (middle circle) and Many of these experiments require technical implementa- tier 2 (outer circle) having successively lower priority. Ex- tion by means of either or both of the following: periments are split between climate projections (blue), ide- alised experiments aimed at elucidating process understand- – time-varying boundary conditions such as concentra- ing in the models (yellow), model evaluation, including pre- tions of greenhouse gases or emissions of reactive industrial control runs and historical experiments (red), and chemical species or aerosol pre-cursors. These may be additional experiments for models with a coupled carbon cy- given as single, global-mean numbers, or supplied as cle (green). 2-D or 3-D fields of data, Geosci. Model Dev., 4, 543–570, 2011 www.geosci-model-dev.net/4/543/2011/ C. D. Jones et al.: The HadGEM2-ES implementation of CMIP5 centennial simulations 545 Proje mate ctio Cli ns -PD & EC ECP3 P8.5 e M cl y t c s o n te 6 o ck RCP b a & EC d r b D P Uniform SST a d -P 4 e C e 3 .5 e l e P c f RC l RCP8.5 RCP4.5 E-Driven & U y g 2 in O c f RCP 8 e . C C r 5 . n s C e i % o l a f e l a o 1 r l d tr e d a b n d n b I u o o n a C e n d l iv e i c a r O 2 o i k C d v r i t - r y t s d e b c u n s n d o l s i I 2 t e n r t i s Fixed SST 4xC - s t i p e O r u m g a a r P C E n i .