The HadGEM2 family of Met Office Unified Model climate configurations

Abstract

Abstract. We describe the HadGEM2 family of climate configurations of the Met Office Unified Model, MetUM. The concept of a model "family" comprises a range of specific model configurations incorporating different levels of complexity but with a common physical framework. The HadGEM2 family of configurations includes atmosphere and ocean components, with and without a vertical extension to include a well-resolved stratosphere, and an Earth-System (ES) component which includes dynamic vegetation, ocean biology and atmospheric chemistry. The HadGEM2 physical model includes improvements designed to address specific systematic errors encountered in the previous climate configuration, HadGEM1, namely Northern Hemisphere continental temperature biases and tropical sea surface temperature biases and poor variability. Targeting these biases was crucial in order that the ES configuration could represent important biogeochemical climate feedbacks. Detailed descriptions and evaluations of particular HadGEM2 family memCorrespondence to: G. M. Martin (gill.martin@metoffice.gov.uk) bers are included in a number of other publications, and the discussion here is limited to a summary of the overall performance using a set of model metrics which compare the way in which the various configurations simulate present-day climate and its variability.

Sensitivity of an Earth system climate model to idealized radiative forcing

“…HadGEM2-AO includes atmospheric, land surface and hydrology, aerosol, ocean and sea-ice processes. It is based on a previous configuration, HadGEM1, which was used in CMIP3, but with improvements designed to address specific systematic errors [Martin et al, 2011]. The model has 38 levels in the vertical and a horizontal resolution of 1.25 Â 1.875 in latitude and longitude.…”

“…[4] The Met Office Hadley Centre has recently developed a new state-of-the-art Earth System climate model, HadGEM2-ES [Martin et al, 2011;Collins et al, 2011]. The precise definition of an Earth system climate model is somewhat arbitrary: we refer to a model that includes both terrestrial and oceanic ecosystems, as well as interactive tropospheric chemistry, and the various couplings between them [Collins et al, 2011].…”

Century‐scale perspectives on observed and simulated Southern Ocean sea ice trends from proxy reconstructions

“…This assumption may not hold true for proxy reconstructions, and a number of modifications to the standard technique have been made here to account for this complication. First, the control run segments were converted into ''pseudo-reconstructions'' by adding a reconstruction uncertainty, modeled as a random Normal time series for each sector/season with a mean of 0 and a [Gent et al, 2011] 501 5 3 CESM1-CAM5 [Hurrell et al, 2013] 235 3 1 CSIRO-Mk3-6 [Rotstayn et al, 2012] 500 5 5 FGOALS-g2 [Li et al, 2013] 700 3 3 HadGEM2-ES [Martin et al, 2011] 576 5 0 IPSL-CM5A-LR [Mignot and Bony, 2013] 1000 5 0 IPSL-CM5A-MR [Mignot and Bony, 2013] 300 3 2 MIROC-ESM [Watanabe et al, 2011] 630 3 3 MIROC5 [Watanabe et al, 2010] 670 5 0 NorESM1-M [Bentsen et al, 2012] (Table 1). Second, in general total least squares regression is used to estimate b since uncertainty in the response vector X can be accounted for [Allen and Stott, 2003;Hannart et al, 2014], but this requires a parametric estimate of the internal variability b-range that does not account for observational error.…”

A seamless approach to understanding and predicting Arctic sea ice in Met Office modelling systems

“…Improving aspects of sea ice physics can play an important role in improving simulations of sea ice [14], but the atmosphere and ocean simulations can also play a role as seen in HadGEM1 [15] where the dynamical atmosphere forcing was well represented [14]. Projections of summer Arctic sea ice area from the HadGEM2-ES climate model [16] show large losses of Arctic sea ice occurring under all scenarios; only the low emissions scenario (RCP2.6) shows a sustainable (but small) amount of summer sea ice in the late twenty-first century (figure 2). This is typical of CMIP5 projections; the multi-model ensemble means of projections from CMIP5 climate models show large losses of summer Arctic sea ice of between 43% and 94% over the twenty-first century in September for the low (RCP2.6) and high (RCP8.5) emissions scenarios, respectively [1].…”

“…Met Office climate model configured as HadGEM1 but with improvements to the physical model [16] and inclusion of Earth systems [50]. Climate projections produced with this model were submitted to CMIP5.…”