Historical and idealized climate model experiments: an EMIC intercomparison

Abstract

Both historical and idealized climate model experiments are performed with a variety of Earth System Models of Intermediate Complexity (EMICs) as part of a community contribution to the Intergovernmental Panel on Climate Change Fifth Assessment Report. Historical simulations start at 850 CE and continue through to 2005. The standard simulations include changes in forcing from solar luminosity, Earth's orbital configuration, CO<sub>2</sub>, additional greenhouse gases, land-use, and sulphate and volcanic aerosols. In spite of very different modelled pre-industrial global surface air temperatures, overall 20th century trends in surface air temperature and carbon uptake are reasonably well simulated when compared to observed trends. Land carbon fluxes show much more variation between models than ocean carbon fluxes, and recent land fluxes seem to be underestimated. It is possible that recent modelled climate trends or climate-carbon feedbacks are overestimated resulting in too much land carbon loss or that carbon uptake due to CO<sub>2</sub> and/or nitrogen fertilization is underestimated. <br><br> Several one thousand year long, idealized, 2x and 4x CO<sub>2</sub> experiments are used to quantify standard model characteristics, including transient and equilibrium climate sensitivities, and climate-carbon feedbacks. The values from EMICs generally fall within the range given by General Circulation Models. Seven additional historical simulations, each including a single specified forcing, are used to assess the contributions of different climate forcings to the overall climate and carbon cycle response. The response of surface air temperature is the linear sum of the individual forcings, while the carbon cycle response shows considerable synergy between land-use change and CO<sub>2</sub> forcings for some models. Finally, the preindustrial portions of the last millennium simulations are used to assess historical model carbon-climate feedbacks. Given the specified forcing, there is a tendency for the EMICs to underestimate the drop in surface air temperature and CO<sub>2</sub> between the Medieval Climate Anomaly and the Little Ice Age estimated from paleoclimate reconstructions. This in turn could be a result of errors in the reconstructions of volcanic and/or solar radiative forcing used to drive the models or the incomplete representation of certain processes or variability within the models. Given the datasets used in this study, the models calculate significant land-use emissions over the pre-industrial. This implies that land-use emissions might need to be taken into account, when making estimates of climate-carbon feedbacks from paleoclimate reconstructions

Different mechanisms of silicic acid leakage and their biogeochemical consequences

“…The interior ocean ventilation of MESMO 2 is well calibrated against measured and derived tracers such as natural and bomb radiocarbon, anthropogenic carbon, and chlorofluorocarbon. The model is successfully used in a number of process studies of the global carbon and climate [Chikamoto et al, 2008;Lee et al, 2011;Matsumoto and McNeil, 2013;Matsumoto et al, 2010;Matsumoto and Yokoyama, 2013;Sun and Matsumoto, 2010;Ushie and Matsumoto, 2012] as well as in community-wide model intercomparison projects [Archer et al, 2009;Cao et al, 2009;Eby et al, 2013;Joos et al, 2012;Weaver et al, 2012;Zickfeld et al, 2013].…”

MESMO 2: a mechanistic marine silica cycle and coupling to a simple terrestrial scheme

“…The model is also well calibrated on centennial time scale with respect to the abundance of natural 14 C ( 14 C) in the deep Pacific and Indian. MESMO 1 has been used successfully in a number of carbon and climate process studies (Lee et al, 2011;Matsumoto and McNeil, 2013;Matsumoto and Yokoyama, 2013;Sun and Matsumoto, 2010;Ushie and Matsumoto, 2012) as well as in model intercomparison projects Eby et al, 2012;Weaver et al, 2012;Zickfeld et al, 2012).…”

Impact of climate changes over the extratropical land on permafrost dynamics under RCP scenarios in the 21st century as simulated by the IAP RAS climate model

“…The computations were carried out using the global climate model worked out at the Obukhov Institute of Atmospheric Physics of the Russian Academy of Sciences (IAP RAS CM) referred to the class of models of intermediate complexity [31,33,40] and including the blocks of the transport of short-and long-wave radiation, convection, cloud and precipitation formation, and carbon (including methane) cycle as well as the detailed block of processes of heat and moisture transport in the soil [3,5,7,12,19].…”

“…It should be noted that the modern climate models of intermediate complexity describe quite realistically the climate response to the external impact [33]; in particular, IAP RAS CM simulates well the preindustrial and current state of the climate system as well as the general characteristics of climate changes in recent centuries [19]. During the numerical experiments for the 21st century, the variations of concentration of anthropogenic greenhouse gases were specified according to the RCP (Representative Concentration Pathways) 2.6 (the least aggressive), 4.5, 6.0 (moderate), and 8.5 (the most aggressive) scenarios.…”