A multi-model assessment of last interglacial temperatures

Abstract

The last interglaciation (-130 to 116 ka) is a time period with a strong astronomically induced seasonal forcing of insolation compared to the present. Proxy records indicate a significantly different climate to that of the modern, in particular Arctic summer warming and higher eustatic sea level. Because the forcings are relatively well constrained, it provides an opportunity to test numerical models which are used for future climate prediction. In this paper we compile a set of climate model simulations of the early last interglaciation (130 to 125 ka), encompassing a range of model complexities. We compare the simulations to each other and to a recently published compilation of last interglacial temperature estimates.We show that the annual mean response of the models is rather small, with no clear signal in many regions. However, the seasonal response is more robust, and there is significant agreement amongst models as to the regions of warming vs cooling. However, the quantitative agreement of the model simulations with data is poor, with the models in general underestimating the magnitude of response seen in the proxies. Taking possible seasonal biases in the proxies into account improves the agreement, but only marginally. However, a lack of uncertainty estimates in the data does not allow us to draw firm conclusions. Instead, this paper points to several ways in which both modelling and data could be improved, to allow a more robust model-data comparison. © Author(s) 2013

The last interglacial climate: comparing direct and indirect impacts of insolation changes

“…While these patterns agree qualitatively with proxy reconstructions, the models generally underestimate the magnitude of the changes Masson-Delmotte et al 2013;Lunt et al 2013;Otto-Bliesner et al 2013). Several models have the strongest warming occurring in the North Atlantic region as a consequence of retreating sea ice and changes in the ocean circulation (Fischer and Jungclaus 2010;Lunt et al 2013;Nikolova et al 2013;Otto-Bliesner et al 2013).…”

“…Seasonally, the models consistently simulate warming over Northern Hemisphere continents during summer (June-July-August; JJA) and global cooling (except in the Arctic) during winter (December-January-February, DJF) (Lunt et al 2013;Nikolova et al 2013;Otto-Bliesner et al 2013;Langebroek and Nisancioglu 2014). While these patterns agree qualitatively with proxy reconstructions, the models generally underestimate the magnitude of the changes Masson-Delmotte et al 2013;Lunt et al 2013;Otto-Bliesner et al 2013). Several models have the strongest warming occurring in the North Atlantic region as a consequence of retreating sea ice and changes in the ocean circulation (Fischer and Jungclaus 2010;Lunt et al 2013;Nikolova et al 2013;Otto-Bliesner et al 2013).…”

“…Recent model assessments find very low global annual mean warming during LIG, contrasting the proxy reconstruction estimate of 1-2 K warming (Masson-Delmotte et al 2013;Otto-Bliesner et al 2013). The latest IPCC report estimates a multi-model annual mean surface warming of 0.0 ± 0.5 K (Masson-Delmotte et al 2013), while Lunt et al (2013) find warming in the Arctic and cooling in the African and Indian monsoon regions as the only robust annual mean results in their intercomparison of 14 models. Seasonally, the models consistently simulate warming over Northern Hemisphere continents during summer (June-July-August; JJA) and global cooling (except in the Arctic) during winter (December-January-February, DJF) (Lunt et al 2013;Nikolova et al 2013;Otto-Bliesner et al 2013;Langebroek and Nisancioglu 2014).…”

“…Transient simulations usually rely on earth system models of intermediate complexity , while general circulation models (GCMs) primarily are employed for equilibrium, snapshot simulations (Fischer and Jungclaus 2010;Govin et al 2012;Lunt et al 2013;Nikolova et al 2013;Otto-Bliesner et al 2013;Langebroek and Nisancioglu 2014). Recent model assessments find very low global annual mean warming during LIG, contrasting the proxy reconstruction estimate of 1-2 K warming (Masson-Delmotte et al 2013;Otto-Bliesner et al 2013).…”

“…The latest IPCC report estimates a multi-model annual mean surface warming of 0.0 ± 0.5 K (Masson-Delmotte et al 2013), while Lunt et al (2013) find warming in the Arctic and cooling in the African and Indian monsoon regions as the only robust annual mean results in their intercomparison of 14 models. Seasonally, the models consistently simulate warming over Northern Hemisphere continents during summer (June-July-August; JJA) and global cooling (except in the Arctic) during winter (December-January-February, DJF) (Lunt et al 2013;Nikolova et al 2013;Otto-Bliesner et al 2013;Langebroek and Nisancioglu 2014). While these patterns agree qualitatively with proxy reconstructions, the models generally underestimate the magnitude of the changes Masson-Delmotte et al 2013;Lunt et al 2013;Otto-Bliesner et al 2013).…”