Challenges in quantifying Pliocene terrestrial warming revealed by data–model discord

Abstract

Tel:Tel. +44 (0) 44The zonal averages from each of the eight models ( Fig. 1) 87( Fig. 3a). Proxy-based Pliocene SAT anomalies display a similar trend for the temperate and 88 polar zones of the Northern Hemisphere (Fig. 3b) 133 Conclusion and Implication 134Our DMC identifies a cold bias in models in the Northern Hemisphere (particularly north of 30 135 °N) demonstrating that, given the boundary conditions we have applied, none of the models 136 used in this study reproduce the magnitude of northern hemisphere high-latitude warming 137 exhibited in this proxy-dataset (Fig. 3c). A tentative data model mismatch may also be evident in 138 the tropical zone where modelled Pliocene SATs appear to be too high, however this is limited 139 by data availability. 140Before drawing any conclusions with regard to the ability of climate models to reproduce the 141 Pliocene, the potential causes of mismatches between palaeo-data and -models must be fully 142 understood. Our DMC has identified regions (i.e. northern Russia, North Alaska and northeast 143 Australia) where our data model mismatch is apparent when considering bioclimatic range (Fig. 144 3d), temporal variability (Fig. 3e) and even a combination of both factors (Fig. 3f). We have 145 qualitatively assessed these sites as 'medium' to 'very high confidence'. The underlying reasons 146 for these large DMC mismatches are still unknown. 147Our DMC results also demonstrate that at many localities the spread in model-predicted SAT 148 anomalies, from the model ensemble, is sufficiently large to cause an overlap with the available 149 range of proxy-derived SAT anomalies (highlighted by the purple squares in Fig. 3g). At these 193Acknowledgements 194

Evaluating the dominant components of warming in Pliocene climate simulations

“…However, the recently begun Pliocene Model Intercomparison Project is the first time that coordinated multi-model experiments, with common boundary conditions and experimental protocols, have been undertaken. The warming seen in the Pliocene has been well documented from a wide variety of sites from across the globe and using a number of different proxy techniques (Dowsett et al, 2012;Salzmann et al, 2013). This primarily shows changes due to specified vegetation and global ice sheets and modelled sea ice and snow cover, although it includes an atmospheric component.…”

“…This paper focuses on PlioMIP Experiment 2, designed for coupled oceanatmosphere GCMs . Although, many of the large-scale features of the simulated Pliocene climate have been well documented (Dowsett et al, 2012;Haywood et al, 2013;Zhang et al, 2013Zhang et al, , 2013aSalzmann et al, 2013), the causes of the simulated changes and differences between the simulations have not been extensively explored prior to this study. In this paper the energy balance of the PlioMIP Experiment 2 simulations are analysed in order to understand the causes of Pliocene atmospheric warming and the latitudinal distribution of increased surface air temperatures.…”

The effect of a dynamic soil scheme on the climate of the mid-Holocene and the Last Glacial Maximum

“…The simulation of this polar amplification is a key challenge for current model approaches (e.g. Knorr et al, 2011;Krapp and Jungclaus, 2011;Fedorov et al, 2013;Salzmann et al, 2013). To provide a potential solution for the model-data discrepancy, numerous studies provoke processes for polar amplification, dealing with energy balance and heat transport changes (e.g.…”

Twenty-million-year relationship between mammalian diversity and primary productivity

“…Paleo-climatic data were obtained from several public sources that covered the Neogene as a whole (18), exclusively the Miocene (45), or exclusively the Pliocene (46,47). We used terrestrial estimates of mean annual temperature (MAT) and precipitation (MAP) inferred from fossil plant communities which allowed us to calculate spatially explicit values of terrestrial NPP for each region or continent.…”