Reconstructing Last Glacial Maximum Seasonal Paleotemperatures Using An Energy Balance Model

Reconstruction of seasonal surface temperatures of Earth at the Last Glacial Maximum (LGM) has been a topic of attention in paleoclimatology since the pioneering work of the CLIMAP project. Previous work has demonstrated that energy balance models (EBMs) have a comparable sensitivity to atmospheric general circulation models (GCMs) for processes involving rapid responses of the climate system such as seasonal temperature changes over land. Our research, based on the energy balance between incoming insolation and outgoing terrestrial radiation, applies a linear high-resolution energy balance model to reconstruct the seasonal paleotemperature at the LGM without the constraints of sea surface temperature boundary conditions employed by GCMs.

Our EBM model robustly reconstructs seasonal paleotemperature at the LGM with a global average of 3.5°C colder than present. This result, which differs from the CLIMAP result, not only reconciles recent estimates but also agrees well with most published geological data analyses. It also suggests that the temperature anomaly in low and mid-latitudes was relatively stable within a 2-4°C range. However, high latitudes in both the Northern and Southern hemispheres experienced drastic seasonal changes. Although the global annual decrease at the LGM was ~3.5°C and seasonal variation in low and mid- latitudes was ~ 2-4°C, it is of note that seasonal anomaly in high latitudes was sufficient to trigger glacier melting. Our simulation suggests a 5.42°C increase from October to January south of 70°S and a 14.77°C rise from March to July north of 70°N. Thus, we suggest that these temperature conditions 18,000 yr BP provided an environment of climatic instability that facilitated transition from glacial to warm conditions.