SPATIAL MODEL-DATA COMPARISON OF MID-HOLOCENE TEMPERATURES

Paleoclimate proxy data and transient climate model simulations disagree on whether global temperature warmed or cooled from the early Holocene to pre-Industrial times, a result that has been called the “Holocene Temperature Conundrum.” This disagreement has important implications for evaluating climate models and understanding sensitivity to various climatic forcing factors. Researchers have explored a number of ways of reconciling the divergent global trends, including considering the seasonality of proxy reconstructions and their spatial representativeness, as well as the possibility of model biases. Here, we examine spatial patterns of temperature change for a Mid-Holocene time slice (5,000 – 7,000 years ago) to assess model-data agreement on regional scales. We compiled temperature reconstructions from several public data repositories, including multiple proxy types and both marine and continental sites. For these reconstructions, we consider possible seasonal biases in the proxies as well as several sources of reconstruction uncertainty. Model simulations we use for comparison include multiple transient simulations of the Holocene as well as available 6 ka simulations of the Coupled Model Intercomparison Project Phase 6/Paleoclimate Modelling Intercomparison Project Phase 4 (CMIP6/PMIP4). Results have implications for understanding model-data divergence at the global scale, as well as regional-scale climate responses that are relevant for local impacts.