Status: this preprint is open for discussion and under review for Climate of the Past (CP).
Reconstructing Holocene temperatures in time and space using paleoclimate data assimilation
Michael P. Erb1,Nicholas P. McKay1,Nathan Steiger2,3,Sylvia Dee4,Chris Hancock1,Ruza F. Ivanovic5,Lauren J. Gregoire5,and Paul Valdes6Michael P. Erb et al.Michael P. Erb1,Nicholas P. McKay1,Nathan Steiger2,3,Sylvia Dee4,Chris Hancock1,Ruza F. Ivanovic5,Lauren J. Gregoire5,and Paul Valdes6
Abstract. Paleoclimatic records provide valuable information about Holocene climate, revealing aspects of climate variability for a multitude of sites around the world. However, such data also possess limitations. Proxy networks are spatially uneven, seasonally biased, uncertain in time, and present a variety of challenges when used in concert to illustrate the complex variations of past climate. Paleoclimatic data assimilation provides one approach to reconstructing past climate that can account for the diverse nature of proxy records while maintaining the physics-based covariance structures simulated by climate models. Here, we use paleoclimate data assimilation to create a spatially-complete reconstruction of temperature over the past 12,000 years using proxy data from the Temperature 12k database and output from transient climate model simulations. Following the last glacial period, the reconstruction shows Holocene temperatures warming to a peak near 6,400 years ago followed by a slow cooling toward the present day, supporting a preindustrial global mean surface temperature maximum during the mid-Holocene. Sensitivity tests show that if proxies have an overlooked summer bias, some apparent mid-Holocene warmth could actually represent summer trends rather than annual mean trends. Regardless, the potential effects of proxy seasonal biases are insufficient to align reconstructed global mean temperature with the warming trends seen in transient model simulations.
Holocene temperature reconstruction using paleoclimate data assimilationMichael P. Erb, Nicholas P. McKay, Nathan Steiger, Sylvia Dee, Chris Hancock, Ruza F. Ivanovic, Lauren J. Gregoire, and Paul Valdes https://doi.org/10.5281/zenodo.6426332
To look at climate over the past 12000 years, we reconstruct spatial temperature using natural climate archives and information from model simulations. We see mild global mean warm around 6000 years ago, which differs somewhat from past reconstructions. If more of our data represents summer values, this could explains some of the observed temperature change, but it still wouldn't explain the large difference between many reconstructions and climate models over this period.
To look at climate over the past 12000 years, we reconstruct spatial temperature using natural...