Quantitative Late Quaternary climate reconstruction from plant macrofossil proxy in Western North America

Abstract

The Late Quaternary packrat (Neotoma spp.) midden plant macrofossil record in western North America is an exceptional record of biotic change that provides strong evidence of past climate. In this study we generate quantitative estimates of climate from plant community composition of more than 600 individual paleomiddens over the past 50,000 years. This is the first large-scale application of CRACLE, a quantitative climate inference method that uses plant community composition as a climatic proxy under and individualistic concept of plant community assembly. The results are spatiotemporally specific estimates of temperature, precipitation, available moisture, and seasonal patterns that are consistent with well understood global climate patterns, but provide previously unavailable detail and precision of the regional paleoclimate in western North America. Rapid warming is estimated at the Pleistocene-Holocene transition, at a conservative estimate of ca. 1 degree centigrade per millennium. Previously projected future temperature increases suggest a rate of increase of more than 2 degrees over the next century, an astonishing 10X the rate experienced at any point during the past 50,000 years in Western North America. These analyses form a baseline demonstration of how the growing paleoecological record of packrat midden plant macrofossils is able to provide quantitative estimates of paleoclimate that aid in understanding the complexities of, and biotic responses to the regional climate system.