Atmospheric CO2 fluctuations during the last millennium reconstructed by stomatal frequency analysis of Tsuga heterophylla needles

Abstract

A stomatal frequency record based on buried Tsuga heterophylla needles reveals significant centennial-scale atmospheric CO 2 fluctuations during the last millennium. The record includes four CO 2 minima of 260-275 ppmv (ca. A.D. 860 and A.D. 1150, and less prominently, ca. A.D. 1600 and 1800). Alternating CO 2 maxima of 300-320 ppmv are present at A.D. 1000, A.D. 1300, and ca. A.D. 1700. These CO 2 fluctuations parallel global terrestrial air temperature changes, as well as oceanic surface temperature fluctuations in the North Atlantic. The results obtained in this study corroborate the notion of a continuous coupling of the preindustrial atmospheric CO 2 regime and climate.

A role for atmospheric CO 2 in preindustrial climate forcing

“…For the last millennium, pronounced preindustrial CO 2 variability has been reconstructed on the basis of needles of Tsuga heterophylla (western hemlock) from Mount Rainier, Washington, USA (29), and leaf remains of Quercus robur (English oak) from the southeastern part of the Netherlands (27,30). The timing of the detected CO 2 changes is in good agreement with perturbations observed in Antarctic ice core records.…”

“…It is likely that, analogous to early Holocene CO 2 changes (25-28), depletion and restoration of atmospheric CO 2 between A.D. 1000 and 1500 was driven mainly by short-term perturbations of sea-surface temperature and/or salinity. Similar to the CO 2 trend based on Tsuga heterophylla needles (29), within the dating uncertainties, the present stomata-based CO 2 reconstruction correlates to a large extent with proxy sea-surface temperature records from various parts of the North Atlantic Ocean (36)(37)(38).…”

On the reconstruction of plant photosynthetic and stress physiology across the Triassic–Jurassic boundary

“…stress physiology in a manner analogous to that employed in stomatal reconstructions of paleo-[CO 2 ] (McElwain et al, 1999;Kouwenberg et al, 2005;Kürschner et al, 2008) and also to inferences of carbon gain and nutrient usage based upon leaf shape economics (Poorter and Bongers, 2006). As the TJB is considered to represent an interval where plant thermal stress caused by excess leaf energy drove biodiversity loss (McElwain et al, 1999(McElwain et al, , 2007, this approach may assist in understanding the underlying physiological mechanisms that led to the plant responses evident in the fossil record.…”

Climatic Changes: Anthropogenic Influence or Naturally Induced Phenomenon

“…Paleobotanists can take fossilized leaves and count the number of stomata and therefore get a fairly good picture of how much carbon dioxide was in the atmosphere at the time the leaves died (Kurshner et al, 1996;Beerling et al, 1998;Wagner et al, 1999;Kouwenberg et al, 2003;Kouwenberg, 2004;Kouwenberg et al, 2005), (Figs 11,12). The second one assumes that, over time, the concentrations of the various atmospheric gasses are locked when the air bubble is "trapped" in ice.…”