A 156 kyr smoothed history of the atmospheric greenhouse gases CO<sub>2</sub>, CH<sub>4</sub>, and N<sub>2</sub>O and their radiative forcing

Abstract

Abstract. Continuous records of the atmospheric greenhouse gases (GHGs) CO 2 , CH 4 , and N 2 O are necessary input data for transient climate simulations, and their associated radiative forcing represents important components in analyses of climate sensitivity and feedbacks. Since the available data from ice cores are discontinuous and partly ambiguous, a well-documented decision process during data compilation followed by some interpolating post-processing is necessary to obtain those desired time series. Here, we document our best possible data compilation of published ice core records and recent measurements on firn air and atmospheric samples spanning the interval from the penultimate glacial maximum (∼ 156 kyr BP) to the beginning of the year 2016 CE. We use the most recent age scales for the ice core data and apply a smoothing spline method to translate the discrete and irregularly spaced data points into continuous time series. These splines are then used to compute the radiative forcing for each GHG using well-established, simple formulations. We compile only a Southern Hemisphere record of CH 4 and discuss how much larger a Northern Hemisphere or global CH 4 record might have been due to its interpolar difference. The uncertainties of the individual data points are considered in the spline procedure. Based on the given data resolution, time-dependent cutoff periods of the spline, defining the degree of smoothing, are prescribed, ranging from 5000 years for the less resolved older parts of the records to 4 years for the densely sampled recent years. The computed splines seamlessly describe the GHG evolution on orbital and millennial timescales for glacial and glacial-interglacial variations and on centennial and decadal timescales for anthropogenic times. Data connected with this paper, including raw data and final splines, are available at https://doi

Radiocarbon Evidence for the Contribution of the Southern Indian Ocean to the Evolution of Atmospheric CO2 Over the Last 32,000 Years

“…Atmospheric CO 2 and Southern Ocean chemistry. ( a) Splice of atmospheric CO 2 records (red; Köhler et al, ) and atmospheric Δ 14 C values (black; SHCal13; Reimer et al, ). (b) Deep‐sea coral (dredges; Drake Passage) δ 11 B‐data (Rae et al, ).…”

Deglacial carbon cycle changes observed in a compilation of 127 benthic <i>δ</i><sup>13</sup>C time series (20–6 ka)

“…Thus, the δ 13 C gradients record a distinctly different signal than global mean δ 13 C. The δ 13 C gradients decrease most rapidly across two time steps, 18-17 and 12-11 ka. The first change at 18 ka is approximately synchronous with the start of atmospheric CO 2 rise (Marcott et al, 2014;Köhler et al, 2017) and a decrease of 0.3 ‰ in the δ 13 C of atmospheric CO 2 (Eggleston et al, 2016). In the Southern Ocean at 18 ka, proxy records indicate a decrease in aeolian dust deposition accompanied by lower marine productivity (Martínez-Garcia et al, 2009) and a decrease in winter sea ice cover, which likely reduced vertical stratification (Ferrari et al, 2014).…”

Siberian Permafrost Thawing Accelerated at the Bølling/Allerød and Preboreal Warm Periods During the Last Deglaciation

“…S, (d) the TS/TOC ratio, (e) the TOC content, (f) the median grain sizes, (g) X-ray diffraction diagrams of the sediment core HV05-St.2 at~13.7 and~11.0 cal. (low-Mg calcite) content (Katsuta et al, 2017), (e) the Lake Baikal VER99-G12 core Picea content (Shichi et al, 2013), (f) the uranium content (Katsuta et al, 2018), (g) global sea level change (Lambeck et al, 2014), Greenland ice core records of (h) GRIP CH 4 (Blunier et al, 2007, and reference therein), (i) atmospheric CO 2 mixing ratio from Antarctic ice cores (Köhler et al, 2017), and (j) NGRIP δ 18 O (North Greenland Ice Core Project, 2004). C: calcite, P: pyrite, Q: quartz.…”