Climate forcing reconstructions for use in PMIP simulations of the last millennium (v1.0)

Abstract

Simulations of climate over the Last Millennium (850–1850 CE) have been incorporated into the third phase of the Paleoclimate Modelling Intercomparison Project (PMIP3). The drivers of climate over this period are chiefly orbital, solar, volcanic, changes in land use/land cover and some variation in greenhouse gas levels. While some of these effects can be easily defined, the reconstructions of solar, volcanic and land use-related forcing are more uncertain. We describe here the approach taken in defining the scenarios used in PMIP3, document the forcing reconstructions and discuss likely implications

Climate Change During the Holocene (Past 12,000 Years)

“…Although the general shape of the time evolution for solar irradiance is generally agreed upon, the magnitude of its variations at centennial timescales is still contended. Some authors suggest values of the order of 0.5 % of the total solar constant (Shapiro et al 2011), while others interpret the isotopic record to indicate typical changes of the order of 0.1 % (Schmidt et al 2011). The recent reconstruction by Shapiro et al (2011), displaying amplitude of centennial variations of the order of 0.5 %, has been critically assessed by the climate research community.…”

“…Past volcanic forcing can be reconstructed for recent centuries and, but with greater uncertainty, for the past few millennia by analysing the acidity of ice layers in polar ice cores (see Schmidt et al 2011 for a thorough discussion). Volcanic eruptions produce vast amounts of sulphate aerosols which are transported through the stratosphere and deposited on snow and ice.…”

Statistical framework for evaluation of climate model simulations by use of climate proxy data from the last millennium – Part 3: Practical considerations, relaxed assumptions, and using tree-ring data to address the amplitude of solar forcing

“…The last millennium -prior to the onset of the industrial era around 1850 CE -provides an opportunity to test hypotheses about the role of external drivers, in particular orbital forcing, solar variability, volcanic aerosols, land use/land cover changes and variations in greenhouse gas levels, under climate conditions relatively close to those of today (Jungclaus et al, 2010;Schmidt et al, 2011;Landrum et al, 2012;Fernández-Donado et al, 2013;Sueyoshi et al, 2013). A constantly growing number of proxy-based reconstructions and model-based simulations of past climate variations implies an increasing need for statistical methods for comparing data of the two kinds.…”

The Maunder minimum and the Little Ice Age: an update from recent reconstructions and climate simulations

“…Greenhouse gas concentrations are adopted from measurements of CO 2 , CH 4 and N 2 0 in Antarctic ice cores (Schmidt et al, 2011). The volcanic activity follows the Gao et al (2008) reconstruction, also derived from ice core records.…”

“…The volcanic activity follows the Gao et al (2008) reconstruction, also derived from ice core records. The total solar irradiance is varied according to Vieira et al (2011) which also includes spectral variations (Schmidt et al, 2011). The parameters of Earth's orbit around the sun, and the resulting changes in insolation, follow Berger (1978).…”