Readme

This repository provides data and code to reproduce the figures of "Contrasting state-dependent effects of natural forcing on global and local climate variability" (Ellerhoff et al., 2022) published in Geophysical Research Letters: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022GL098335. The presented code is released under the Zenodo identifier https://zenodo.org/record/6474769.

Authors: Beatrice Ellerhoff, Moritz J. Kirschner, Elisa Ziegler, Kira Rehfeld

Responsibility for this repository: Beatrice Ellerhoff (@bellerhoff) and Kira Rehfeld (@krehfeld). The code builds on previous analysis by Moritz J. Kirschner (@cellador). Elisa Ziegler (@elisaziegler) helped to conduct the TransEBM simulations and their analysis (https://github.com/paleovar/TransEBM).

Related persons: Max D. Holloway, Louise Sime

Please see ./license.md for terms of use. This repository contains the maintained code and processed data to create the figures of Ellerhoff et al. (2022). The model simulation data can be found on Zenodo under the identifier 10.5281/zenodo.6074747 .

Organisation of this repository

The repository contains scripts (e.g., F2.R), input data (./data), and additional information (e.g., license.md). It is organized in a folder structure, where each folder comprises a specific analysis. To reproduce a figure from Ellerhoff et al. (2022) run the script that is named as the figure (Figure X of the main manuscript is denoted by FX.R and Figure X of the supplementary materials is denoted by FSX.R). The main directory contains scripts (.R-files) and files that define useful functions and plotting parameters.

scripts	description
F1.R- F4.R	Scripts to reproduce the figures of the main manuscript.
FS1.R- FS11.R	Scripts to reproduce the figures of the supplemental information.

directories	description
./01_characteristics/	Contains the analysis for characterizing the input data, i.e. model runs.
./02_surface_climate_response/	Contains all analysis of the surface climate response to volcanism.
./03_spectral_analysis/	Contains the spectral analysis of the effects from natural forcing on global and regional variability.
./04_variance_ratios/	Contains the variance ratio analysis for comparison of simulated to observed variance.
./data/	Contains pre-processed input data useful for plotting.
./data/HadCM3/	Empty. Please load the raw_data from the Zenodo identifier 10.5281/zenodo.6074747

additional files	description
.gitignore	Information for GIT version control to not add several file extensions to version control (e.g. *.png, *.pdf)
license.md/ license.html	Licensing information
readme.md	General README

Prerequisites

Our code requires the following R packages:

• stats
• utils
• polyclip (might additionally require Rtools)
• ncdf4
• RColorBrewer
• maps (can be obtained from https://github.com/krehfeld/nest, using devtools::install_github())
• PaleoSpec (can be obtained from https://github.com/EarthSystemDiagnostics/paleospec, using devtools::install_github())

Creating some of the figures additionally requires (separately loaded in the corresponding .R scripts):

• dplyr
• openxlsx

Generating the input data once the raw data is available on Zenodo (after publication) additionally requires:

• ncdf4
• boot
• parallel
• graphics

Data references

We thank the research groups for producing and making available their data from paleoclimate, observations, and forcing reconstructions.

Model simulations were carried out using:

• the model TransEBM E. Ziegler and K. Rehfeld, described in TransEBM v. 1.0: description, tuning, and validation of a transient model of the Earth's energy balance in two dimensions, Geoscientific Model Development (2021). Please find the current version of the model at https://github.com/paleovar/TransEBM. The first version is licensed under the GNU General Public License Version 3 and archived on Zenodo (https://doi.org/10.5281/zenodo.3941311, Ziegler and Rehfeld, 2020).
• version 3 of the Hadley Center Coupled Model, HadCM3, described in P. Valdes et al., The BRIDGE HadCM3 family of climate models: HadCM3@Bristol v1.0, Geoscientific Model Development (2017) and J. Tindall, L. Sime, P. Valdes Journal of Geophysical Research (Atmospheres) (2009) https://doi.org/10.1029/2008JD010825 . The model simulation data is published on Zenodo under the identifier 10.5281/zenodo.6074747
• the Archer UK National Supercomputing Services (www.archer.ac.uk) for HadCM3.

Paleoclimate, observational and reanalysis data were obtained from:

• Rehfeld et al., Global patterns of declining temperature variability from the Last Glacial Maximum to the Holocene, Nature (2018) https://doi.org/10.1038/nature25454
• Rayner et al.. Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century, Journal of Geophysical Research D: Atmospheres (2003) (downloaded latest version of HadISST dataset 11/2019)
• PAGES 2k Consortium, "A global multiproxy database for temperature reconstructions of the Common Era." Scientific data 4 (2017).https://dx.doi.org/10.1038%2Fsdata.2017.88

Forcing reconstructions were obtained from:

• G. A. Schmidt et al., Climate forcing reconstructions for use in PMIP simulations of the Last Millennium (v1.1), Geoscientific Model Development (2012)
• T. J. Crowley and M. B. Unterman, Technical details concerning development of a 1200 yr proxy index for global volcanism, Earth System Science Data (2013)
• F. Steinhilber et al., Total solar irradiance during the Holocene, Geophysical Research Letters (2009)
• Y. Wang et al., Modeling the Sun’s Magnetic Field and Irradiance since 1713, The Astrophysical Journal (2005)

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We acknowledge the R Core team and all package developers of packages used in this study. We thank them for their time and dedication to provide R and the packages to the public. Please see citation() for details on the R Core Team and citation("pkgname") for details on the developers of individual packages.

The study Ellerhoff et al. (2022) has been supported by funds of the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), Project No. 395588486 and Project No. 316076679, by the PalMod project (subproject no. 01LP1926C), and the Heinrich-Böll-Stiftung. HadCM3 simulations were performed on the Archer UK National Supercomputing Services. The study benefited from discussions within the CVAS working group, a working group of the Past Global Changes (PAGES) project. We thank the members of the Earth's climate and environmental dynamics and the SPACY groups for discussion at different stages of the manuscript preparation.

Please report bugs to the authors (beatrice.ellerhoff(at)stud.uni-heidelberg.de, kira.rehfeld(at)uni-tuebingen.de).

Beatrice Ellerhoff and Kira Rehfeld, April 2022