PastClimates

This repository is a collection of useful data representing past climate changes. The data currently archived here are Supplements to the Review paper Past climates inform our future, published in 2020 in Science. When using these data, please cite our paper:

Tierney, J.E. et al (2020) Past climates inform our future, Science 370, eaay3701, https://doi.org/10.1126/science.aay3701

Description of files

co2Binned.csv This file contains binned estimates of past carbon dioxide levels based on multiple proxies (stomata, paleosols, algal lipids, boron isotopes). The bins are larger moving back in time, in accordance with data availability. The CO₂ proxy data include the collection of Foster et al. (2017) Nature Communications https://doi.org/10.1038/ncomms14845 as well as data published since then, including new boron (Sosdian et al., 2018 https://doi.org/10.1016/j.epsl.2018.06.017; Henehan et al., 2019 https://doi.org/10.1073/pnas.1905989116) and algal lipid (Super et al., 2018 https://doi.org/10.1130/G40228.1, Witkowski et al., 2018 https://doi.org/10.1126/sciadv.aat4556) data. For each time bin, available data and their accompanying 1-sigma lower and upper bounds were averaged together. Data with mean values below 150 ppm were excluded from the bin average on the basis that this level of CO₂ is below the lowest values observed during the Late Pleistocene glaciations from the ice core record and is therefore not physically plausible (especially for warmer Mesozoic and Cenozoic climates).

co2Smoothed.csv This file contains a resampled, smoothed version of the co2Binned.csv. The data in co2Binned.csv were resampled to 0.4 Ma timesteps and then smoothed with a Gaussian filter with a length of 8 Ma. These data are plotted in Figure 1 of Past climates inform our future.

THansenMethod.csv This file contains a reconstruction of global mean annual surface temperature. Data from 65.5-0 Ma are taken directly from Hansen et al., (2013) https://doi.org/10.1098/rsta.2012.0294. The time series is then extended back to 114.5 Ma using the Mesozoic compilation of benthic δ¹⁸O of Friedrich et al., (2012) https://doi.org/10.1130/G32701.1 and applying the same scaling method used by Hansen et al., (2013) for ice-free climates. Any δ¹⁸O data assigned to the same time interval were averaged prior to transformation to temperature.

THansenMethodSmoothed.csv This file contains a resampled, smoothed version of THansenMethod.csv. Data were resampled to 0.2 Ma timesteps and then smoothed with a Gaussian filter with a length of 6 Ma. These data are plotted in Figure 1 of Past climates inform our future.

RCPcGENIE.csv This file contains projected atmospheric CO₂ values from 1750 AD to 500,000 years in the future under the IPCC AR5 Representative Concentration Pathways. Projections use the carbon-centric Grid Enabled Integrated Earth System Model (cGEnIE), an Earth System model of intermediate complexity. These data are plotted in Figure 4 of Past climates inform our future.