DOI: 10.5061/dryad.ncjsxksvn
title: Varied oxygen simulations with WACCM6 (Proterozoic to pre-industrial atmosphere)

description: The history of molecular oxygen (O2) in Earth’s atmosphere is still
 debated; however, geological evidence supports at least two major episodes
 where O2 increased by an order of magnitude or more: the Great Oxidation
 Event (GOE) and the Neoproterozoic Oxidation Event.
 O2 concentrations have likely fluctuated (between 10−3 and 1.5
 times the present atmospheric level) since the GOE ∼ 2.4 Gyr ago,
 resulting in a time-varying ozone (O3) layer. Using a three-dimensional
 (3D) chemistry climate model, we simulate changes in O3 in Earth’s
 atmosphere since the GOE and consider the implications for surface
 habitability, and glaciation during the Mesoproterozoic. We find lower O3
 columns (reduced by up to 4.68 times for a given O2 level) compared to
 previous work; hence, higher fluxes of biologically harmful UV radiation
 would have reached the surface. Reduced O3 leads to enhanced tropospheric
 production of the hydroxyl radical (OH) which then substantially reduces
 the lifetime of methane (CH4). We show that a CH4 supported greenhouse
 effect during the Mesoproterozoic is highly unlikely. The reduced O3
 columns we simulate have important implications for astrobiological and
 terrestrial habitability, demonstrating the relevance of 3D
 chemistry-climate simulations when assessing paleoclimates and the
 habitability of faraway worlds.
description: The data was originally produced using the Earth System Model
 WACCM6. The corresponding paper that describes WACCM can be found at the
 following DOI: https://doi.org/10.1029/2019JD030943. WACCM6 is a model
 configuration of the Community Earth System Model version 2 (CESM2). We
 used CESM2.1.3, which can be downloaded from the following URL:
 https://www.cesm.ucar.edu/models/cesm2/release_download.html. 
 The atmospheric data from each simulation was output in terms of
 monthly means (h0 files; h for history), and 5 day averages (h2 files).
 For both h0 and h2 files, the last 4 years of each simulation was averaged
 using netCDF operators. ncra for time average (h0 and h2 files), and ncwa
 -alon for zonal mean (h2 files).  The data has been
 processed using the Python programming language. Two .py files are
 included named O3_FYSP_paper.py and Analysis_Functions.py. The python
 files may not be well-commented in all places. To
 produce the solar file which represent the Sun 2 billion years ago (2
 Gyr), we used an existing solar model by Claire et al. 2012
 (https://doi.org/10.1088/0004-637X/757/1/95). The model can be downloaded
 here:
 http://depts.washington.edu/naivpl/content/models/solarflux
 The datasets Kasting_Catling_Fig10_data.csv and
 ROCKE3D_Fig3_O3_col.csv are from the following papers:
 https://doi.org/10.1146/annurev.astro.41.071601.170049 and
 https://doi.org/10.3847/1538-4365/aa7a06, respectively. The data was
 recovered using WebPlotDigitizer
 (https://automeris.io/WebPlotDigitizer/).
description: To use the data: The data can be downloaded
 and processed using Python or a programming language that can handle
 netCDF data. The python (.py) files included were used by the authors for
 producing figures and analysis for the corresponding research article to
 this dataset. To use the python files, you need to correctly set up the
 paths to the correct directories and files in O3_FYSP_paper.py and
 Analysis_Functions.py. h0 files should be in path +
 'Ozone_CH4_paper/h0/', h2 files in path +
 'Ozone_CH4_paper/h2/', and solar files in path +
 'Ozone_CH4_paper/Solar_files/'. The path can be any directory
 you have permissions for. For example, on a Linux system, using
 /localhome/user/ is how the path was set up for the python file when used
 by the authors. To run the python code, run the O3_FYSP_paper.py file. If
 you have not used python before, downloading python via Anaconda and
 installing xarray should allow you to see the code (see here:
 https://www.anaconda.com/products/individual, and here:
 http://xarray.pydata.org/en/stable/getting-started-guide/installing.html).
 Figures produced will be deposited into: path +
 'Ozone_CH4_paper/  The h0 and h2 files correspond
 to the following simulations, which are described in Table 1 of the
 associated manuscript: PI:
 b.e21.BWma1850.f19_g17.baseline.cam.h0.0014-0017.nc;
 b.e21.BWma1850.f19_g17.baseline.cam.h2.0014-0017.zm.nc<br> 150% PAL:
 b.e21.BWma1850.f19_g17.150pc_o2.002.cam.h0.0034-0037.nc;
 b.e21.BWma1850.f19_g17.150pc_o2.002.cam.h2.0034-0037.zm.nc  <br> 50%
 PAL: b.e21.BWma1850.f19_g17.50pc_o2.002.cam.h0.0030-0033.nc;
 b.e21.BWma1850.f19_g17.50pc_o2.002.cam.h2.0030-0033.zm.nc<br> 10%
 PAL: b.e21.BWma1850.f19_g17.10pc_o2.001.cam.h0.0034-0037.nc;
 b.e21.BWma1850.f19_g17.10pc_o2.001.cam.h2.0034-0037.zm.nc  <br> 5%
 PAL: b.e21.BWma1850.f19_g17.5pc_o2.002.cam.h0.0032-0035.nc;
 b.e21.BWma1850.f19_g17.5pc_o2.002.cam.h2.0032-0035.zm.nc<br> 1% PAL:
 b.e21.BWma1850.f19_g17.1pc_o2.cam.h0.0028-0031.nc;
 b.e21.BWma1850.f19_g17.1pc_o2.cam.h2.0028-0031.zm.nc<br> CH4 em1:
 b.e21.BWma1850.f19_g17.1pc_o2.CH4_flux.001.cam.h0.0044-0047.nc<br>
 CH4 em0.1:
 b.e21.BWma1850.f19_g17.1pc_o2.0.1PD_CH4_flux.001.cam.h0.0044-0047.nc<br> YS: b.e21.BWma1850.f19_g17.1pc_o2.YoungSun.004.cam.h0.0060-0063.nc<br> YS 4xCO2: b.e21.BWma1850.f19_g17.1pc_o2.YoungSun.4xCO2.005.cam.h0.0089-0092.nc<br> 0.5% PAL: b.e21.BWma1850.f19_g17.0.5pc_o2.001.cam.h0.0046-0049.nc; b.e21.BWma1850.f19_g17.0.5pc_o2.001.cam.h2.0046-0049.zm.nc<br> 0.1% PAL: b.e21.BWma1850.f19_g17.0.1pc_o2.001.cam.h0.0080-0083.nc; b.e21.BWma1850.f19_g17.0.1pc_o2.001.cam.h2.0080-0083.zm.nc In addition, there are four files for calculating the three major loss channels of methane (see Fig. 8 in the associated article at https://doi.org/10.1098/rsos.211165):<br> PI: b.e21.BWma1850.f19_g17.baseline.cam.h2.CH4_loss.0014-0017.zm.nc<br> 10% PAL: b.e21.BWma1850.f19_g17.10pc_o2.001.cam.h2.CH4_loss.0034-0037.zm.nc<br> 1% PAL: b.e21.BWma1850.f19_g17.1pc_o2.cam.h2.CH4_loss.0028-0031.zm.nc<br> 0.1% PAL: b.e21.BWma1850.f19_g17.0.1pc_o2.001.cam.h2.CH4_loss.0080-0083.zm.nc Note that b.e21.BWma1850 corresponds to a WACM6 (CESM2.1) pre-industrial (year 1850) simulation. f19_g17 describes the grid setup. 96 x 144 latitude x longitude, corresponding to 1.875 degrees x 2.5 degrees. The model years of the dataset are given by 0014-0017, for years 14, 15, 16, and 17. 'zm' means a zonal mean was applied to the file. A file is provided which contains gaussian weights for the area of grid cells (gaussian weights vary with latitude):  GW_File.nc Solar files are as follows: Present day Sun: SolarForcingCMIP6piControl_c160921.nc<br> Sun's spectrum 2 Gyr ago (2.0 Ga): SolarForcingCMIP6piControl_c160921_2.0Ga.nc