ALBERT

Description: The atmospheric concentration of CO2 at which global glaciation (snowball) bifurcation occurs, changes throughout Earth's history, most notably because of the slowly increasing solar luminosity. Quantifying this critical CO2 concentration is not only interesting from a climate dynamics perspective, but also an important prerequisite for understanding past Snowball Earth episodes as well as the conditions for habitability on Earth and other planets. Here we use the coupled climate model CLIMBER-3α in an Aquaplanet configuration to scan for the Snowball bifurcation point for time slices spanning the last 4 billion years, thus quantifying the time evolution of the bifurcation and identifying a qualitative shift in critical state dynamics.

Description: The new climate dataset, BASD-CMIP6-PE, for Peru and Ecuador is based on bias-adjusted and statistically downscaled CMIP6 climate projections from 10 GCMs. It addresses the need for reliable high-resolution (1d, 10km) climate data covering Peru and Ecuador. This dataset includes historical simulations (1850-2014) and future projections (2015-2100) for precipitation and minimum, mean, and maximum temperature under three Shared Socioeconomic Pathways (SSPs:SSP1-2.6, SSP3-7.0, and SSP5-8.5). The BASD-CMIP6-PE climate data were generated using the trend-preserving Bias Adjustment and Statistical Downscaling (BASD) method (Lange, 2019, 2021) and data from regional observational datasets such as RAIN4PE (Fernandez-Palomino et al., 2021a,b) for precipitation and PISCO-temperature (Huerta et al., 2018) for temperatures as reference data. The reliability of the BASD-CMIP6-PE was evaluated using observational data and through hydrological modeling across Peruvian and Ecuadorian river basins in the historical period. The evaluation demonstrated the dataset’s reliability in describing spatial patterns of atmospheric variables and streamflow simulation, including mean, low, and high flows. This suggests the usefulness of the new dataset for assessing regional climate change impacts on agriculture, water resources, and hydrological extremes. The BASD-CMIP6-PE data are available for the domain covering Peru and Ecuador, located between 19°S and 2°N and 82°W to 67°W, with a spatial resolution of 0.1° and a daily temporal resolution. The unit for precipitation is millimeters (mm), and for temperature, it is degrees Celsius (°C). The BASD-CMIP6-PE dataset is organized within a "daily" folder, denoting its availability at a 1 daily temporal resolution. Within this directory, four subfolders are present: "historical" containing historical data, "ssp126" for SSP1-2.6, "ssp370" for SSP3-7.0, and "ssp585" for SSP5-8.5. Each of these subfolders further includes ten distinct folders, corresponding to different GCMs: CanESM5, IPSL–CM6A–LR, UKESM1–0–LL, CNRM–CM6–1, CNRM–ESM2–1, MIROC6, GFDL–ESM4, MRI–ESM2–0, MPI–ESM1–2–HR, and EC–Earth3. These folders store the data in the NetCDF format arranged by model, model member, experiment, variable, temporal resolution, and subset period, resulting in file names like "canesm5_r1i1p1f1_ssp126_pr_daily_2015_2020.nc". For a detailed description of the BASD-CMIP6-PE development and evaluation, readers are advised to read Fernandez-Palomino et al. (2023), for which this dataset is supplementary material.

Description: The atmosphere model of the Geophysical Fluid Dynamics Laboratory (GFDL-AM2) is coupled to a slab ocean in order to analyse the monsoon's sensitivity to changes in various forcing parameters on a planet with idealized topography. This monsoon planet design of a water planet with a zonal circumglobal land stripe allows to extract the relevant monsoon behaviour and reduces the influence of topography. Besides the width and location of the land stripe, the atmospheric CO2 concentration, incoming solar radiation, sulfate aerosol concentration and surface albedo are variied. Horizontal grid resolution is 2° latitude x 2.5° longitude. For the vertical grid, a hybrid coordinate grid with 24 vertical levels is implemented. The lowest model level starts about 30 m above the surface and the top level is at about 3 hPa. The vertical resolution is decreasing towards higher altitudes. Advective and physics time steps are 10 minutes and 0.5 hours, for atmopsheric radiation 3 hours time steps are used. Instead of an ocean general circulation model, a mixed-layer slab ocean is used.