Safe and just Earth system boundaries.

This is the final version. Available from Nature Research via the DOI in this record. Data availability The data supporting Figs. 2 and 3 are available at https://doi.org/10.6084/m9.figshare.22047263.v2 and https://doi.org/10.6084/m9.figshare.20079200.v2, respectively. We rely on other published datasets for the climate boundary16, N boundary72 (model files are at https://doi.org/10.5281/zenodo.6395016), phosphorus73,74 (scenario breakdowns are at https://ora.ox.ac.uk/objects/uuid:d9676f6b-abba-48fd-8d94-cc8c0dc546a2, and a summary of agricultural sustainability indicators is at https://doi.org/10.5281/zenodo.5234594), current N surpluses129,130 (the repository at https://dataportaal.pbl.nl/downloads/IMAGE/GNM) with the critical N surplus limit72 subtracted, and estimated subglobal P concentration in runoff based on estimated P load to freshwater131 and local runoff data132,133. Current functional integrity is calculated from the European Space Agency WorldCover 10-metre-resolution land cover map (https://esa-worldcover.org/en). The safe boundary and current state for groundwater are derived from the Gravity Recovery And Climate Experiment (http://www2.csr.utexas.edu/grace/RL06_mascons.html) and the Global Land Data Assimilation System (https://disc.gsfc.nasa.gov/datacollection/GLDAS_NOAH025_3H_2.1.html). More information is available in ‘Code availability’ and Supplementary Methods. Source data for Fig. 2 are provided with this paper.Code availability: The code used to produce Figs. 2 and 3 are available at https://doi.org/10.6084/m9.figshare.22047263.v2 and https://doi.org/10.6084/m9.figshare.20079200.v2, respectively. The code used to make the nutrient Earth system boundary layers in Fig. 3 is available at https://doi.org/10.5281/zenodo.7636716. The code used to make the surface water layer in Fig. 3 and derive the subglobal Earth system boundaries for surface water is available at https://doi.org/10.5281/zenodo.7674802. The code to estimate current functional integrity is available at https://figshare.com/articles/software/integrity_analysis/22232749/2. The code to derive the groundwater layer in Fig. 3 and derive the total annual groundwater recharge is available at https://doi.org/10.5281/zenodo.7710540.The stability and resilience of the Earth system and human well-being are inseparably linked1-3, yet their interdependencies are generally under-recognized; consequently, they are often treated independently4,5. Here, we use modelling and literature assessment to quantify safe and just Earth system boundaries (ESBs) for climate, the biosphere, water and nutrient cycles, and aerosols at global and subglobal scales. We propose ESBs for maintaining the resilience and stability of the Earth system (safe ESBs) and minimizing exposure to significant harm to humans from Earth system change (a necessary but not sufficient condition for justice)4. The stricter of the safe or just boundaries sets the integrated safe and just ESB. Our findings show that justice considerations constrain the integrated ESBs more than safety considerations for climate and atmospheric aerosol loading. Seven of eight globally quantified safe and just ESBs and at least two regional safe and just ESBs in over half of global land area are already exceeded. We propose that our assessment provides a quantitative foundation for safeguarding the global commons for all people now and into the future.Stockholm Universit

Influence of Last Glacial Maximum boundary conditions on the global water isotope distribution in an atmospheric general circulation model

To understand the validity of δ¹⁸O proxy records as indicators of past temperature change, a series of experiments was conducted using an atmospheric general circulation model fitted with water isotope tracers (Community Atmosphere Model version 3.0, IsoCAM). A pre-industrial simulation was performed as the control experiment, as well as a simulation with all the boundary conditions set to Last Glacial Maximum (LGM) values. Results from the pre-industrial and LGM simulations were compared to experiments in which the influence of individual boundary conditions (greenhouse gases, ice sheet albedo and topography, sea surface temperature (SST), and orbital parameters) were changed each at a time to assess their individual impact. The experiments were designed in order to analyze the spatial variations of the oxygen isotopic composition of precipitation (δ¹⁸O_precip) in response to individual climate factors. The change in topography (due to the change in land ice cover) played a significant role in reducing the surface temperature and δ¹⁸O_precip over North America. Exposed shelf areas and the ice sheet albedo reduced the Northern Hemisphere surface temperature and δ¹⁸O_precip further. A global mean cooling of 4.1 °C was simulated with combined LGM boundary conditions compared to the control simulation, which was in agreement with previous experiments using the fully coupled Community Climate System Model (CCSM3). Large reductions in δ¹⁸O_precip over the LGM ice sheets were strongly linked to the temperature decrease over them. The SST and ice sheet topography changes were responsible for most of the changes in the climate and hence the δ¹⁸O_precip distribution among the simulations