Fig. 1: Characteristics of bioarchaeological and environmental proxy archives.

The bioarchaeological samples are (from left to right): hair, nail, tooth, bones with short or long turnover rates, bones from young animals/individuals, and charred grains. The temporal depth varies between proxies, yet the palaeontology and bioarchaeology hardly provide any continuous time series and the bioarchaeological sample frequency is considerably reduced towards the oldest samples. The dating uncertainty or precision can reach one calendar year for tree-rings, speleothems, varved lake’s sediments, speleothems, young ice cores, corals and molluscs, but it can be decadal to millennial for most proxies depending on the temporal depth and the datation method. The proxy resolution varies from sub-annual to decadal for most proxies, it can be (multi-)centennial for marine sediments and other layers that form slowly. The global spatial distribution vary between proxies: ice cores depend on global glacier distribution (light blue signature; source: https://wgms.ch/downloads/DOI-WGMS-FoG-2025-02b.zip); speleothems depend on karst regions (light brown signature; source: https://download.bgr.de/bgr/grundwasser/whymap/shp/WHYMAP_WOKAM_v1.zip); corals are restricted to tropical areas (dark blue signature; source: https://databasin.org/datasets/b983863c0a1a41e8839383b40ade437d/); molluscs are restricted to water bodies or archaeological sites, marine and lakes sediments originate from the respective water bodies, tree-rings depend on past forest covers and to some extent on archaeological sites (green signature: global tree ring record distribution; source: https://gis.ncdc.noaa.gov/kml/paleo_tree.kmz, last data access: 06th June 2025), palaeontological and bioarchaeological samples have a global extent but depend on past human activities, excavated sites and preservation conditions. The spatial scale reflected by each proxy goes from the local to the global scale, but even local proxies may inform about supra-regional processes when considered altogether. These characteristics are summarised in Supplementary Table 1. Figure © Michael Kempf 2025.