{
 "updated": "2026-10-17",
 "note": "Evidence cards for the Climate tab. 'measured' is what the laboratory or field actually measured; 'inferred' is the environmental condition the authors reconstruct from it. Summaries are this site's own wording; consult the original paper before citing.",
 "studies": [
  {
   "id": "smith2024-orangutan",
   "title": "Oxygen isotopes in orangutan teeth reveal recent and ancient climate variation",
   "citation": "Smith, T. M. et al. (2024). eLife 12: RP90217.",
   "doi": "10.7554/eLife.90217",
   "url": "https://elifesciences.org/articles/90217",
   "published": "2024-03-08",
   "archive": "Biological archive: museum and cave-fossil teeth",
   "archive_kind": "archaeological",
   "question": "Can oxygen isotopes in orangutan tooth enamel record rainfall seasonality, and how did Pleistocene and early-Holocene conditions on Sumatra and Borneo compare with the recent past?",
   "location": "Sumatra (Lida Ajer and Sibrambang caves) and Borneo (Niah Caves); modern museum specimens from Borneo and Sumatra",
   "scope": "Local to regional (individual animals' home ranges); not a basin-wide or global signal",
   "period": "Modern specimens collected c. 1880s–1939; fossils with minimum U-series ages of about 8–9 ka (Niah), 33–40 ka (Lida Ajer) and 60–70 ka (Sibrambang)",
   "dating": "Uranium-series minimum ages for fossils (ka = thousand years before present); collection dates for museum specimens",
   "evidence": "12 molars from 6 modern orangutans (2,016 measurements) and 6 fossil molars (955 measurements)",
   "measured": "δ18O of enamel, by ion microprobe (SHRIMP SI) in ~15×20 µm spots along daily growth increments",
   "inferred": "Rainfall seasonality and relative wetness or dryness (via the isotopic composition of drinking water and food)",
   "resolution": "About weekly within each animal's tooth-forming years (roughly 3–11 years per individual)",
   "finding": "Modern Sumatran teeth show clear annual or twice-yearly cycles; Bornean teeth are less regular, with swings that may reflect El Niño years. Fossil Sumatran teeth resemble modern ones; fossil Bornean teeth from Niah are at least 2‰ heavier, which the authors read as possibly drier conditions with weaker monsoon rainfall.",
   "uncertainty": "Small sample (6 modern, 6 fossil molars); fossil ages are minimum estimates; no local rainfall-isotope measurements, so modelled precipitation isotopes were used; diet, canopy height and altitude can also shift enamel δ18O. Enamel isotopes are not a thermometer and do not give rainfall amounts directly.",
   "data": "Source data in the article's supplementary files",
   "data_url": "https://elifesciences.org/articles/90217"
  },
  {
   "id": "kielhofer2023-tanana",
   "title": "brGDGT temperature reconstruction from interior Alaska: assessing 14,000 years of deglacial to Holocene temperature variability and potential effects on early human settlement",
   "citation": "Kielhofer, J. R. et al. (2023). Quaternary Science Reviews, article 107979.",
   "doi": "10.1016/j.quascirev.2023.107979",
   "url": "https://doi.org/10.1016/j.quascirev.2023.107979",
   "published": "2023",
   "archive": "Archaeological sites: buried soils at occupation sites",
   "archive_kind": "archaeological",
   "question": "What were temperatures like when people first settled the Tanana Valley, and did temperature change drive changes in occupation?",
   "location": "Middle Tanana Valley, interior Alaska, including the Keystone Dune site",
   "scope": "Local (valley); the authors stress that it did not follow the expected global pattern",
   "period": "About 14,000 years ago to the present (deglacial to Holocene)",
   "dating": "Radiocarbon-based site chronologies (calibrated years before present); see the paper for the age model",
   "evidence": "Sediment and soil samples from archaeological sites",
   "measured": "Branched GDGTs: membrane lipids of soil bacteria, whose molecular structure varies with temperature",
   "inferred": "Mean annual air temperature",
   "resolution": "Multi-centennial to millennial: each sample integrates a soil horizon (see the paper for sample spacing)",
   "finding": "Temperatures stayed fairly stable through the record, contrary to expectations of large deglacial swings, so temperature alone does not explain changes in human occupation; relative warmth may have made the valley attractive.",
   "uncertainty": "Calibration error of about ±2.8 °C on each estimate; soils integrate long periods; brGDGT temperature relationships vary between environments; aridity was not reconstructed.",
   "data": "See the article's supplementary data",
   "data_url": "https://doi.org/10.1016/j.quascirev.2023.107979"
  },
  {
   "id": "jouzel2007-epica",
   "title": "Orbital and millennial Antarctic climate variability over the past 800,000 years",
   "citation": "Jouzel, J. et al. (2007). Science 317: 793–797.",
   "doi": "10.1126/science.1141038",
   "url": "https://www.ncei.noaa.gov/pub/data/paleo/icecore/antarctica/epica_domec/edc3deuttemp2007.txt",
   "published": "2007-08-10",
   "archive": "Natural archive: Antarctic ice core",
   "archive_kind": "natural",
   "question": "How did Antarctic temperature vary through the last eight glacial cycles?",
   "location": "EPICA Dome C, East Antarctica (75°06′S, 123°21′E)",
   "scope": "Site to regional (East Antarctic plateau), not global mean temperature",
   "period": "About 800,000 years ago to the present",
   "dating": "EDC3 age model (glaciological model with tie points); ages in years before 1950",
   "evidence": "3,259.7 m of ice, sampled in 55 cm sections (about 5,800 samples)",
   "measured": "Deuterium content of the ice (δD, ±0.5‰ analytical accuracy)",
   "inferred": "Local temperature relative to the last 1,000 years, after corrections for seawater isotopic composition and ice-sheet elevation",
   "resolution": "Decades near the top to more than a thousand years per sample near the bottom",
   "finding": "Eight glacial–interglacial cycles, with Dome C temperature ranging from about 10.6 °C below to 5.5 °C above the average of the last 1,000 years; interglacials differ in warmth, which the authors link to the interplay of Earth's orbital cycles.",
   "uncertainty": "The isotope–temperature relationship can change with moisture source and snowfall seasonality; age-model uncertainty grows with depth; a single site is not a global average.",
   "data": "NOAA/World Data Service for Paleoclimatology, contribution 2007-091",
   "data_url": "https://www.ncei.noaa.gov/pub/data/paleo/icecore/antarctica/epica_domec/edc3deuttemp2007.txt"
  },
  {
   "id": "kaufman2020-temp12k",
   "title": "Holocene global mean surface temperature, a multi-method reconstruction approach",
   "citation": "Kaufman, D. et al. (2020). Scientific Data 7: 201.",
   "doi": "10.1038/s41597-020-0530-7",
   "url": "https://www.ncei.noaa.gov/pub/data/paleo/reconstructions/kaufman2020/readme-kaufman2020gmst.txt",
   "published": "2020-06-30",
   "archive": "Multi-proxy synthesis (natural archives)",
   "archive_kind": "natural",
   "question": "How did global and latitude-band mean surface temperature change over the last 12,000 years, with realistic uncertainty?",
   "location": "Global, plus six 30° latitude bands",
   "scope": "Global and zonal means",
   "period": "12,000 years before present (1950 CE) to the 20th century",
   "dating": "Proxy chronologies from the source records; 100-year bins centred on each age",
   "evidence": "Temperature 12k Database v1.0 (lake and marine sediments, pollen, ice cores and other proxies)",
   "measured": "Many proxy types, each already calibrated to temperature in the source studies",
   "inferred": "Annual mean surface temperature anomaly relative to 1800–1900 CE",
   "resolution": "100-year bins",
   "finding": "The warmest 200-year interval was around 6,500 years ago, about 0.7 °C (0.4 to 1.8) warmer than the 19th century; temperature then cooled by about 0.08 °C per 1,000 years until the industrial era.",
   "uncertainty": "Five statistical methods × 500 ensemble members; the 5th–95th percentile range includes proxy, chronology and method uncertainty. Centennial bins cannot resolve decades, and proxies are uneven in space and season. Some studies argue the early-Holocene warmth reflects summer-biased proxies (the 'Holocene temperature conundrum').",
   "data": "NOAA/WDS-Paleo, dataset DOI 10.25921/vzys-1280",
   "data_url": "https://www.ncei.noaa.gov/pub/data/paleo/reconstructions/kaufman2020/"
  }
 ]
}