Past global climate changes had strong regional expression. To elucidate their spatio-temporal pattern, we reconstructed past temperatures for seven continental-scale regions during the past one to two millennia. The most coherent feature in nearly all of the regional temperature reconstructions is a long-term cooling trend, which ended late in the nineteenth century. At multi-decadal to centennial scales, temperature variability shows distinctly different regional patterns, with more similarity within each hemisphere than between them. There were no globally synchronous multi-decadal warm or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age, but all reconstructions show generally cold conditions between AD 1580 and 1880, punctuated in some regions by warm decades during the eighteenth century. The transition to these colder conditions occurred earlier in the Arctic, Europe and Asia than in North America or the Southern Hemisphere regions. Recent warming reversed the long-term cooling; during the period AD 1971-2000, the area-weighted average reconstructed temperature was higher than any other time in nearly 1,400 years

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Our understanding of the impact of climate-driven environmental change on prehistoric human populations is hampered by the scarcity of continuous paleoenvironmental records in the vicinity of archaeological sites. Here we compare a continuous paleoclimatic record of the last 20 ka before present from the Chew Bahir basin, southwest Ethiopia, with the available archaeological record of human presence in the region. The correlation of this record with orbitally-driven insolation variations suggests a complex nonlinear response of the environment to climate forcing, reflected in several long-term and short-term transitions between wet and dry conditions, resulting in abrupt changes between favorable and unfavorable living conditions for humans. Correlating the archaeological record in the surrounding region of the Chew Bahir basin, presumably including montane and lake-marginal refugia for human populations, with our climate record suggests a complex interplay between humans and their environment during the last 20 ka. The result may contribute to our understanding of how a dynamic environment may have impacted the adaptation and dispersal of early humans in eastern Africa.authorsversionPeer reviewe

We combine surface and cave climate monitoring with multiple stalagmite parameters to help understand and calibrate the climate records contained within stalagmites from a region with strong rainfall seasonality.

The African continent is characterised by a wide range of hydroclimate regimes, ranging from humid equatorial West Africa to the arid deserts in the northern and southern subtropics. The livelihoods of much of its population are also vulnerable to future climate change, mainly through variability in rainfall affecting water resource availability. A growing number of data sources indicate that such hydroclimatic variability is an intrinsic component of Africa's natural environment. This paper, co-authored by members of the PAGES Africa 2k Working Group, presents an extensive assessment and discussion of proxy, historical and instrumental evidence for hydroclimatic variability across the African continent, spanning the last two millennia. While the African palaeoenvironmental record is characterised by spatially disjunctive datasets, with often less-than-optimal temporal resolution and chronological control, the available evidence allows the assessment of prominent spatial patterns of palaeomoisture variability through time. In this study, we focus sequentially on data for six major time windows: the first millennium AD, the Medieval Climate Anomaly (900-1250 CE), the Little Ice Age (1250-1750 CE), the end of the LIA (1750-1850 CE), the Early Modern Period , and the period of recent warming (1950 onwards). This results in a continentwide synthesis of regional moisture-balance trends through history, allowing consideration of possible driving mechanisms, and suggestions for future research.