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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

The increasing carbon dioxide (CO 2 ) concentration in the atmosphere in combination with climatic changes throughout the last century are likely to have had a profound effect on the physiology of trees: altering the carbon and water fluxes passing through the stomatal pores.However, the magnitude and spatial patterns of such changes in natural forests remain highly uncertain. Here, stable carbon isotope ratios from a network of 35 tree-ring sites located Central Europe, a region where summer soil-water availability decreased over the last century.We were able to demonstrate that the combined effects of increasing CO 2 and climate change leading to soil drying have resulted in an accelerated increase of iWUE. These findings will help to reduce uncertainties in the land surface schemes of global climate models, where vegetation-climate feedbacks are currently still poorly constrained by observational data. 4

Stable carbon isotope ratios from the latewood cellulose of 12 trees from two sites in northern Finland are used to construct an isotope chronology covering AD 1640 to 2002. By measuring isotopic ratios of every sample independently it is possible to identify and remove the juvenile portion of each δ 13C series, correct the individual series for anthropogenic changes in atmospheric carbon dioxide isotopic ratios and concentrations, and to quantify changes in signal strength through time. Most importantly, it is possible to demonstrate that there are no long-term trends in the carbon isotope series that are related to tree age. This means that it is not necessary to detrend the series and so they have the potential to retain climate information at all temporal frequencies. The correlation between the non-detrended carbon isotope series and July/August mean temperature is high ( r=0.72) and comparison with meteorological records suggests that the dominant control over tree ring δ13C at these high latitude, moist sites is photosynthetic rate rather than stomatal conductance. Summer temperature reconstructions based on three different calibrations are presented, with verification based on a mixture of jacknife and split period designs, providing robust and near identical results. Reconstructed late summer temperatures in the early 1900s are very low but the years centred around AD 1660 and 1760 appear to have experienced warmer summers than the late twentieth century, thus our late summer reconstruction does not show a recent warming trend. Our results are in agreement with other palaeoclimate reconstructions for northern Fennoscandia, which show late twentieth-century warming occurring predominantly in the winter. Our results suggest that, where replication and common signal strength are sufficiently high, stable carbon isotope dendroclimatology may provide high resolution proxy time series that also record climate information at lower temporal frequencies, thus avoiding the `segment length curse' that can apply to palaeoclimate reconstructions based on other tree ring parameters such as ring widths and density.

We present an 8000‐year history spanning 650 km of ice margin retreat for the largest marine‐terminating ice stream draining the former British–Irish Ice Sheet. Bayesian modelling of the geochronological data shows the ISIS expanded 34.0–25.3 ka, accelerating into the Celtic Sea to reach maximum limits 25.3–24.5 ka before a collapse with rapid marginal retreat to the northern Irish Sea Basin (ISB). This retreat was rapid and driven by climatic warming, sea‐level rise, mega‐tidal amplitudes and reactivation of meridional circulation in the North Atlantic. The retreat, though rapid, is uneven, with the stepped retreat pattern possibly a function of the passage of the ice stream between normal and adverse ice bed gradients and changing ice stream geometry. Initially, wide calving margins and adverse slopes encouraged rapid retreat (∼550 m a−1) that slowed (∼100 m a−1) at the topographic constriction and bathymetric high between southern Ireland and Wales before rates increased (∼200 m a−1) across adverse bed slopes and wider and deeper basin configuration in the northern ISB. These data point to the importance of the ice bed slope and lateral extent in predicting the longer‐term (>1000 a) patterns and rates of ice‐marginal retreat during phases of rapid collapse, which has implications for the modelling of projected rapid retreat of present‐day ice streams. Copyright © 2013 John Wiley & Sons, Ltd.