130 PAGES news • Vol 17 • No 3 • October 2009 References Elsig, J., Schmitt, J., Leuenberger, D., Schneider, R., Eyer, M., Leuenberger, M., Joos, F., Fischer, H. and Stocker, T., 2009: Stable isotope con- straints on Holocene carbon cycle changes from an Antarctic ice core, Nature, 461: 507-510. Monnin, E., Indermühle, A., Dällenbach, A., Flückiger, J., Staufer, B., Stocker, T., Raynaud, D. and Barnola, J.-M., 2001: Atmospheric CO 2 concentrations over the last glacial termination, Science, 291: 112–114. Flückiger, J., Monnin, E., Staufer, B., Schwander, Stocker, T., Chappellaz, J., Raynaud, D. and Barnola, J.-M., 2002: High-resolution Holocene N 2 O ice core record and its relationship with CH 4 and CO 2 , Global Biogeochemical Cycles, 16: 1010, doi:10.1029/2001GB001417. Towards a global synthesis of the climate of the last two millennia Workshop of the PAGES 2k Regional Network – Corvallis, USA, 7 July 2009 LOUISE NEWMAN 1 , H. WANNER 2 AND T. KIEFER 1 1 PAGES International Project Ofce, Bern, Switzerland; newman@pages.unibe.ch 2 Oeschger Centre for Climate Change Research and Institute of Geography, University of Bern, Switzerland; heinz.wanner@giub.unibe.ch Research on the last 1-2 ka has resulted in several multi-proxy reconstructions of global and hemispheric temperature, and other climatic parameters (e.g., Rutherford et al., 2005; Mann et al., 2006; 2008; Luter- bacher et al., 2004). Despite this, we still do not sufciently understand the precise sequence of changes related to regional climate forcings, internal variability, sys- tem feedbacks, and the responses of sur- face climate, land-cover, biosphere and hydrosphere. Furthermore, many parts of the globe lack adequate paleorecords for comparison with model simulations, and high-resolution instrumental datasets are sparse. To address these knowledge gaps, PAGES developed the Regional 2k Network—a set of Working Groups (WGs) that collect and process the best available time series and spatial reconstructions of important climate system variables for a given re- gion (including the adjacent ocean; Fig. 1). Several WGs built on existing projects and are, therefore, at a mature stage in their research, while other WGs have only re- cently formed. All the WGs recently came together for a one-day workshop in Cor- vallis, USA to discuss regional results, ex- change information on approaches and techniques, and develop a coordinated strategy for outcomes and syntheses. Following an introductory talk by Heinz Wanner, the state-of-the-science for each group was presented. Representing Eu- rope and the Mediterranean, Jürg Luter- bacher presented a compilation of an- nual- and lower-resolution proxy records, and highlighted eforts towards spatial re- constructions and associated uncertainty estimates for a dynamical understanding of European climate. The focus of this WG now is to push the temporal scale of spa- tial reconstructions to cover 2 ka, combin- ing all available proxies, data-model com- parison and data assimilation exercises. The North American WG is also well placed to move towards synthesis. Caspar Ammann highlighted the extensive net- work of proxy records available and out- lined new methodological advances that will provide greater understanding of the physical mechanisms behind past climatic changes. Future goals of this WG are to produce a review of the available data and to cross validate with model output. A concerted South American efort has resulted in a recently published se- ries of regional syntheses of data sets from a variety of paleoclimate archives (see details on website). Ricardo Villalba presented an overview of these results, and showed that the spatial and temporal coverage of the data is adequate to de- velop multi-proxy feld reconstructions for southern South America for the past ca. 500 years. Eforts are now being directed towards homogenizing instrumental data sets for calibration of proxy data series, and increasing their temporal and spatial coverage. The Asia 2k WG is under develop- ment. Edward Cook presented multi-proxy reconstructions of the Asian monsoon, temperature and drought from Eastern Asia, the Altay Mountains and Indochina, respectively. The next step for this group is to consolidate the team, followed by a review of the available data and gaps in knowledge. Figure 1: Recent results from the LOTRED-South America 2k efort. Climate variations in the Northern Patagonian Andes during the past four centuries. a) Summer (Nov - Mar) temperature changes (expressed as departure from calibration period 1908-2003) inferred from a regional network of Fitzroya cupressoides tree-ring chronologies in northern Patagonia (blue line; Villalba et al., 2006) plotted with the instrumental summer temperature variations for northern Patagonia (red line; Jones and Moberg, 2003) for the interval 1908-2003. The correlation coefcient observed v's reconstructed is r = 0.75 (n = 85, p< 0.01). b) Tree-ring based reconstruction of Dec-May stream fow deviations (expressed as departure from calibration period 1943-1999) of Río Puelo from 1599 to 1999 developed from a combination of Austrocedrus chilensis and Pilgerodendron uviferum chronologies (red line; Lara et al., 2008). It correlates signifcantly with the instrumental Rio Puelo stream fow recorded at Carrera Basilio, Chile (green line) for the period 1943-1999, at 99% confdence level (r = 0.65). Thick lines in both a and b represent 15-year cubic splines to emphasize low frequency variations in the reconstructions. c) Frontal variations of selected glaciers in the North Patagonian Andes. Total retreat of the glacier with the longest record (Glaciar Frías; AD 1660-2007) was normalized to -1.0 and the frontal variations of the other glaciers were adjusted to this range of variation. Glacier frontal variations are from Villalba et al., (1990), Bown and Rivera (2007), and Masiokas et al. (2008; 2009). The thin interpolation-lines in (c) are drawn to enhance the readability and do not suggest linear trends between two data points. Workshop Reports