PAGES Magazine articles

Joëlle Gergis1, P. Grierson2, A. Lorrey3, J. Palmer4 and S.J. Phipps5

1School of Earth Sciences, University of Melbourne, Australia; jgergisunimelb.edu.au

2School of Plant Biology, University of Western Australia, Australia

3National Institute of Water and Atmospheric Research, Auckland, New Zealand

4Gondwana Tree-ring Laboratory, New Zealand

5Climate Change Research Centre, University of New South Wales, Australia

Meeting of the PAGES Aus2k Working Group - Perth, Australia, 27–29 April 2011

The goals of the 2nd Australasia2k (Aus2k) workshop were to discuss the feasibility of producing an Australasian-wide temperature reconstruction, and identify a series of sub-regional studies to form a special Aus2k issue of Journal of Climate.

The Vice-Chancellor of the University of Western Australia, Professor Alan Robson, opened the workshop highlighting the importance of understanding natural climate variability. The two sessions on the first day were an open symposium devoted to showcasing state-of-the-art research developments in each of the main high-resolution Australasian paleoarchives.

Ed Cook provided an overview of the three multi-millennial tree ring chronologies from Australia and New Zealand. He was followed by Janice Lough who reviewed the suite of Great Barrier Reef coral records and promising new work from the North West Australian coast into the Indian Ocean. Tas van Ommen then outlined the utility of using the eastern Antarctic Law Dome ice core to infer changes in Southern Ocean circulation and precipitation anomalies in southwestern Australia.

Around 120 paleoclimatologists, hydrologists, ecologists, oceanographers, agricultural scientists and various natural resources managers attended the symposium resulting in energized discussions during the sessions and the deliciously-catered breaks.

The afternoon session was the start of the closed program for the core Aus2k group to discuss the issues associated with observational and proxy-climate data. Ed Cook reminded the group of the importance of replication wherever possible and the implications of using misdated series to infer high frequency climate variations.

Meteorologist Ailie Gallant then outlined the potential and limitations of using observational gridded datasets available in Australasia. We learned that the high spatial coherence of temperature over Australia (which takes up the majority of the Australasian domain) means that less than ten observational stations can capture over 80% of variance in mean temperature over the region, providing they are randomly and evenly distributed. This is perhaps unsurprising given that continental Australia is predominately a very flat, arid continent.

Figure 1: Spatial field correlation of the Cullen and Grierson (2009) Western Australian Callitris columellaris tree-ring record with the Australian Bureau of Meteorology 0.05° x 0.05° (5 x 5 km) Australian Water Availability Project (AWAP) temperature grid for winter half year (June–November) temperature (right) and rainfall (left). Correlations calculated over the 1911–2005 period. Green circle indicates location of tree-ring record.

The rest of the day was spent discussing how we reassess the climate sensitivity of the existing Australian database, perhaps exploiting the clear co-variations observed between rainfall and temperature in many part of the region. This involved examining a series of spatial field correlation maps for the records identified through the compilation of the Aus2k metadatabase (see example in Fig. 1).

Day 2 of the workshop focused on a range of relevant multi proxy analyses that have been published for North America, Asia, South America, Europe (Cook et al., 2004; Cook et al., 2010; Neukom et al., 2010a; Neukom et al., 2010b) or are currently in development, to achieve the Regional 2k Network’s objectives (Australia, New Zealand and the Southern Hemisphere).

The group was shown a preliminary 500-year annually resolved summer temperature reconstruction that has been developed by Joelle Gergis and others at the University of Melbourne. The group discussed the issue of proxy selection and the feasibility of developing a continuous, non-geographically biased temperature reconstruction spanning the past millennium. We will now move forward with refinements generated by the group to produce an Aus2k temperature paper to provide our regional contribution to a broader Regional 2k Consortium paper.

In recognition of the fact that most of Australasia’s paleoclimate records is comprised of decadal to multi-decadal sedimentary records, Scott Mooney gave an overview of the availability of the Australian material that spans the last 2000 years. Andrew Lorrey also illustrated a synoptic pressure reconstruction approach using speleothems and low resolution data. These reconstructions will form an important means of independently supporting low frequency trends and variability identified from the high-resolution material.

To round off the second day of presentations, Steven Phipps provided a thought-provoking discussion of the role of modeling in understanding the climate of the last 2000 years. He provided an example of evaluating the stability of regional teleconnections and influence of different climate forcings using simulations from the CSIRO Mk3L model.

The workshop wrapped up on a very productive note with the development of a proposed list of 15 papers for consideration in the Journal of Climate Aus2k special issue, and a clear direction forward to deliver Australasia’s best available science for the Regional 2k global synthesis.

acknowledgements

The meeting organizers would like to thank PAGES, Rio Tinto Iron Ore, the Australian Department of Climate Change and Energy Efficiency and the University of Western Australia.

references

Cook, E., Woodhouse, C., Eakin, M., Meko, D. and Stahle, D., 2004: Long-Term Aridity Changes in the Western United States, Science 306: 1015-1018

Cook, E.R., Anchukaitis, K.J., Buckley, B.M., D'Arrigo, R.D., Jacoby, G.C. and Wright, W.E., 2010: Asian Monsoon Failure and Megadrought During the Last Millennium, Science 328(5977): 486-489

Cullen, L. and Grierson, P., 2009: Multi-decadal scale variability in autumn-winter rainfall in south-western Australia since 1655 AD as reconstructed from tree rings of Callitris columellaris, Climate Dynamics 33(2-3): 433-444

Neukom, R., et al., 2010a: Multi-centennial summer and winter precipitation variability in southern South America, Geophysical Research Letters 37: doi: 10.1029/2010GL043680

Neukom, R., et al., 2010b: Multiproxy summer and winter surface air temperature field reconstructions for southern South America covering the past centuries, Climate Dynamics, doi:10.1007/s00382-010-0793-3

Jürg Luterbacher1, D. McCarroll2, D. Fleitmann3, F.J. Gonzalez-Rouco4, E. Zorita5, S. Salcedo6 and B. Vinther7

1Department of Geography, Justus Liebig University of Giessen, Germany; juerg.luterbachergeogr.uni-giessen.de

2School of the Environment and Society, Swansea University, Wales, UK

3Oeschger Centre for Climate Change Research and Institute of Geological Sciences, University of Bern, Switzerland

4Department of Astrophysics and Atmospheric Sciences, Complutense University-IGEO, Madrid, Spain

5Helmholtz Centre for Materials and Coastal Research, Germany

6Superior Polytechnic School, University of Alcalá, Madrid, Spain

7Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Denmark

Alcalá de Henares, Spain, 22-24 November 2010

Henry F. Diaz1, E.R. Wahl2 and D.S. Kaufman3

1University of Colorado, Cooperative Institute for Research in Environmental Sciences, Boulder, USA; Henry.F.Diaznoaa.gov

2National Oceanic and Atmospheric Administration/National Climatic Data Center, Boulder, USA

3Northern Arizona University, Flagstaff, USA

1st PAGES North America-2k Workshop, Flagstaff, USA, 8–10 May 2011

The principal goal of the North America 2k (NAm2k) Working Group (WG) is to synthesize high-resolution, proxy-based climate reconstructions for North America for the past 2000 years. The motivation is to enhance our understanding of the patterns of natural variability of climate in North America and possible forcing mechanisms, and for comparison with high-resolution Earth System Models.

We assembled a group of climate and paleoclimate experts (see www.pages.unibe.ch/workinggroups/namerica2k for details of members) to provide an initial assessment of our capacity to carry out the task of producing a high-resolution reconstruction of key North American climate variables with at least a decadal resolution. The WG considered the following:

- Identification of the key paleoclimate time series available for analysis.

- Evaluation of available spatiotemporal reconstructions of the key regional climatic parameters (surface air temperature and precipitation) and reconstructions of large-scale circulation modes (e.g., AMO, PDO, ENSO).

- Validation of reconstructions through statistical methods and comparison with existing hemispheric- to global-scale multiproxy based reconstructions and climate model simulations.

The following are the major findings and action items from this workshop:

Figure 1: Central Mexico June Palmer Drought Severity Index (PDSI) correlated across North America, 1950-2003 A) Reconstructed from tree rings, B) Observed. Figure from Stahle et al. (Climate Dynamics, in review), courtesy of Dave Stahle.

1) By far the most numerous climate proxy records for North America are tree-ring data (see e.g., Fig. 1), which are available at annual or better resolution over much of the continent. These records are sensitive to both temperature and precipitation variability. There is an extensive amount of peer-reviewed literature from more than 50 years of climatic reconstruction work that can be used for the NAm2k effort. The North America Drought Atlas (Cook et al. 2004) is currently the most extensive, high-temporal resolution paleoclimate record available for North America. It consists of gridded summer (JJA) Palmer Drought Severity Index values for the past 500–2000 years, with a trend towards longer records in western North America compared to eastern areas.

2) Other proxy records from lakes (e.g., isotopes, varves, chironomids, pollen, charcoal) are available for a number of sub-continental areas, and speleothem proxy records of precipitation are available for selected areas, such as the US Southwest. These records will generally reflect climate drivers for at least the last 2000 years, but with lower temporal resolution (generally) and with more limited spatial coverage than tree ring records. It was agreed that the temporal resolution of the proxy records needed for this activity would be on the order of at least 50 years, with minimum record lengths of 500 years.

3) A first step will be to develop an integrated inventory and archive of paleoclimate records for possible use in the NAm2k climate reconstruction. The goal is also to integrate the available data sets and reconstruction fields with those of the Arctic2k WG. A recommendation was made for the NOAA World Data Center for Paleoclimatology in Boulder, Colorado to become the central repository of data sets used in the NAm2k effort. The metadata could be mirrored with the PAGES 2k metadata archive on the PAGES website section for NAm2k.

4) A sub-working group composed of Scott Anderson, Henry Diaz, Darrell Kaufman, Brian Luckman, Dave Meko, Greg Pedersen, Dave Stahle, Valerie Trouet, Andre Viau and Gene Wahl will work toward the goal of assimilating (blending) the different input data sources and exploring mapping tools.

An analysis and synthesis workshop for the tree-ring chapter of the NAm2k Working Group is being organized, tentatively titled “North American Dendroclimatic Data: Compilation, Characterization, and Spatiotemporal Analysis” led by Valerie Trouet.

references

Cook, E.R., Woodhouse, C.A., Eakin, C.M., Meko, D.M. and Stahle, D.W., 2004: Long-term aridity changes in the western United States, Science 306: 1015-1018

Stahle, D.W., Burnette, D.J., Villanueva Diaz, J., Heim, R.R., Jr., Fye, F.K., Cerano Paredes, J., Acuna Soto, R. and Cleaveland, M.K., 2011: Pacific and Atlantic influences on Mesoamerican climate over the past millennium, Climate Dynamics 39(6): 1431–1446

Edward Cook1, M.P. Tingley2, E. Wahl3 and E. Zorita4

1Lamont-Doherty Earth Observatory, New York, USA; drdendroldeo.columbia.edu

2National Center for Atmospheric Research, Boulder, USA

3National Oceanic and Atmospheric Administration, National Climatic Data Center (NOAA-NCDC), Paleoclimatology Branch/World Data Center for Paleoclimatology, Boulder, USA

4Helmholtz-Zentrum Geesthacht Centre for Materials and Coastal Research, Germany

Lamont Doherty Earth Observatory of Columbia University, USA, 8-11 February 2011

Bayesian Hierarchical Models (BHMs) have emerged as a powerful new method for inferring spatially complete climate fields from sparse and noisy proxy time series. BHMs have a potential theoretical advantage over "traditional" linear subspace-based (EOF) methods for inferring climate fields, because the Bayesian "posterior" distribution of the reconstructed climate, once estimated, can be directly sampled to yield complete uncertainty estimates of the reconstructions, along with a point estimate of the expected value. The Bayesian estimates of the climate field encapsulate the uncertainties involved in the estimation of all model parameters, which cannot readily be done using traditional linear subspace methods.

A primary goal of the workshop was to bring together reconstruction experts who currently employ reduced-space multivariate regression models for climate field reconstruction, and provide an in-depth exposure to the theory and application of BHMs for climate reconstruction. Dr. Andrew Gelman of Columbia University gave the opening keynote address, and Drs. Martin Tingley of NCAR, Bo Li of Purdue University, Johannes Werner of the University of Giessen, Matthew Schofield of the University of Kentucky, and Naresh Devineni of Columbia University led the workshop with regard to the use and implementation of BHMs for spatially explicit climate reconstruction.

Figure 1: Results of a pseudo-proxy reconstruction experiment comparing Bayesian estimates from BARCAST (upper row; Tingley and Huybers, 2010) with frequentist estimates from RegEM (lower row; Schneider, 2001), an important "state-of-the-art" approach to climate field reconstruction. The left column shows point estimates of the temperature field, while the right column gives the width of 90% uncertainty estimates and indicates the locations of the pseudo-proxies. Results are for the year 1890 of the “medium” experiment described in Tingley and Huybers (2010). The additional assumptions made by BARCAST allow for spatially complete inference, while RegEM does not provide inference at locations where there are no instrumental observations during the calibration interval (indicated by the green shading)

A second important purpose of the workshop was to explore how the more established multivariate regression based methods performed in comparison to BHMs, and to examine the extent to which the traditional methods could offer equally or near-equally valid ways to characterize reconstruction uncertainties in practice (see Fig. 1). This latter goal is important due to the additional complexity and computational expense of BHM approaches, and the more formal and complete treatment of uncertainties afforded by BHMs.

A strong focus was also put on separating model building, per se, from inference of model parameters. It was noted that climate scientists sometimes mix these two concepts, which can result in significant attention being paid to inference issues and comparisons of performance within a closely-related set of models (such as "flavors" of regression, cf., Bürger et al., 2006), rather than to the more general issue of developing conceptually appropriate yet computationally tractable models. In this regard, the key shift in thinking is not to Bayesian methods but to models—which would likely be hierarchical in nature. Inference can then be conducted using a range of tools, but as models become more involved, Bayesian inference strategies may be the (conceptually) simplest option.

Several presenters stressed that BHMs are not “one size fits all”. A given model, such as BARCAST (Tingley and Huybers, 2010), may be appropriate for inferring a particular target process from a particular data set, in the sense that all diagnostics indicate the modeling assumptions are suitable, the Markov Chain Monte Carlo (MCMC) estimation process converges, and the resulting ensemble of draws has reasonable properties. However, the same model may produce results that are physically unreasonable or otherwise problematic if applied to a different data set, or used to infer a different target process examples of which were presented and discussed in the workshop. Such results can often be interpreted as an indication of model misspecification, and it was stressed that model building is an iterative process. Akin to the residual analysis that follows standard linear regression, BHMs allow for posterior checks of the suitability of the model assumptions for the data under analysis.

Bayesian Hierarchical Modeling is still in its infancy in the context of paleoclimate field reconstructions. A key goal of this workshop was to develop a common language, and to focus on formalizing scientific understanding through collaboration between paleoclimate scientists and statisticians. This first (and hopefully not last) workshop took significant steps towards enabling this necessary collaboration to proceed.

references

Bürger, G., Fast, I. and Cubasch, U., 2006: Climate reconstruction by regression-32 variations on a theme, Tellus 58A: 227-235

Schneider, T., 2001: Analysis of Incomplete Climate Data: Estimation of Mean Values and Covariance Matrices and Imputation of Missing Values, Journal of Climate 14(5): 853-871

Tingley, M.P. and Huybers, P., 2010: A Bayesian Algorithm for Reconstructing Climate Anomalies in Space and Time, Part I: Development and Applications to Paleoclimate Reconstruction Problems, Journal of Climate 23: 2759-2781

Zhengyu Liu1, B. Otto-Bliesner2 and P. Clark3

1Department of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, USA; zliu3wisc.edu

2Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, USA

3Department of Geosciences, Oregon State University, Corvallis, USA

Mount Hood, Oregon, 10-13 October 2010

Figure 1: SynTraCE-21 meeting participants in the foreground, Mount Hood in the background.

Climate reconstructions covering the last 21 ka provide critical observational data for testing state-of-the-art climate models for the simulation of climate evolution and abrupt climate changes. New proxy evidences and modeling activities have led to rapid advances in our understanding of climate change for this period. Therefore, a new PAGES Working Group, SynTraCE-21, was initiated in 2009 to synthesize the transient climate evolution of the last 21 ka. The overarching goals of the Working Group and the associated workshop series are (i) to facilitate an international synthesis effort of proxy climate records to better describe the major features of global climate during the last 21 ka, and (ii) to compare these data to transient model simulations. The first international SynTraCE-21k workshop was supported by PAGES, NOAA, and the US Department of Energy, and attracted more than 40 participants from around the world with expertise from terrestrial and marine paleoclimatology to climate modeling.

The first day began with a review of two previously held pilot workshops, which focused on marine and terrestrial records (held in Madison August 2008, and Boulder August 2009). Following this, the focus turned to an update of the meltwater history, which is the most uncertain component of climate forcing in the last deglaciation. The rest of the day was devoted to preliminary model-data comparisons in three models, two coupled general circulation models (CCSM3 and HadCM3) and a climate model of intermediate complexity (ECBilt). These transient simulations mark a new era beyond the “snapshot” studies on “time-slice” climate in paleoclimate model-data comparison because they allow for a direct comparison of time series between the model and data. The studies presented ranged from the evolution of monsoons and global surface climate to regional abyssal circulation variability, showing the great potential of these transient simulations for model-data comparison.

Transient simulations provide an unprecedented opportunity to the paleoclimatology community for model-data comparison and for improved understanding of climate evolution and abrupt climate change. As a result, it has become critical to develop a major data synthesis to better characterize the global climate variability and to compare with the new generation of transient model simulations.

The second day focused on the terrestrial proxies, with synthesis discussions of lake sediment records, including pollen and charcoal data, ice cores and speleothems. A special session was also arranged to discuss several model-data comparison strategies, including both forward and inverse modeling. The third day was devoted to marine proxies. Reconstructions of the character of the deep and intermediate waters with sedimentary isotopes studies were described. Finally, surface ocean proxies for sea surface temperature and salinity were discussed. Each day ended with an open discussion on the major topics of the day.

The presentations on each major proxy provided a great learning opportunity to all the participants, greatly promoting the interdisciplinary approach towards a multi-proxy data synthesis. To examine model robustness, the meeting participants also recommended coordinated modeling activities among the different research groups. To better assess model-model differences and climate sensitivities to external forcing, notably to meltwater forcing, while allowing for flexibility for such long simulations, one strategy proposed was to design common standard sensitivity experiments for different models. Finally, given the large amount of model data, a coordinated model data distribution was also discussed. The workshop participants agreed that the next meeting would be held in the summer of 2012. This workshop will focus on several key topics using an interdisciplinary synthesis approach. Notably, the topics will include the meltwater history and sea level reconstructions for the deglaciation, climate and terrestrial ecosystem in the North American region, and tropical hydrology.

Jerry F. McManus1, D. Raynaud2 and P.C. Tzedakis3

1Lamont-Doherty Earth Observatory of Columbia University, New York, USA
2Laboratory of Glaciology and Geophysical Environment (LGGE), Grenoble, France
3Department of Geography, University College London, UK; p.c.tzedakisucl.ac.uk

Palisades, New York, USA, 20-22 October 2010

Uncertainties related to climate variability in a warming world lend high priority to studies of warm periods in the past. The interglacial intervals of the last 800 ka serve as particularly appropriate targets for such investigations (Tzedakis et al., 2009), as they represent the culmination of warming over a range of partially ice-free global climates. In order to help focus and coordinate international efforts to study these intervals, the PAGES Working Group on Past Interglacials (PIGS) held the third in a series of workshops at the Lamont-Doherty Earth Observatory of Columbia University.

Figure 1: Examples of interglacial duration in an isotopic record from EPICA Dome C (Jouzel et al, 2007). For this illustration, the onset of interglacial warmth in Antarctica is defined by a threshold at -403 per mil in δD (Wolff et al., 2004). By this metric, past interglacial intervals lasted ~5,000 years and ~30,000 years, while the Holocene duration is now approaching 12,000 years.

Previous workshops laid out the PIGS themes and addressed intra-interglacial variability and interglacial onset. The meeting in New York brought together 30 scientists representing the marine, terrestrial, ice core and modeling communities to focus on interglacial duration (Fig. 1) and glacial inception. Participants came from 12 countries and included five postdoctoral investigators and five students.

The first day included a survey of interglacial duration based on different archives and climatic proxies. After an overview of insolation variations through time, a series of presentations reviewed the timing and duration of interglacials as viewed in climate records from ice cores, deep-sea sediments and terrestrial sequences. Presentations on ice cores focused on new chronologies, ultra-high resolution analyses, and the potential influence of atmospheric CO2 concentrations on interglacial length. Several speakers then discussed the timing and duration of sea level high-stands as seen in deep-sea sediment and absolutely dated coral records. After a presentation on the interglacial hydrological cycle recorded in speleothem records, the day concluded with a poster session and group discussion of the session themes.

The second day featured presentations of data and modeling studies of glacial inception. These included ice core results from Greenland and Antarctica, and data from different interglacials and glacial inceptions in deep-sea cores from around the globe. A session on climate modeling included presentations on the influence of atmospheric CO2 concentrations and ocean circulation on the end of an interglacial, as well as attempts to incorporate the carbon cycle in climate modeling of the last interglacial and glacial inception. The day concluded with a discussion of the session themes and review of the Working Group progress.

The final day of the meeting centered on open discussions of issues related to the two primary topics. Although the participants noted that estimates and subsequent comparisons of interglacial durations are sensitive to the definition of interglacial conditions in each proxy and archive, and that the duration of any individual interglacial may vary in different proxies and different locations, they agreed that there are nevertheless valid and robust patterns that emerge among respective interglacials. Different intervals may be defined as short if they last no more than a few thousand years, intermediate if they last approximately ten thousand years, and long if their duration is tens of thousands of years. Similarly, the respective interglacials may be compared using various climatic indicators referenced to the Holocene and defined as short or long depending on that relationship. A subset of the Working Group was therefore assigned to lead and compare differences in the duration of past interglacials in a joint publication. The physics and forcing of the climate system that lead to those differences can then be explored in a more targeted way.

In contrast to interglacial durations, which may be estimated for any number of interglacials in a single long record and may differ among locations and climate indicators, the sequence of events associated with glacial inception should be globally coherent, and is best determined using multiple climate records from different locations and archives for a single interval. In this case, Working Group members agreed that a useful approach would be to summarize the global sequence of events that accompanied the last glacial inception, and a smaller group was assigned to lead the task of preparing a joint publication on this topic. This will allow gaps to be identified and addressed, and would provide a target for comparison with subsequent compilations of previous glacial inceptions. Improved absolute and relative chronological constraints are crucial to the successful evaluation of both interglacial duration and glacial inception, and so chronology was taken up as a third focal point to emerge from the workshop.

A fourth workshop, to be hosted by Chronis Tzedakis, will be held in the UK in July 2012. This meeting will focus on efforts to explain the structure of interglacials from the forcing, and will attempt to synthesize the various aspects of past interglacials addressed by the PIGS Working Group.

references

Jouzel, J., et al., 2007: Orbital and Millennial Antarctic Climate Variability over the Past 800,000 Years, Science 317: 793-796

Tzedakis, P.C., Raynaud, D., McManus, J.F., Berger, A., Brovkin, V. and Kiefer, T., 2009: Interglacial diversity, Nature Geoscience, doi: 10.1038/ngeo660

Wolff, E. and EPICA community members, 2004: Eight glacial cycles from an Antarctic ice core, Nature 429: 623-628

Wojciech Tylmann1 and Bernd Zolitschka2

1Department of Geomorphology and Quaternary Geology, University of Gdansk, Poland; geowtug.edu.pl

2GEOPOLAR, University of Bremen, Germany

NORPOLAR Workshop, Gdańsk, Poland, 3-8 September 2010

Figure 1: Locations of NORPOLAR lake sites and participants of the NORPOLAR Workshop in front of the Faculty of Social Sciences building at Gdańsk University

The project “Northern Polish Lake Research” (NORPOLAR) is a Polish-German joint research program based on a bilateral cooperation between the Department of Geomorphology and Quaternary Geology (Institute of Geography, University of Gdańsk) and GEOPOLAR (Institute of Geography, University of Bremen). In this framework, interdisciplinary research on annually laminated sediments at four lake sites in Northern Poland has been carried out, aiming at: (1) establishing absolute and multiple-dated chronologies for all four records, (2) linking paleodata with instrumental and monitoring data to improve our understanding of pathways from forcing factors via processes to proxy records, (3) providing high-resolution data sets of paleoredox conditions, paleoproductivity, lake water balance, lacustrine carbon cycling and soil erosion, and (4) providing regional data sets of reconstructed climate parameters to be used in combination with the output of downscaled or regional climate models.

Within NORPOLAR we also address one of the major aims of the former ESF-funded European Lake Drilling Programme (ELDP), i.e., to analyze past climate and environmental variability along transects throughout Europe. The NORPOLAR lakes are located along a W-E transect covering the entire latitudinal extension of Poland from 15 to 23°E (Fig. 1) with a distinct maritime to continental climatic trend, i.e., a decrease in mean annual temperature from 8.5 to 6.0°C from West to East.

The NORPOLAR Workshop was organized by Wojciech Tylmann and Małgorzata Kinder. It teamed 23 participants from Poland, Germany and Switzerland (Fig. 1). The aims of this workshop were twofold: (1) To familiarize all project participants with the up-to-date state of scientific results, and (2) To develop a strategy for future research activities. The workshop included invited lectures, oral presentations by all project members and a forum for discussion. Five oral sessions were organized during two days of intense work. The first day was devoted to a general introduction, the lithology of varved sediment records and dating issues, while the second day focused on biological proxies.

We started with excellent talks on the nature of varves and the current state of seasonal climate reconstruction from varved sediments presented by Achim Brauer (German Research Centre for Geosciences, Potsdam) and Christian Kamenik (University of Bern, Switzerland), respectively. The following talks explained the general idea of the project, reported on fieldwork, core correlation as well as on sub-sampling strategies, and shed some light on issues related to chronological and geochemical data interpretation. During the second day three sessions dealt with pollen, diatom and cladocera analyses of the varved sediment records from four sites studied so far within NORPOLAR (Fig. 1).

The final discussion addressed future NORPOLAR research strategies. There was general consensus on the high potential of these sediment records, especially for high-resolution reconstructions of climatic and environmental variations during the last 3 ka but also back to the early Holocene. Based on personal links established during the 1st PAGES Varves Working Group Workshop (see: PAGES news, vol. 18(2)), NORPOLAR grew to become a trilateral research project, now also involving Swiss scientists from the University of Bern.

The workshop ended with two field trips taking workshop participants to the largest active dune field in Europe (Słowiński National Park), to the Gdańsk University Marine Station on Hel peninsula, and to the cliff at Jastrzębia Góra, one of the few outcrops in Northern Poland with exposed Miocene clays and silts covered by Quaternary glacial sediments. Here the observing eyes of the varvologists (Quaternary scientists working with varved sediments) recognized glacial varves in a small section that has most likely been relocated as a frozen block by the glacier. These two days filled with plenty of atmosphere were great for continuative and in-depth scientific discussions related to NORPOLAR.

NORPOLAR was jointly sponsored by the Polish Ministry of Science and Higher Education and the German Research Foundation (DFG). More information about NORPOLAR is available at www.norpolar.ug.edu.pl.

Andreas Schmittner1, A. Abe-Ouchi2, P. Braconnot3, S.P. Harrison4 and B.L. Otto-Bliesner5

1College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, USA: aschmittcoas.oregonstate.edu

2Atmosphere and Ocean Research Institute, University of Tokyo, Japan

3Laboratory for Climate and Environmental Sciences, Gif-sur-Yvette, France

4Macquarie University, Sydney, Australia

5Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, USA

Kyoto, Japan, 6-10 December 2010

Past changes in Earth’s climate, as evidenced by a myriad of paleo-environmental records, inform our understanding of the coupled climate system and can be used to evaluate models used for future projections. The Paleoclimate Modelling Intercomparison Project (PMIP; endorsed by WCRP, PAGES and INQUA/PALCOMM; Joussaume and Taylor, 1995) has taken on the important task of organizing and facilitating a systematic comparison of past climate simulations from different models and paleodata. This involves the definition of common experimental designs, running experiments for key time periods, and syntheses of data sets. Building on its successful work since the 1990s, PMIP, now in its third phase (PMIP3; Otto-Bliesner et al., 2009), remains close to future climate investigation, and has opened new research frontiers through investigation of additional time periods and transient simulations. More than 100 scientists from around the world contributed to this vibrant community effort at the recent workshop sponsored by the Japan Society of Promoting Science, the University of Tokyo and the Japan Agency for Marine-Earth Science and Technology.

PMIP3 continues work on the Last Glacial Maximum (LGM, 21 ka ago) and the mid-Holocene (6 ka ago), and has begun work on the Last Millennium. These key time periods are now recommended as high priority (Tier 1 and 2) simulations in the Coupled Model Intercomparison Project Phase 5 (CMIP5; Taylor et al., 2009) using the same models that will be used for projections of future climate for the upcoming 5th Assessment Report of the Intergovernmental Panel on Climate Change. This is a new and exciting development because paleoclimate simulations were previously done with different models—typically coarser resolution—from those used for future simulations, interrupting the direct link between past and future. PMIP will also be assessing carbon-cycle modeling, through its daughter project PCMIP (PalaeoCarbon Modelling Intercomparison Project; Abe-Ouchi and Harrison, 2009), focusing on simulations of the LGM and the Last Millennium.

Figure 1: Reconstructions of northern hemisphere ice sheets (contour lines show 500 m elevation differences, available at http://pmip3.lsce.ipsl.fr) and surface temperature differences from modern (color scale in K) for the Last Glacial Maximum. Sea surface temperatures are from the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface project (MARGO; Waelbroeck et al., 2009), land surface air temperature reconstructions are based on pollen (Bartlein et al., 2010), with additional data from Shakun et al. (in preparation). These data, in combination with model simulations, provide unique constraints on climate sensitivity, confidently excluding high values (> 4.5 K per doubling of CO2) (Hargreaves et al. 2011, Schmittner et al., Yoshimori et al., submitted).

A new ice sheet reconstruction (Fig. 1) is being used for the LGM simulations, which blends together several recent model-based reconstructions (Abe-Ouchi et al., unpublished). Recent syntheses of surface temperatures from oceans and land and other data (Fig. 1) are being used to provide important constraints on models’ climate sensitivity, polar amplification, ocean versus land response, the hydrological cycle and interannual to multi-decadal variability. These and other data sets, such as vegetation distribution, fire regimes and peatland carbon accumulation, will be made available via the PMIP3 web site (http://pmip3.lsce.ipsl.fr). Missing data sets or ones that will require additional work in the coming year were identified at the Kyoto meeting, the most vital of these being a synthesis of short-term (interannual to interdecadal) climate variability during the LGM, the mid-Holocene and the last millennium. The PAGES 2k initiative (http://www.pages.unibe.ch/workinggroups/2k-network) is expected to take the lead on the last-millennium synthesis. Compilations of deep-sea data, such as carbon isotopes for the LGM, are also planned and will provide constraints on modeled ocean circulation and carbon cycle.

CMIP5 simulations are not the only focus in PMIP. New in the set of PMIP experiments are warm periods such as the Pliocene, the Eocene, the Last Interglacial and transient simulations of the Holocene and the Last Interglacial, which have obvious relevance to a future warmer world. Another new focus is on transient simulations of the last deglaciation and freshwater hosing experiments, such as the 8.2 ka event and Heinrich event H1. These experiments and model-data comparisons will provide new estimates of forcing thresholds that influence polar amplification, the low-latitude hydrologic cycle, and the relationship between ice sheets and sea level under different climate states. The transient experiments represent an important step towards a better understanding of the dynamics and temporal response of the different components of the climate system.

In the next two years, PMIP will be sponsoring a series of small workshops, including ones focusing on the compilation of new data sets, on the last-millennium carbon cycle (PCMIP), on benchmarking the CMIP5 simulations, and on data-model comparisons for the Pliocene (PlioMIP). In addition, PMIP will continue to hold annual meetings bringing the paleoclimate modeling community together to discuss progress on all of the PMIP foci.

references

Bartlein, P., et al., 2010: Pollen-based continental climate reconstructions at 6 and 21 ka: a global synthesis, Climate Dynamics, doi: 10.1007/s00382-010-0904-1

Hargreaves, J.C., Paul, A., Ohgaito, R., Abe-Ouchi, A. and Annan, J.D, 2011: Are the paleomodel ensembles consistent with the MARGO data synthesis? Climate of the Past Discussion 7: 775-807

Otto-Bliesner, B.L., Joussaume, S., Braconnot, P., Harrison, S.P. and Abe-Ouchi, A., 2009: Modeling and data synthesis of past climates, Eos 11: 93

Schmittner, A., Bartlein, P.J., Clark, P.U., Mahowald, N.M., Rosell-Melé, A. and Shakun, J.D., submitted: Climate sensitivity estimated from temperature reconstructions of the Last Glacial Maximum, Science

Waelbroeck, C., et al., 2009: Constraints on the magnitude and patterns of ocean cooling at the Last Glacial Maximum, Nature Geoscience 2(2): 127-132

For full references please consult: http://pastglobalchanges.org/products/newsletters/ref2011_2.pdf

Alfred Muzuka

The Nelson Mandela African Institute of Science and Technology, Arusha, Tanzania; annmuzukayahoo.co.in

Zanzibar, Tanzania, 7-12 February 2011

Figure 1: EAQUA meeting participants

The workshop was hosted by the Institute of Marine Sciences of the University of Dar es Salaam. It was attended by 55 participants (Fig. 1) from 17 countries and received coverage in local media including Radio television Zanzibar and newspapers. The workshop was generously supported by the Directorate of Research of the University of Dar es Salaam, INQUA, Paleontological Scientific Trust (PAST), and Past Global Changes (PAGES).

The official opening was attended by the Permanent Secretary of the Ministry of State in the President's Office Public Services and Good Governance, Mr. Joseph Meza on behalf of the Minister Hon. Haji Omar Kheri. The workshop was officially concluded by the Director of Records and Archive Mr. Hamad Omar.

Mr. Meza underscored the importance of EAQUA as a regional body that fosters Quaternary Science research in East Africa. He pointed out that the treasures of the rich archeological and anthropological history of Eastern and Central Africa has not yet been fully unearthed owing to a lack of capacity and resources, thus requiring multidisciplinary cooperation and capacity development. Such treasures could help to fight poverty through promotion of ecotourism. He also reminded participants to reflect on how far EAQUA has achieved its mission of enhancing growth of the Quaternary science community in the region through training, collaborative research and information exchange. Participants were urged to come up with tangible results, such as student exchange programs and joint proposals. He challenged the Institute of Marine Sciences of the University of Dar es Salaam to develop a postgraduate program in maritime archeology, which could boost archeological studies in the entire Great Lakes Region.

The EAQUA workshop was preceded by a one day INQUA/EAQUA meeting with presentations from INQUA, Pan African START Secretariat (PASS) and EAQUA country representatives. INQUA presented objectives, activities and available opportunities for the EAQUA members to participate in the programs of the commissions. PASS presented opportunities to the members for training and research, for example, the African Climate Change Fellowship Program (ACCFP) and the Education Program on Climate Change and Biodiversity Conservation. Participants were urged to take a leading role in utilizing these opportunities. Country representatives reported on Quaternary research activities in the region and felt that more capacity building is required.

The general theme of the 3rd EAQUA workshop was “On- and off-shore: Eastern Africa during the last 100 ka”. The workshop had 40 oral and 5 poster presentations. Talks were divided into six sessions namely (i) Marine and lacustrine records and reconstruction, (ii) Techniques and methodological development in Quaternary research, (iii) Paleoclimate reconstruction, (iv) Vegetation reconstruction (v) Recent trends in climate change-Impacts and vulnerability assessment for eastern Africa, and (vi) Trade, anthropology and archeological studies in Eastern Africa. Time was also allocated for a roundtable discussion where several priority areas of research were identified: (i) Compilation of modern archives of climatic records for the last millennia, (ii) Reconnaissance program to establish caves hosting speleothems, (iii) Creation of a database of Quaternary scientists and projects working in eastern Africa; (iv) Archeology, environment and Humans focusing on issues such as hydrology, vegetation, fire, human-climatic influences, and others. Additionally, the need for several focused meetings with a progressive agenda was emphasized.

The EAQUA workshop concluded with a discussion of association matters, including the election of executive members. Elected for a period of 2 years are: Prof. Mohammed Umer (President), Prof. Alfred N.N. Muzuka (Vice President), Ms Christine Ogolla (Secretary General), Ms Jackline Nyiracyiza (Treasurer), Prof. Asfawossen Asrat (News Letter Editor), Dr. Immaculate Ssemmanda (National Representative (NR Uganda), Ms. Rahab Kinyanjui (NR Kenya), Elgidius Ichumbaki (NR Tanzania), Dr. Julius Lejju (Ex-Officio), Dr. Margareth Avery (INQUA).

Jorge Sánchez-Sesma1 and Arthur Miller2

1Mexican Institute of Water Technology, Jiutepec, Mexico; jsancheztlaloc.imta.mx

2Scripps Institution of Oceanography, University of California, San Diego, USA

San Diego, USA, 3-4 September 2010

ENSO is the largest signal of sub-annual climate variability in the Pacific Ocean, affecting not only coastal but also inland locations. Its torrential rains and severe droughts result in economical losses of several hundred millions of dollars in affected countries, from the USA and Mexico to southern South America and as far as Australia. The increase of ENSO frequency and intensities during the second part of the 20th century has affected various sectors, from agriculture to health, from fisheries to the economy. Thus understanding, and ultimately forecasting ENSO variability, has an enormous potential societal benefit.