Scientific Rationale

The main aim of this COST Action is to develop common protocols and methods to reconstruct abrupt and extreme climate changes across the full range of the European environment (ice, marine and terrestrial) over the period 60,000 to 8000 years ago, to better understand the mechanisms and impact of change, and thereby reduce the uncertainty of future prediction.
Past climate and environmental data provide critical tests of global and regional climate models. While there are a small number of high profile records, such as the Greenland ice cores, which are critical for informing on the dynamic nature of past climate change, it is at the scale of Europe and the North Atlantic that abrupt climate variability needs to be fully explored. It is crucial that independent records of abrupt climate change across Europe are generated and robustly compared to test for leads/lags in the climate system and the interaction between different climate forcing mechanisms. Doing so will critically underpin our ability to model future climate change and ecosystem response. The main objectives of this Action are to standardize methodologies across Europe; incorporate reconstructions within climate models; and facilitate interdisciplinary science collaborations, including early-stage and established scientists, to build European research capacity.

General background

Since the 1960s, scientific understanding of our global environment and its climate has undergone a remarkable transformation. We are now increasingly aware that the world around us is dynamic, and quasi-stable only in the short-term. Recognizing the challenge of human-induced climate change, the World Meteorological Organization and the United Nations Environment Program established the Intergovernmental Panel on Climate Change (IPCC) in 1988 to assess our understanding of the scientific basis of the risks of climate change and opportunities for adaptation and mitigation. Since this time, the IPCC has reported a scientific consensus of the latest findings; the most recent Fourth Assessment Report (AR4) was released through 2007. The conclusions are startling: by 2100 global temperatures are estimated to increase between 1 and 6.5degC compared to 1990, accompanied by a sea level rise of 20 to 60 centimetres (IPCC, 2007). Worryingly, the AR4 estimates already appear conservative (Rahmstorf et al., 2007), largely because of increasing greenhouse gas emissions and uncertainties in the sensitivity of the Earth system to changes in radiative forcing. Palaeoclimate data can address this issue, extending historical records and providing critical insights into climate system extremes, thereby reducing uncertainty of future change (Schrag and Alley, 2004). Of particular importance is understanding changes in the climate system around so-called tipping points. To fully exploit the value of past climate and environmental change, this Action will draw upon the lessons learnt from previous initiatives and work within the period 60,000 to 8000 years ago, a period which represents exceptional climatic variability that experienced both abrupt (on annual to decadal timescales) and long-term (centennial to millennial) extremes that coincided with significant changes in atmospheric CO2 concentration (Monnin et al., 2001), deepwater formation (Marchitto et al., 2007), westerly airflow (Shulmeister et al., 2004) and sea level (Chappell 2002; Turney and Brown, 2008) that had significant impacts on past European populations (Turney et al., 2006).

This COST Action will bring together pan-European scientists and international experts to focus on developing innovative past climate reconstruction tools and methods. A key learning experience of previous activities by group members is strong incentives for a foundation of interdisciplinary and international collaboration networks are needed, in order to link the European and Non-European researchers active in this research field. According to the objectives, this Action is the most appropriate research framework to implement a past climate research network in Europe.

In line with the highlighted scientific questions and problems, the objectives of the proposed cooperation are:

1. to review and analyze the state-of-the-art in climate reconstructions from ice-core, marine, and terrestrial records;

2. to standardize the tools and methods used in climate reconstruction and development of chronological frameworks;

3. integrate pan-European climate reconstructions using common methods within highly-precise chronological frameworks;

4. determine the timing, rates of change, spatial variability and climate gradients and ecosystem impacts;

5. incorporate reconstructions into climate models to better determine the mechanisms of regional and global change; and

6. facilitate interdisciplinary science collaborations between past and contemporary climate scientists, and foster close collaboration between early-stage and established scientists to build future European research capacity.

It is highly likely that this Action will produce a positive impact on the past climate research field within the European scientific community. Encouraging the use of similar protocols, standardized measurements and methods across the full range of environments and ecosystems within Europe will stimulate cooperation and facilitate a regional perspective on the rates, timing and magnitude of past climate change, providing invaluable insights into the likely impacts of future variability.

Current state of knowledge

At present, a complete integration of past climate and environmental reconstructions to constrain the predictive ability of climate models has not yet been achieved, although several past international initiatives have been developed with this aim. Most importantly, the North Atlantic INTIMATE project (Walker et al., 2001) was to synthesise ice-core, marine and terrestrial records that span the period at the end of the last glacial period (the ‘Last Termination’, 22,000 to 11,700 years ago; Walker et al., 2009). Their key objective was to determine whether abrupt climatic changes during that period, as reflected in a range of proxy records, were regionally synchronous or whether there were significant ‘leads’ and ‘lags’ between the atmospheric, marine, terrestrial and cryospheric realms (Lowe et al., 2008). A major difficulty concerns the wide usage of climatostratigraphic terms that were originally defined with specific reference to events in Scandinavia, such as ‘Younger Dryas’, ‘Bølling’ and ‘Allerød’ (Björck et al., 1998), which cannot have the same climatostratigraphic meaning around the globe, nor can they be used, sensu stricto, as chronostratigraphic units, because of the timetransgressive nature of climate change (Lowe et al., 2008). In order to standardise stratigraphical procedures and to clarify the sequence, timing and duration of events during the Last Termination, INTIMATE advocated an Event Stratigraphy approach, using the GRIP isotopic record as the regional stratotype, as this was considered to provide the best-resolved and most complete template for climatic events during the Last Termination in the North Atlantic region. Other records based on independently determined palaeoclimatic reconstructions and age models from the terrestrial and marine realms have since been compared to the ice-core stratotype, replacing the conventional (Nordic) chrono/climatostratigraphic terms as the standard for comparison (Walker et al., 1999).

Establishing the precise order of events during the Last Termination has proved a challenging goal, however, principally because of the different approaches to using proxy data and dating methods to generate quantified climate reconstructions and robust independently-derived geochronological frameworks spanning individual climatic episodes (Lowe et al., 2008). Undertaking a unified approach has become particularly critical in light of recent findings from the Greenland ice-core records that have demonstrated climate shifts can occur within a year (Steffensen et al., 2008). Fortunately, recent developments in quantified climate reconstruction (e.g. using chironomids, Coleoptera, isotopes and pollen), time-parallel marker horizons (e.g. vitreous volcanic ejecta (tephra) which have radically extended the range of tephrochronology across Europe into areas not previously considerable suitable for this approach e.g. Turney, 1998; Blockley et al., 2005; Turney et al., 2006) and developments in comprehensive Bayesian statistical analysis (Bronk Ramsey, 2001, 2007), now allows the comprehensive integration of different datasets and the rigorous comparison of records at a level of precision hitherto not considered possible.

It is now recognized that the scientific questions have evolved since the original inception of the group. A truly dynamical understanding can only be achieved with a companion modelling approach. The scientific community’s ability to forecast the rates and magnitudes of future change is limited by numerical models of climate change, which in turn are limited by the lack of high-quality data on how past climate has varied over time and the mechanisms that drove these changes. This proposed COST Action therefore aims to better understand the impact and mechanisms of rapid and extreme climate change, thereby reducing the uncertainty of future predictions.

Category: The Action

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