The Climate Dimension
Prof. Karin Holmgren, Martin Finné, Dept. of Physical Geography and Quaternary Geology, Stockholm University.
The overall aim of the project “The Urban Mind” is to understand the cultural and environmental factors behind urban development. The project is organised in six research frames and every frame focuses on a specific temporal and spatial extent. The specific aims of the sub-project “the climate dimension” are, according to our understanding, to
■compile and synthesize data available on climate, hydrology and environmental change from sites selected to suit the research frames 1-6.
and to, in cooperation with scientists responsible for the specific research frames,
■integrate data on the climate dynamics with data on cultural dynamics aiming at an increased understanding of historical societal strategies that seem most effective for survival and development in a changing environment.
■up-scale case studies to regional scales and modern times
■provide data useful for the identification of strategies suitable for a sustainable future.
Benefit of achieved aim
One motive behind engaging in research on the complexities and dynamics of societal and environmental processes, over time and space, is explicitly to scrutinise simplistic hypotheses based on climate–society interactions (McIntosh et al., 2000, Costanza et al., 2007). A time perspective, reaching beyond the information available from instrumental records is needed for a better understanding of regional global climate dynamics and issues surrounding environmental change. Research on past interactions between climate and societies is expected to provide lessons of importance for present and future situations. Our findings are expected to increase the understanding of the complex interactions between climate/environment and societies that may lead to different developments in time and space. Within the Urban Minds project, research carried out on both the evolution of natural climate variability and the interrelation between climate, society and development in a long time perspective is expected to contribute new information of importance for advancing our capacity to predict and adapt to future trends and to create a sustainable human society.
The sub-project “the climate dimension” crosses over all temporal and spatial scales of the project and all research frames.
The on-going global warming is one of many serious challenges that the global society is facing today. Regional scenarios predict severe drying in the Mediterranean and Middle East regions over the coming 100 years (IPCC 2007). The warnings about large problems due to the recent and predicted future global warming need attention and all tools available for preparation and adaption to a changing future should be utilised. One such tool is history. One may argue that this is the first time in history that we face a situation like the present one, and therefore we can not learn from history. But, if we consider regional and local scales both abrupt and large climate changes have occurred in the past, although the causes were different from today and the changes may not have been of the same global character. It should however be recognised that local scale processes are of key importance for communities and thus society.
Available paleoclimate records
High resolution climate records covering the past circa 10000 years are available at several locations from the focal regions Mediterranean and Middle East (Fig. 1), as well as from the regions that will be treated as “control studies” for the project. These records are based on analysis of dated lake sediment, peat sections, ice cores, trees and speleothems (Battarbee et al., 2004 and references therein). The records are interpreted to reflect changes in temperature, vegetation, moisture variability and/or lake level fluctuations.
The general pattern of Holocene climate variability, as well as regional to local trends, is recorded in the eastern Mediterranean region. Extended climate and environmental information is available from marine, lacustrine and terrestrial sediments in the region, for example from assemblages of pollen, diatoms, ostracodes and planktonic foraminifera. A number of records come from stable isotope analyses of carbonates from speleothems (stalagmites and stalactites), corals, deep sea and lacustrine cores and mollusc shells. Other methods that have been used include lake level reconstructions, studies of geomorphology and of fluvial and aeolian sediments. Also dendrochronology has shown promising results.
The most widespread method employed is the study of past vegetation dynamics through palynology (pollen studies). Sequences covering the Holocene, and beyond, are available for most of the region (e.g. Rossignol-Strick, 1999). A problem with this approach is the fact that humans have been an important element for a long time, affecting and altering the natural vegetation both by degrading (e.g. deforestation) and promotion/proliferation (e.g. cereal and olive cultivation) and thereby hampering climatic interpretations from pollen records (Roberts et al., 2004; Stevens et al., 2006; Eastwood et al., 2007; Kaniewski et al., 2007).
Dendroclimatology gives an opportunity to get highly resolved (annual to subdecadal) climate data, mainly on precipitation in this region (Griggs et al., 2007). A drawback with the method is that it is hard to retrieve wood of old ages and thus to extend the records far back in time. Hence most dendrochronology records cover the last 1000 years or less. Another problem with dendroclimatology is that long climate trends are less well represented because of the statistical treatment needed to perform to adjust for changes in growt rate due to the trees age.
Stable isotopes from speleothems, foraminifera and other terrestrial, lacustrine or marine carbonates can provide information on past changes in temperature, rainfall and vegetation cover. Speleothems often serve as a remarkable archive of data, describing local and global climatic and environmental conditions for the period of time in which they grew (McDermott, 2004; Fairchild et al., 2006). They are well suited for U-series dating; yielding ages directly in calendar years and the mechanisms controlling speleothem growth are sensitive to external, often climatically driven processes.
The problem of correctly determine the age of material from natural archives used for paleoclimate studies is ubiquitous. Radiocarbon dating presents the most effective means of dating material containing organic carbon whilst other methods are employed when dating for instance speleothems. Raw radiocarbon dates need to be calibrated, to compensate for changing levels of 14C in the atmosphere, before they can be used as calendar dates. In this work calibrated radiocarbon dates will be converted to BCE/CE dates with the 1950 CE level of 14C in the atmosphere considered as the nominal level. Raw radiocarbon dates were calibrated before converted into BCE/CE dates.
Methods and data
As a first preliminary work plan we propose to do the following:
1. Literature review and data base development (August 2008 - April 2009). An extensive mapping of existing research findings on high resolution climate evolution, will be performed. We will initially focus on Frame 4. Data on climate and hydrology (e.g. temperature, humidity, precipitation, evapotranspiration, runoff), and possibly on environmental (e.g. soils, vegetation, topography) change will be compiled and analysed. The result will be organised as descriptions and reconstructions over time and space. Strengths and weaknesses of previous research will be identified. The review will provide an enhanced theoretical and empirical foundation and also identify key questions for future detailed studies.
2. Integrated analysis and compilation (Dec 2008 – Dec 2009). As soon as climate data has been independently compiled, the results will be compared to the results from the studies of the societal development. We will look for cases where well documented climatic changes appear to have had no detectable cultural impact as well as those where links between climatic and cultural changes have been inferred. Specific attention will be paid to distinguishing between natural indicators of climate and environmental change and cultural indicators. Theoretical considerations will be performed regarding the integration of data of different character (social, environmental, climatic..), and different spatial and temporal scales and to the development of organising the data to make them suitable for system modelling. Theoretical and experimental considerations of methods for temporal and spatial upscaling of data will form a major task.
3. Workshop (Preferably March 2009). The purpose of this 2-3-day workshop will be two fold: First to present and discuss the results of the literature review and analysis and second to discuss forcing and feed backs in the coupled human and natural systems. Apart from the Urban Mind project scientists, leading scientists within the fields of climate of the focal regions will be invited, as well as scientists working with coupled systems and dynamic modelling.
4. Paper and book chapter writing (May 2009-Dec 2009). Initial writing will start earlier but during this time frame Holmgren will concentrate her work on writing.
Our contribution to meetings during autumn 2008:
September, 6, Uppsala. Introductory lecture by Karin Holmgren on climate methodology and climate development during the Holocene in the Urban Mind regions. First project research results presented and discussed by Martin Finné.
October 22, Department of Physical Geography and Quaternary Geology, Stockholm University (host). Presentation and discussion of the first compilations of climate data. Discussions on cooperation between the climate dimension and the different frames.