The aims of this group are (i) to reconstruct past climates and ecosystem responses on timescales from tectonic (106-year) to historical (102-year); (ii) to decipher the climatic signature of critical intervals in human evolution; and (iii) to contribute towards an evolving theoretical framework of long-term climate change. We have developed and applied novel methods for climate reconstruction from sediments from marine, lacustrine and terrestrial settings using palaeoecological, geochemical and isotopic methods supported by advanced numerical techniques and applied sophisticated modelling approaches to pressing palaeoclimatic problems and led initiatives for data-model comparison.
Recent research highlights:
- Climate variability on tectonic timescales (Brierley, Maslin). Work on East African lake sediments has led to the development of new hypotheses for Plio-Pleistocene climate and human evolution in East Africa. New climate modelling results for the Early Pliocene have drawn attention to the role of reduced meridional sea-surface temperature gradients on the permanent El Niño-like state and to the critical importance of feedbacks between tropical cyclones and the tropical ocean.
- Climate variability on orbital and suborbital timescales (Holmes, Mackay, Maslin, Tzedakis) Analysis of long continental and marine archives from S. Europe and the Portuguese margin has provided new insights into (i) the coupling between low- and mid-latitude hydrological changes and (ii) the influence of background climate state on the nature of millennial-scale variability. Analyses of long continental records of central Asian climate from Lake Baikal have identified teleconnections to N. Atlantic ice-rafting events. Incorporation of water-isotope tracers into climate models and data-model comparisons of rapid climate change events have provided a comprehensive synthesis of the 8200-year event across the Atlantic. High-resolution analyses of Holocene lake-sediment sequences have provided evidence for the nature and causes of monsoon variability in West Africa, Western China and Central Asia and have led to new hypotheses for the rapidity of aridification of North Africa during the mid Holocene. Examination of past interglacials has provided new insights into factors controlling interglacial duration and on the natural length of the current interglacial in the absence of anthropogenic interference.
- Climate variability over the past 2000 years (Holmes, Jones, Mackay, Flower) Research in the Russian Arctic has demonstrated a dramatic response of lake ecosystems to anthropogenic warming against a background of longer-term natural changes. In North Africa, changes in effective moisture reconstructed from rapidly-accumulating lake sediments have revealed a complex interplay between climate change and anthropogenic effects in lake-basin hydrology. Lake-sediment sequences from Northeastern and west-central China have revealed major changes in precipitation regime in the summer monsoon region, and show that the Little Ice Age was not only a period of aridity, but was marked by dramatic changes in atmospheric circulation. Multiple-archive (lake-speleothem, lake-speleothem-ice core) Holocene reconstructions in Europe and Central Asia have been used to deconvolve complex carbonate oxygen-isotope signals in lakes and demonstrated a strong atmospheric circulation control on terrestrial oxygen-isotope records.