This paper describes a global-scale modelling approach for investigating the structure and productivity of terrestrial vegetation in the Mesozoic era. General circulation model (GCM) palaeoclimate simulations (by the University of Reading) for Kimmeridgian and Cenomanian time are described as driving datasets for the University of Sheffield Dynamic Global Vegetation Model (SDGVM). The validity of these GCM palaeoclimates is reviewed. Global patterns of terrestrial net primary productivity (NPP) and leaf area index (LAI) have been simulated with the SDGVM, which models plant physiological processes and the biogeochemical cycling of carbon and nitrogen in soils and vegetation. An important feature of this modelling approach is that it requires no underlying map of soils or vegetation type. Global NPP in Kimmeridgian and Cenomanian time was high (117.6 and 106.8 Gt Ca1, respectively) compared with the present-day level (57.0 Gt Ca−1). The high concentrations of atmospheric CO2 at each interval significantly influenced the NPP and LAI of Mesozoic vegetation, to an extent dependent on climate. CO2 effects on the structure of vegetation in Kimmeridgian and Cenomanian time were sufficient to markedly influence key land surface variables required by GCMs for climate predictions, and point to the need to include direct CO2–vegetation interactions in climate models. Two approaches to testing the modelled NPP patterns were devised, one using palaeobotanical information on tree growth, and the other based on a comparison of measurements and predictions of the stable carbon isotope ratios of fossil plants. Both approaches provided some support for the global-scale simulations, indicating the feasibility of modelling vegetation activity in ancient climates from a knowledge of present-day processes.
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The climate of the early Earth was probably very warm and has, in general, reduced since the Archean. However, it now seems that the world is about 0.6°C warmer than it was 100 years ago and estimates of the rate of global warming over the next century range from 0.16°C to 0.35°C per decade. Concurrently, global sea-level is predicted to rise from 2.4 to 10 cm per decade. These rates of change are much faster than those normally associated with the geological record, causing geologists and palaeontologists to reassess their data and their forecasts on rates of future change.
With the current interest in global climatic change and, more specifically, with global warming, it is clear that palaeontologists have valuable information to provide on the impacts of past climatic change. This volume contains papers from an international array of such geologists and palaeontologists, showing how studies of micro- and macrofossils, plant and vertebrate fossils from a range of geological ages have contributed to our understanding of how climate affects both local and more widespread areas. The contributions are arranged in geological order, ranging from the Permo-Carboniferous to the post-glacial recovery of the last 18,000 years, with an emphasis on climate change during the last two million years, particularly in NW Europe.
Climates: Past and Present will be of interest to palaeontologists, geologists and palaeoclimatologists who specialize in climatic reconstructions and any professionals enagaged in research into the geological aspects of climate change.