This thesis is a global study of the changes in the plant emissions of the dominant Biogenic Volatile Organic Compounds (BVOC) in the last millennium resulting from changing environmental conditions, largely induced by humans. BVOC emitted by vegetation have multiple impacts on atmospheric chemistry and physics, for instance changes in BVOC emissions significantly change the concentrations of aerosol in continental regions, affect ozone formation and change the oxidizing capacity of the troposphere. These processes are relevant from a climate change and air quality perspectives. The variability of global fluxes of isoprene, monoterpenes and sesquiterpenes (terpenoid BVOC) over the last millennium is evaluated using the Model of Emissions of Gases and Aerosols from Nature (MEGAN). The model is driven with meteorology input data from an Earth System Model, CO2 atmospheric concentrations estimated from ice samples and model reconstructions of the global changes of vegetation.
The results show that global isoprene emissions have decreased 7.3%, monoterpene emissions have increased 9.8% and sesquiterpene emissions have increased 15.1% during the period 1950-1990 as compared to 1000-1800. The results suggest that the variation of isoprene emissions is governed by land-use changes, while monoterpenes and sesquiterpenes variations are dominated by temperature. Regional changes on the isoprene, monoterpene and sesquiterpene emission distribution are larger than global changes in many locations and could have had a significant impact on the chemistry and aerosol dynamic processes in the atmosphere in the last millennium. This thesis lays a basis for a future quantification of the effect on atmospheric chemistry cycles and the organic aerosol yield from biogenic organic precursors.
