|
|
|
|
AcclimationPotential effects of some aspects of climate change on plant and soil processes. sources:
The Earth’s climate is dependent upon the radiative balance of the atmosphere. This balance is dynamic and subject to change due to both naturally occurring processes and anthropogenic influences that arise from human activities. Naturally occurring processes, such as the reduction in solar constant experienced when the solar system passes through clouds of galactic dust may induce climatic change in the longer term (>1000’s of years) but are of less direct significance to short term planning for climate change. However anthropogenic influences such as greenhouse gas emissions are predicted to have a rapid and near immediate affect on the Earth’s climate. The radiative balance of the Earth’s atmosphere depends upon the input of solar radiation and the relative abundance’s of atmospheric radiatively active gases, (e.g. greenhouse gases, clouds and aerosols {Watson, 1992 #1912}. Atmospheric carbon dioxide (CO2) is an important greenhouse gas and is now present in the atmosphere at 25% greater concentrations than the pre-industrial (1750-1800) value of 280ppm and is higher than at any time in at least the last 160,000 years. Further the atmospheric CO2 concentration is expected to rise from its current average level of 354ppm to 530ppm by the year 2050 and to 700ppm by the year 2100 {Watson, 1992 #1912}. The time taken for atmospheric CO2 concentration to adjust to changes in sources and sinks is of the order of 50-200 years. Consequently CO2 emitted into the atmosphere today will influence the atmospheric concentrations of CO2 for at least several centuries {Folland, 1990 #1910}. Changes to the atmospheric CO2 concentration and concurrent changes in the concentration of other infra-red absorbing gases in the atmosphere are expected to produce a greenhouse warming of the global surface in the order 0.3° C per decade or alternatively 3-4oC by 2100 {Watson, 1992 #1912}. Changes in both atmospheric CO2 concentration and global surface temperature are likely to have a profound affect on many physical, chemical and biological processes. Prediction of how vegetation growth and related soil processes will respond to these changes is critical to understanding the impacts of atmospheric change on both natural and crop ecosystems. Accurate prediction of changes in agricultural yields is vital to assessing the potential economic impacts of climate change. Further, prediction of the feedback dynamics of natural ecosystems on climate change is necessary to understand whether these systems will act as positive (enhancing) or negative (reducing) factors in a CO2 enriched atmosphere. The role of modelling and computer simulation Models and other analogies have always played an important role in the thinking of scientists and may consist of words, diagrams, mathematical notation or physical structures in representing the real system. Because no model can totally represent the real system in every detail the formation of a model always entails a degree of simplification or abstraction. In many cases the simplification applied is based upon a theoretical understanding of the system under study and a limited amount of direct experimental evidence. Experimental manipulation of the climate and atmosphere of enclosures around plants provides some direct evidence of the potential effects of climate change {Wyse, 1980 #1940; Wulff, 1983 #1941; Woo, 1983 #1942; Drake, 1989 #1116; Clough, 1981 #1945; Drake, 1994 #1921}. However, given the global scale of the changes in atmosphere and climate, and the diversity of natural and crop ecosystems, experiments can only provide a tiny fragment of the information needed. Further, they can only be conducted at the scale of a few square meters whereas understanding at the scale of square kilometres is needed. Predictive computer based models provide the only reasonable alternative to direct experimentation. The powerful personal computers that have become common in most laboratories during the last decade, as tools for planning experiments, collecting data, searching literature and analyzing results, are also ideal tools for formulating and running computer based models and simulations. |
Send mail to humph@essex.ac.uk with questions or comments about this web site.
|
