Friday, May 6, 2011

Human influence on climate change

Anthropogenic factors are human activities that change the environment and influence climate. In some cases the chain of causality is direct and defines, while in others it is less clear. The biggest factor of present concern is the increase in co2 levels due to emissions from fossil fuel consumption, followed by aerosols, which exert a cooling effect, and cement manufacture. Other factors, including land use, ozone depletion, animal agriculture and deforestation, also affect climate.
1)      Fossil fuels:  Begging with the industrial revolution in the 1880s and accelerating ever since, the human consumption of fossil fuels has elevated co2 levels from a concentration of ~280 ppm to ~ 387 ppm today. 
2)      Aerosols:  Anthropogenic aerosols, particularly sulphate aerosols from fossil fuel combustion, exert a cooling influence. This together with natural consistency. 
3)      Cement manufacture: Cement manufacture contributes co2 when calcium carbonate is heated, producing lime and carbon dioxide, and also a result of burning fossil fuels.
4)      Land use: Prior to widespread fossil fuel use, hu8manities largest effect on local climate is likely to have resulted from land use. Irrigation, deforestation and agriculture fundamentally change the environment. For example, they change the amount of water going into and out of a given location. They also may change the local albedo by influencing the ground cover and altering the amount of sunlight that is absorbed. For example, there is evidence to suggest that the climate of Greece and other Mediterranean countries was permanently changed by the widespread deforestation between 700 BC and 1 AD, with the result that the modern climate in the region is significantly hotter and drier, and the species of trees that were used for shipbuilding in the ancient world can no longer be found in the sea. An assessment of conterminous U.S biomass burning speculated that the approximate 8 fold reduction in Wild land Fire Emissions from the preindustrial era to present caused by land use changes and land management decisions may have had a regional warming affect if not for fossil fuel burning emissions increase occurring concurrently. 
5)      Livestock: This however includes land usage change, meaning deforestation in order to grazing land, as well as livestock natural gas emissions.


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