Human Influences of Climate Change

Human Influences of Climate Change

Human Influences on Climate Change

Anthropogenic factors are acts by humans that change the environment and influence climate. Various theories of human-induced climate change have been debated for many years. In the late 1800s, the Rain follows the plow theory had many adherents in the western United States. The biggest factor of present concern is the increase in CO2 levels due to emissions from fossil fuel combustion, followed by aerosols (particulate matter in the atmosphere) which exerts a cooling effect and cement manufacture. Other factors, including land use, ozone depletion, animal agriculture and deforestation also affect climate.

Fossil Fuels

Beginning with the industrial revolution in the 1850s and accelerating ever since, the human consumption of fossil fuels has elevated CO2 levels from a concentration of ~280 ppm to more than 380 ppm today. These increases are projected to reach more than 560 ppm before the end of the 21st century. It is known that carbon dioxide levels are substantially higher now than at any time in the last 800,000 years. Along with rising methane levels, these changes are anticipated to cause an increase of 1.4–5.6 °C between 1990 and 2100 (see global warming).

Aerosols

Anthropogenic aerosols, particularly sulphate aerosols from fossil fuel combustion, are believed to exert a cooling influence. This, together with natural variability, is believed to account for the relative "plateau" in the graph of 20th century temperatures in the middle of the century.

Cement Manufacture

Cement manufacturing is the third largest cause of man-made carbon dioxide emissions. While fossil fuel combustion and deforestation each produce significantly more carbon dioxide (CO2), cement-making is responsible for approximately 2.5% of total worldwide emissions from industrial sources (energy plus manufacturing sectors).

Land Use

Before fossil fuel became such a global issue, land use by humans had the biggest impact on local climate. Land use such as irrigation, deforestation, and agriculture fundamentally changed 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 (the amount of sunlight reflected off the earth) 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 widespread deforestation between 700 BC and 1 AD (the wood being used for shipbuilding, construction and fuel), 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 area. "

William Ruddiman developed a hypothesis that caused a lot of argument. Called the early anthropocene (1) hypothesis, Ruddiman theorized that the increases in carbon dioxide and methane may have caused the rise of agriculture along with deforestation. He went on to say that he thought that the responsibility for the delay of the next glacial period were due to the increases of CO2 and methane.

In 2007 a Jet Propulsion Laboratory study determined that California's average temperature has risen about 2 degrees over the past 50 years, with a much higher increase in urban areas. The change was attributed mostly to extensive human development of the landscape.

Livestock

Responsibility for 18% of the world’s greenhouse gas emissions is due to livestock--including the deforestation of pasture land. (2006 United Nations report, "Livestock's Long Shadow.")

One of the best examples of huge deforestation is found in the Amazon Rain Forest where the development of forced livestock resulted in 70% loss of forest. (2006 UN FAO report).

"In addition to CO2 emissions, livestock produces 65% of human-induced nitrous oxide (which has 296 times the global warming potential of CO2) and 37% of human-induced methane (which has 23 times the global warming potential of CO2)." (2)


(1) http://dictionary.reference.com/browse/anthropocene
(2) http://en.wikipedia.org/wiki/Climate_change#Human_influences_on_climate_change