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Climate Change: Human versus Natural Causes

Is the earth warming this rapidly on its own?

May 7,2014 - Human causes on climate added to natural effects have raised temperatures significantly higher than would have occurred with natural effects alone. The May, 2014 National Climate Assessment indicates that around 1980 a clear pattern emerged that showed the planet was warming due to activities of people. These included burning fossil fuel and destroying natural systems that captured carbon.

The differential gradually widened, and by 2000 the models estimated that the earth's atmosphere was more than 1 degree Fahrenheit hotter than it would have been if society had no influence.

The models show a major human influence

Human effects added to natural effects have raised temperatures significantly higher than would have occurred with natural effects alone.
Source: National Climate Assessment, May, 2014. Figure 2.3

Citing the work of Markus Huber and Reto Knutti (Nature Geoscience, June 2011), the assessment produced an interactive graphic (from which the image above is adapted) to show that temperature on the planet would have been relatively stable over the last century if basic geophysical effects had been the only driving force of climate. These forces include volcanoes (which spew greenhouse gases into the air) sunspot cycles (which vary the intensity of solar energy reaching earth) and El Nino periods (which effect climate and weather over large portions of the earth because of thermal changes in the Pacific Ocean).

Global Warming Factors

"Oil used for transportation and coal used for electricity generation are the largest contributors to the rise in carbon dioxide that is the primary driver of observed changes in climate over recent decades," the assessment said.

However other socio-economic factors are important as well. The production of corn-fed cattle for beef alters the digestion of the cattle, causing them to emit methane as a waste product of their unnatural diet. Cows that eat grass from a pasture or prairie, as is their natural evolutionary dietary behavior, do not emit large amounts of methane as waste. Methane is an extremely potent greenhouse gas, trapping more heat than the same volume of carbon dioxide molecules.

Just as certain economic practices put carbon and greenhouse gases into the atmosphere, other practices prevent its removal or storage.

"Expansion of urban and suburban areas is responsible for much of the current and expected loss of U.S. forestland, although these human-dominated areas often have extensive tree cover and potential carbon storage," the report said.

Deforestation of large swaths of old growth forest deprive the environment of a major carbon sink. Trees absorb carbon dioxide as part of their natural cycle, break it down to carbon which is stored in their structure. A major portion of this carbon is eventually returned to the atmosphere when the tree dies and decomposes, but for several decades it has a beneficial home in the timber. Also, the release is gradual, rather than abrupt as int the case of burning fossil fuels.

Effect on oil and gas processing

In one ironic feedback loop, the fossil fuels that are causing much of the warming are as likely to fall victim to the effects of the climate change as other sectors of the economy. The assessment pointed out that much of the nation's refinery capacity is near coastal areas that will be altered by sea level rise and other effects.

As rising sea levels and increased storm surges pound the coasts, refineries and off-shore drilling operations would see their production curtailed in unexpected ways.

"As temperatures and sea levels increase, changes in marine and coastal systems are expected to affect the potential for energy resource development in coastal zones and the outer continental shelf," the assessment said.

"Oil and gas production infrastructure in bays and coves that are protected by barrier islands, for example, are likely to become increasingly vulnerable to storm surge as sea level rises and barrier islands deteriorate along the central Gulf Coast. The capacity for expanding and maintaining onshore and offshore support facilities and transportation networks is also apt to be affected," it continued.

Human activity, such as burning fossil fuels and cutting down forests, has added increasingly large amounts of carbon to the atmosphere.
From the National Climate Assessment, 2014