The apparent cause of global warming is something called the greenhouse effect, a process in which gases in the Earth's atmosphere, especially water vapor and carbon dioxide, absorb energy from the Sun, resulting in increased heat in the Earth's atmosphere, oceans, and land. Some of this warming is actually natural, the outcome of longwave, or infrared, radiation from the Sun being reemitted from the Earth's surface back into the cooler atmosphere above by way of trace gases. Scientific research has shown that the temperature of the Earth has been increasing by small increments for at least 200 years. However, the burning of fossil fuels for energy emits carbon dioxide and other so-called greenhouse gases (methane, water vapor, ozone, nitrous oxide) into the Earth's atmosphere. And research has shown that as the concentration of these gases in the Earth's atmosphere has increased through human energy consumption, the balance of outgoing, infrared radiation and incoming radiation has been disrupted, trapping more radiation in the atmosphere. This, say many scientists, has caused the Earth to become warmer than it might have been without the use of fossil fuels for energy. Just how much warming is the direct result of human activities or how much will occur in the future, however, is disputed by the scientific community. Most scientists, however, do agree that human energy consumption has had an impact on the overall increase in the Earth's temperature, and many (but not all) scientists agree that most of the warming over at least the past 50 years is probably due to an increased concentration of greenhouse gases.
Recently Robert Correll, a senior fellow of the American Meteorological Society and a U.S. authority on global climate change, led the International Arctic Science Committee, a scientific team commissioned by the United States and seven other countries, in a study of the impact of climate change on Greenland, above the Arctic Circle. This is a region where glacial ice has been melting at a rate that some scientists find alarming. Correll estimated that about 100-million-plus acres of the region's ice has melted over 15 years. Reportedly, 98 percent of the world's mountain glaciers are also melting, so quickly that, according to Corell, in 100 years the runoff water will push sea levels around the world three feet higher.43
In 2004 Correll's team produced a report, the Arctic Climate Impact Assessment. The report found that harmful effects on the food chain, ocean currents, storm systems, and indigenous life have resulted from the rapidly melting glacial ice. Correll also reported that the polar bear population in Greenland has dropped by more than 200 bears since the mid-1990s as a result of the loss of habitable ice. The melting ice is attributed to an increase in global temperature, which, in turn, has been traced back to greenhouse gas emissions from fossil fuels. In February 2007 a report by the United Nations' Intergovernmental Panel on Global Climate Change (IPCC), authored by 600 international scientists, unequivocally concluded that the Earth's temperatures were increasing. It also stated that the rise in global temperatures was almost certainly caused by increased carbon dioxide and other greenhouse gases in the atmosphere and that the increase in these gases was more than 90 percent likely the result of human activities. The United States endorsed the IPCC report.44 Additionally, the U.S. Supreme Court ruled in April 2007 that greenhouse gases are polluting and ordered federal environmental officials to consider limiting emissions of these gases from cars and trucks.
According to EIA statistics the United States emits more greenhouse gases than any other nation. Of all the greenhouse gases, carbon dioxide is considered to have the greatest potential for causing pollution and global warming, and fossil fuels, by far, contribute the greatest share of carbon dioxide emissions to the Earth. The United States is the largest contributor of carbon dioxide emissions per capita among countries in the Organisation for Economic Cooperation and Development (OECD), an international organization of countries with market economies and pluralist democracies. The high index of U.S. carbon dioxide emissions when compared with that of other OECD countries is attributed to the United States' strong demand for energy, particularly energy from a carbon-intensive mix of sources. According to EIA data, the United States consumed a total of 91.09 quadrillion Btu of energy during the first 11 months of 2006, and 85 percent of this total, or 77.85 quadrillion Btu, was from fossil fuels. In the United States, of all the energy derived from fossil fuels, nearly half, or 36.87 quadrillion Btu, was from petroleum alone during these first 11 months, and EIA projections forecast that petroleum consumption will increase almost 75 percent by the year 2030.45
Between 1990 and 2005 emissions from greenhouse gases increased by 17 percent in the United States, according to Emissions of Greenhouse Gases in the United States 2005, a report released by the EIA. Petroleum accounted for 2,614 million metric tons of carbon dioxide emissions in 2005 in the United States, while natural gas and coal accounted for 1,178 and 2,142 million metric tons, respectively. Total carbon dioxide emissions reached just beyond 6 billion metric tons in 2005.46
Carbon dioxide is the primary product of burning oil and coal for fuel. Natural gas burns much more cleanly but still produces carbon dioxide emissions. Because it is mostly methane gas, natural gas can also leak traces of methane into the environment. Of the carbon dioxide emissions attributable to petroleum, motor gasoline accounted for the greatest share, 1,170 million metric tons. Carbon dioxide emissions from fossil fuel use in the United
States are also projected to be 54 percent higher in 2020 than in 1990, despite a reduction in the share of coal in total power generation.
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