Mar 11, 2013

Global Warming and Climate Change

The temperature of the Earth has fluctuated throughout the planet's history, causing both ice ages and periods of intense heat. However, beginning with the Industrial Revolution in the late 18th century, human activities began to change the composition of the atmosphere and the Earth's climate. While some people disagree that humans are having a significant effect on global climate, the Intergovernmental Panel on Climate Change (LPC.C.), a group of several thousand scientists commissioned by the United Nations, reported in 2007 that "the evidence of global warming is now unequivocal" and said that human activity is the major contributor. The terms climate change and global warning are often used interchangeably, although global warming is only one factor in the larger issue of climate change.

The essential differences between historical climatic change and human-caused global warming include both the rate of the change, which is faster than that to which many plant and animal species can adapt, and also the sizable human population of the Earth, which could cause serious shortages of land, water, and food in the event of a major climate shift. Most climatologists agree that the Earth warmed by 1.1 degrees Fahrenheit between 1850 and 1990, an alarming rate considering that worldwide temperatures rose only 9 degrees Fahrenheit since the end of the last ice age, 12,000 years ago. In fact, the eight warmest years recorded since 1850 occurred between 1998 and 2009. At its current rate, the Earth is likely to warm by an additional 3 to 7 degrees Fahrenheit by the year 2100. According to the LRC.C., such warming would cause both drought and rising sea levels, and destroy water supplies, forests, and agriculture in many parts of the world.

Global warming occurs when certain atmospheric gases prevent the Earth’s from reflecting excess sunlight, instead trapping heat in the Earth's atmosphere, oceans, and land. Some of these "greenhouse gases" occur naturally and are necessary to keep the Earth's surface warm enough for human life, but the higher concentrations produced over the last two centuries are trapping more heat than the Earth can release.

Carbon dioxide, or CO2, is the most prevalent greenhouse gas. Its presence in the atmosphere has increased by 36 percent since before the Industrial Revolution, when people began to burn fossil fuels including oil, coal, and natural gas, and burn trees for deforestation. Methane, the second-biggest contributor to global warming, is now at 148 percent of preindustrial levels and is emitted primarily by decomposing landfill waste, large-scale cattle raising, natural gas leaks, rice paddies, and coal mining.

Many climatologists predict that global warming will also change weather patterns. There is evidence that heat waves, storms, and droughts have already increased in frequency and intensity, and the U.S. National Climatic Data Center reports that extreme extra-tropical cyclones over the North Atlantic have increased since 1988. However, temperature increases and weather changes are not uniform, and some places will, theoretically, experience more severe effects than others. Increasing temperatures expand the volume of ocean water and melt glacial ice, and, as a result, climatologists expect the sea level to rise between 3.4 inches and 3 feet above 1990 levels by the end of the 21st century. In the US., a 3-foot rise would flood 7,000 square miles of dry land --mostly in the Southeast -- and would destroy a comparable area of coastal wetlands, erode recreational beaches, exacerbate coastal flooding, and increase the salinity of aquifers and estuaries. Industrialized continental nations like the United States could probably sustain the population shifts caused by such changes, but globally, about 1.75 billion people live within 40 miles of the sea, mostly along low-lying islands, flood plains, and estuaries.

There are two principal ways of responding to climate change: mitigation and adaptation. Mitigation involves measures that will reduce human contributions to climate change. An example of this approach is the "cap-and-trade" system designed to reduce CO2 emissions by giving companies that produce large quantities of C02 financial incentive to reduce their emissions.

Whereas mitigation deals with the causes of climate change, adaptation addresses its effects. To deal with changing levels of precipitation, for example, water supply systems can be linked and expanded. However, adaptations can have adverse environmental consequences themselves; extra air conditioning requires more electricity, for example, and seawalls can prevent natural wetland formation. Furthermore, poor nations have few adaptive options because they do not have the necessary social, political, or financial resources to implement them. Bangladesh, for example, cannot afford flood protection for its low-lying coastal areas, and subsistence farmers in Africa may not be able to survive even a brief drought.

One of the first international efforts to manage global warming was the 1997 conference in Kyoto, Japan, where representatives of more than 150 countries reached a tentative agreement to reduce greenhouse gases by an average of 5 percent worldwide (from 1990 levels) by 2010. By 2009, 187 countries had ratified the Kyoto Protocol, though the agreement expires in 2012. World leaders met in Copenhagen in December 2009 in an effort to reach a new agreement, which called on developed nations to start work immediately; the U.S. agreed to reduce emissions by 14-17 percent below 2005 levels by 2020.

Emissions reduction strategies include: reducing electricity use through energy-efficient factories and appliances; replacing coal-fired power plants with solar, hydroelectric, or wind power; raising fuel efficiency standards for automobiles and reducing automobile use; insulating buildings to reduce heating and cooling needs; and regulating major fossil fuel suppliers and greenhouse gas producers. Although scientists cannot definitively predict what amount -- if any -- of greenhouse gas reductions would curtail global warming, most agree that a large-scale international effort could reduce the severity of the consequences. (The New York Times ‘Smarter by Sunday – 52 Weekends of Essential Knowledge for the Curious Mind’)