Global Warming

Variations in the energy output of the sun, changes in the relative positions of the sun and Earth, shifting locations of the continents, volcanic eruptions, and other alterations of atmospheric composition all combine to cause climate change. The long term changes in Earth's temperatures are encompassed within a range of natural variability. However, global warming refers to the relatively rapid, recent changes that are outside this range of natural variability. The mean global temperature of Earth has not deviated more than 1 degree Celsius from the average since the beginning of civilization. By 2100, Earth's temperature is forecast to increase from 1.5 to 4 degrees Celsius if present rates of warming continue. This rate of temperature increase is unequivocal in that it has no equal in the past half million years. The evidence for global warming is overwhelming, and includes melting glaciers and sea ice, rising sea level, increased heights of storm surges, a greater frequency of severe weather events (including category 4 and 5 hurricanes), an increased number and severity of floods, droughts, and wild fires, and an increase in the acidity of the world's oceans.

The burning of fossil fuels and deforestation during the last 100 years has increased the level of carbon dioxide (CO2) from 280 parts per million (ppm) to 390 ppm, and CO2 is a potent greenhouse gas. Countries around the globe have convened to find a resolution to this pressing problem as they met in Kyoto, Japan, in 1997, Copenhagen, Denmark, in 2009, and in Cancun, Mexico, in 2010. The Intergovernmental Panel on Climate Change (IPCC) is a body of more than 2,000 of the world's foremost atmospheric scientists, and is held to be a reliable source of information on all aspects of global warming. In their fourth assessment report published in 2007, these experts outlined the importance of the choices made by societies in determining the degree to which the planet will continue to warm in their “Special Report on Emission Scenarios” (SRES). The atmosphere will continue to warm throughout the next century. However, the boldness and efficiency with which individuals and governments act will make a substantial difference in the depth of the disasters that will ensue.