Recent increases in "greenhouse gases" (or GHGs) leading to global climate change are a growing concern worldwide, with potentially dramatic implications for local communities, economies, and environments.  Quality of life may be greatly impacted in ways as yet unknown or only estimated.

GHGs are found in trace amounts in Earth's atmosphere, which is composed of approximately 78% nitrogen and 21% oxygen; the remaining 1% contains all the greenhouse gases such as carbon dioxide, sulfur dioxide, nitrous oxides, and methane, among others.  These gases are transparent to light, so the sun's rays easily come through the atmosphere to reach Earth's surface.  However, these same gases trap heat by preventing short-wave radiation from exiting the atmosphere back into space.  Were it not for the presence of GHGs, the planet would be a much colder place, very likely inhospitable to humans and other species presently extant. 

Earth has experienced wide variations in greenhouse gas levels throughout its five-billion-year history.  Volcanoes, decomposition of organic matter, and the respiration of animals all produce GHGs.   Research on ice cores (which retain atmospheric "memory" in much the same way as trees' rings) shows that increases in greenhouse gases are correlated predictably with increased surface sea and land temperatures. 

Since humans came on the scene, atmospheric chemistry remained fairly stable when compared to other geologic eras.  However, while humans have indeed lived through ice ages and warming trends, the rapid rise of greenhouse gases since the beginning of the Industrial Revolution about 150 years ago lends a potential of greater extremes in temperature than seen before in the span of human existence.  An important issue now, therefore, has to do with "anthropogenic," (or "man-made") sources of GHGs, which are emitted primarily during the burning of fossil fuels, and from forest clearing and burning, from livestock (flatulence and manure), and from organic decomposition (anthropogenic in landfills).

A common misperception with respect to climate change was engendered inadvertently by the term "global warming," which was first widely used beginning in the 1980's, and which implied a uniform and consistent warming of land and sea worldwide.  A more accurate prediction of change associated with warming trends (which are clearly evident in the data) is the expectation of an increase in statistically anomalous (or rare) weather events.  Such predictions have been borne out in recent data, which show dramatic increases in the frequency and intensity of global storm events.  Floods, tornadoes, and droughts (the latter sometimes accompanied by fires) are on the increase, and are occurring in unexpected geographic locations. 

To use hurricanes (and cyclones) as an example, each degree increase in surface water temperature above about 82 degrees is akin to pouring gasoline on a fire, in terms of increasing the intensity and storm-force wind diameter of a tropical storm.  Hurricane Katrina grew to Category 5 status in the Gulf of Mexico in late August 2005, at the point where the surface water temperature was 90 degrees.  A few weeks later, in an even warmer Gulf, Hurricane Rita was measured as having the lowest central minimum pressure on record (central minimum pressure is a reliable indicator of hurricane severity, with lower meaning more severe), and also the largest storm-force wind diameter on record (the hurricane was over 400 miles wide).  While any one storm cannot be used as "proof" of climate change, its size and intensity are nevertheless inextricably related to simple properties of physics.

While the implications of changes in atmospheric physics are indeed global in scope, practical solutions for anthropogenic greenhouse gas emissions must be initiated and carried out at local levels.   

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