Global warming has stirred up much controversy in the past 20 years.  What the effects of increased global temperature may be, no one is certain.  Here are some of the more reliable speculations.  However, the science behind the warming trend that has accompanied our highly technological society is sound, and the trend is real.

Here are some articles that address the uncertainty in Global Warming assessment:
Article 1: "Most climate scientists are convinced they are right to warn us the prospect ahead is alarming unless we act soon. They accept there are uncertainties but say human activities are having a clear effect on natural climate change, and that the Earth could warm dangerously. Their critics say the evidence so far is not conclusive, and think the human impact is so small as to be negligible. But recent findings suggest there are real causes for concern at the speed with which the Earth is now heating up.
Article 2: Climate Legacy of 'Hockey Stick'
Article 3: BBC Climate Change Website

    Since the industrial revolution, heavy machinery and industrial processes have been developed that utilize energy derived from fossil fuels.  The process by which energy is extracted is almost entirely combustion.  Combustion of fossil fuels uses the energy given off by the breaking of Carbon-Hydrogen bonds for things like electricity and heat.  The biggest byproduct of this combustion is carbon, and this same carbon is part of our biggest concern.

    The main Greenhouse gases present in the Earth's atmosphere are carbon dioxide, water vapor, Nitrous Oxides, Sulfates, and Methane.  However, those of the highest concentration are carbon dioxide.  For the moment disregarding any synergistic effect created by further evaporation of water into water vapor due to the excess heat trapped by the carbon dioxide, it is important to note how critical carbon dioxide is in the heating of the Earth.  Radiation that comes from the sun is allowed in, through the atmosphere, to the surface of the Earth.  It then bounces back toward space, but is captured and reflected back down by the Greenhouse gases.  Over time, as the concentration of these gases increases, the warming effect is multiplied, and the temperature of the Earth increases.  Global warming is actually a natural phenomenon, without which the earth would be a colder place.  Over thousands of years the earth has developed natural cycles that change over long periods of time. Scientists are worried that our presence has effected theses cycles and could alter the way the world works.

    Ice cores from the artic have been used to estimate the amount of historical carbon dioxide in the atmosphere, and accurate measurements of carbon dioxide levels have been kept since 1958.  As shown by these graphs, the concentration of carbon dioxide increased steadily but only slightly from 800 AD until about the 1800's.  However, with the occurrence of the industrial revolution in the early 1900's, levels increased almost exponentially.  So, too, did the temperature of the Earth.  Not only has the aggregate amount of carbon dioxide increased, but the rate at which it is being produced has increased exponentially.
                               Source: http://yosemite.epa.gov/oar/globalwarming.nsf/content/climate.html

      Since 1958, US researchers have measured the amount of carbon dioxide in the atmosphere at the Mauna Loa volcano laboratory in Hawaii. Researchers at the laboratory found an increase in carbon dioxide to a record level of 378 parts per million (ppm). What astonishes them most is the fact that the rate at which carbon dioxide has been emitted has increased as well. The research was carried out by the US government's Climate Monitoring Diagnostics Laboratory, part of the National Oceanic and Atmospheric Administration (NOAA). The laboratory's director, Dr. Pieter Tans, says, “That variations in the growth rate year by year can be explained by natural factors, for example, changes in the rate at which plants and the oceans soak up carbon dioxide. But he and his colleagues conclude that the steady rise overall can be attributed to man-made emissions of carbon.”

   In fact, in the next 20 years we will have doubled the amount of carbon dioxide since the industrial age.  However, with all the current information, scientists are only able to speculate as to the real effects of global warming.  Today, scientists use complicated computer models (like STELLA) to predict these effects based on the complex interactions of Earth's physical systems.  These complicated computer models need large amounts of input in order to simulate earth’s natural cycles.  This means that there could many possible outcomes which make the effects of global warming variable in size and force.  As a result, the magnitude of global warming and its effects produce many questions and uncertainties.  Today scientists are able measure current changes to natural events around the world accurately, and they have been very vocal about making these effects known to the world.

    Another important aspect of global warming is the relative quantity of carbon dioxide being emitted by the different parts of the world.  It has long been understood that the developed world, and more specifically the United States, has contributed the largest amount of Greenhouse gases to the atmosphere. The graph below shows this trend.  It is therefore vitally important that people here start gaining a better understanding of how one would go about changing the way we live, so as to cut down on the amount we contribute to this global phenomenon.  Chapel Hill, a town within the country with the highest emissions, is acting as a frontrunner for the Carbon Reduction project, making an effort to conceptualize the problem and outline solutions in a practical manner.
 

    Whereas much controversy has arisen over what would actually happen should Earth's average temperature increase by one or two degrees Celcius, it is clear to most scientists that global warming has begun altering our planet.  Rainfall anomalies in the United States, glacial retreats in Peru, ice cap melting in polar regions, and coral bleaching across equatorial oceans and seas are all clear signals that we need to act, and act now.

    Click here for a description of the possible effects of global warming.  In addition, we have provided more information about North Carolina's efforts to curb global warming, as well as Chapel Hill's previous legislation decisions.
 

Here are some articles about the effects of Global Warming:
Antarctic Glaciers Show Retreat
CO₂ Emissions Put Coral at Risk
The World's Taps Are Running Dry

For more information:
CRed Project from Spring 2004 regarding Carolina North: http://www.unc.edu/%7Emccarty/globalclimatechange.htm
EPA Global Warming Information: http://yosemite.epa.gov/oar/globalwarming.nsf/content/climate.html
Intergovernmental Panel on Climate Change: http://www.ipcc.ch/