What Is Global Warming?
A definition of global warming—a gradual increase in the Earth’s temperatures—seems to be simple to document and easy to understand. The scientific evidence also seems to be straight forward—average global temperatures are rising year after year. Even so, the controversy, mixed with politics, has been fierce. It has taken the nation's premier science policy body, the United States National Research Council, to try to set the record straight. In June 2006, they published a paper stating that they had confidence the studies showed that the Earth at present is the hottest it has been in the last 400 years, and perhaps even hotter than in the last 2,000 years. They based their statement on studies showing that the average global surface temperature over the Earth has increased by approximately 0.5-1.0°F (0.3-0.6°C) in just the last one hundred years. (See graph Projected Changes in Global Temperature.) Furthermore, they state that the last one-hundred year increase is the greatest in the last 1,000 years. Some scientists are predicting an even greater increase in the twenty-first century. Additionally, many experts go even further by attributing the increase of greenhouse gases (primarily carbon dioxide and methane) in the Earth's upper atmosphere caused by human burning of fossil fuels, industrial activity, farming, and deforestation as the activities causing this temperature increase.
How has global warming affected the oceans?
Many find it hard to believe that in their lifetime the level of the ocean has risen significantly. (See graph Sea Level Rise over the Last Century.) After all, the beach seems to look pretty much like it did last year; even so oceanographers have data that show it really has risen over 10 centimeters (about 4-5 inches) in the last one hundred years. If the attached graph was extended an additional 100 hundred years, presuming the increase to be the same as the last century, the data would show at least another 10 centimeters totaling about one half foot. This doesn't seem like much, although it would adversely affect many coastal areas around the world. However, an addition complication is occurring: the ice at the poles is melting faster than new ice is forming. In a paper by the U.S. Center for Atmospheric Research it was shown that ice is declining on average 7.8 percent per decade, much faster than the 2.5 percent that was predicted. This phenomenon is heavily affecting pole climate, especially the formation of icebergs. If all of the ice melted, an unlikely scenario, it could raise the ocean level by over 20 feet, but that would be a slow process, perhaps 500 to 1000 years. Visualize a wall 20 feet high and then stand in the beach and transfer that thought to the ocean. Those living near would be covered by a 20 foot wall of water. Most of South Florida, for instance, is under 20 foot elevation, not to mention what it would do to a city like New Orleans. All of this won't affect the present generation, but future generations will be affected.
How has the carbon dioxide levels been affected?
A major player in the controversy is the amount of carbon dioxide in the air. (See carbon dioxide graph.) Plants use carbon dioxide and give off oxygen as a "waste product." Animals, on the other hand, use this discarded oxygen in respiration and give off carbon dioxide as a "waste product.” The graph shows that our atmosphere has increased about 100 parts per million in the last 250 years, mostly the years since the Industrial Revolution. The increase might be even greater if it was not for the phytoplankton in the oceans using some of the excess carbon dioxide.
Is there a relationship between increased burning of fossil fuels and the increase in temperature and carbon dioxide? Most scientists who have studied the phenomenon would say yes. However, there are those who say the increase is not caused by mankind's activity but by a natural swing in environmental norms. Looking back in geological time at the cycles that have occurred before, there have been times when temperatures on the Earth have changed, warmer and colder, but most of these cycles have been measured in thousands of years. The phenomenon of change occurring in hundreds of years, while not unique, is exceptional and highly distinctive.
The gradual warming of our earth is a fact, whether it is natural or mankind caused. What action is taken about the fact is being played out in national arenas around the world. The crossroads are here now; which road we take, to try to change the process or just let it happen, will determine what our grandchildren and their children will have to endure.
References
U.S. Environmental Protection Agency
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