Weather stations like this one collect information throughout the world. But are some more reliable than others?

Courtesy Peter Essick/Aurora/Getty Images

Global Warming Skeptics' Arguments

Since global warming became a major issue, climatology has become a hot-button scientific field. Weather stations throughout the world collect data to help scientists create computer models that help them track global climate change.

Some people simply don't believe that the Earth is undergoing a global warming trend or climate change. Others believe in global warming and climate change, but don't believe that people are responsible. The skeptics who don't believe in global warming at all are the ones who most vehemently attack weather data, the analysis of the climatologists and the predictions of the models.

Anti-global warming skeptics say the placement of some weather stations in urban areas may produce inaccurate measurements. According to them, the data are being corrupted by the urban heat island, an effect produced by cities' transportation, large amounts of heat-absorbing asphalt, and high concentrations of carbon dioxide coming from the many homes and businesses in high-population areas.

Global warming skeptics also believe the models used to predict Earth's future under global warming are unreliable. They feel that while the sun, clouds, gases, glaciers and oceans are responsible for weather, so, too, are other factors, including some we don't currently understand. According to global warming skeptics, computer models are merely a guess at what will happen on Earth in the future -- something climatologists don't deny -- and an arguably poor guess at that. After all, if we can't accurately predict the weather a week from now, how can we predict the global climate in 100 years?

Others don't believe we're experiencing a global warming trend at all. The annual temperature between 1998 and 2007 actually decreased, despite the 4 percent increase in carbon dioxide in the atmosphere during that same period. They also point out that, while the Northern Hemisphere has warmed, the Southern Hemisphere has actually cooled. "Global warming was supposed to actually be global, not hemispheric," says skeptic -- and Executive Director of the Natural Resources Stewardship Project -- Tom Harris [source: Canada Free Press].

These same skeptics find fault in the historical data used to graph things like glacial loss and hurricane frequency. Although weather data, like temperature, have been actively collected since 1850, it wasn't until the relatively recent access to detailed weather satellite photography that scientists were able to see changes in the Greenland ice shelf that global warming believers say is in such danger. Skeptics ask: How can we know how long it's been receding?

Perhaps the meteorological event most often used by global warming skeptics as a counterargument is the Medieval Warm Period. Around the 9th to 14th centuries, regions around the world experienced an increase in temperatures, similar to what we see today [source: National Oceanic and Atmospheric Administration]. Following this period, the Earth experienced a Little Ice Age where global temperatures cooled. It is conceivable that the Earth is currently experiencing something similar to this, skeptics say. Their point is, we simply don't know enough about long-term weather systems to say for certain one way or the other.

The skeptics of human-caused (anthropogenic) global warming don't dismiss global warming outright, they just don't believe that human activity is responsible. Learn more about their beliefs on the next page.