Global Climate Change

Global Climate Change: Overview
Global climate change is a change in the long-term weather patterns that characterize the regions of the world. The term "weather" refers to the short-term (daily) changes in temperature, wind, and/or precipitation of a region (Merritts et al. 1998). Weather is influenced by the sun. The sun heats the earth's atmosphere and its surface causing air and water to move around the planet. The result can be as simple as a slight breeze or as complex as the formation of a tornado (see above). Photo: The first tornado captured by the National Severe Storms Laboratory Doppler radar in Union City, Oklahoma on May 24, 1973. Photo courtesy of National Oceanic and Atmospheric Administration.

Some of the sun's incoming long wave radiation is reflected back to space by aerosols. Aerosols are very small particles of dust, water vapor, and chemicals in Earth's atmosphere. In addition, some of the sun's energy that has entered Earth's atmosphere is reflected into space by the planet's surface. The reflectivity of Earth's surface is called albedo. Both of these reflective processes have a cooling affect on the planet.

The greenhouse effect is a warming process that balances Earth's cooling processes. During this process, sunlight passes through Earth's atmosphere as short-wave radiation. Some of the radiation is absorbed by the planet's surface. As Earth's surface is heated, it emits long wave radiation toward the atmosphere. In the atmosphere, some of the long wave radiation is absorbed by certain gases called greenhouse gases. Greenhouse gases include carbon dioxide (CO₂), Chlorofluorocarbons (CFC's), methane (CH₄), nitrous oxide (N₂0), tropospheric ozone (O₃), and water vapor. Each molecule of greenhouse gas becomes energized by the long wave radiation. The energized molecules of gas then emit heat energy in all directions. By emitting heat energy toward Earth, greenhouse gases increase Earth's temperature. Note that the warning mechanism for the "greenhouse effect" is NOT exactly the same as the warning mechanism of greenhouse walls. While greenhouse gases absorb long wave radiation then emit heat energy in all directions, greenhouse walls physically trap heat inside of greenhouses and prevent it from escaping to the atmosphere.

The greenhouse effect is a natural occurrence that maintains Earth's average temperature at approximately 60 degrees Fahrenheit. The greenhouse effect is a necessary phenomenon that keeps all Earth's heat from escaping to the outer atmosphere. Without the greenhouse effect, temperatures on Earth would be much lower than they are now, and the existence of life on this planet would not be possible. However, too many greenhouse gases in Earth's atmosphere could increase the greenhouse effect. This could result in an increase in mean global temperatures as well as changes in precipitation patterns.

Image of a diagram showing the solar radiation and IR Emission from Earth. Please have someone assist you with this. When weather patterns for an area change in one direction over long periods of time, they can result in a net climate change for that area. The key concept in climate change is time. Natural changes in climate usually occur over; that is to say they occur over such long periods of time that they are often not noticed within several human lifetimes. This gradual nature of the changes in climate enables the plants, animals, and microorganisms on earth to evolve and adapt to the new temperatures, precipitation patterns, etc.

The real threat of climate change lies in how rapidly the change occurs. For example, over the past 130 years, the 7mean global temperature appears to have risen 0.6 to 1.2 degrees Fahrenheit (0.3 to 0.7 degrees Celsius). These temperatures changes are depicted in the graph below from the EPA's Global Warming site. The increasing steepness of the curve suggests that changes in mean global temperature have occurred at greater rates over time. Further evidence suggests that future increases in mean global temperature may occur at a rate of 0.4 degrees Fahrenheit (0.2 degrees Celsius) each decade. Figure: Changes in global temperature (degrees Fahrenheit) from 1861 to 1996. Graph adapted from image courtesy of the U.S. EPA.

Image of a graph showing the Global Temperature Changes from 1861-1996. Please have someone assist you with this. The geological record--the physical evidence of the results of processes that have occurred on Earth since it was formed--provides evidence of climate changes similar in magnitude to those in the the above graph. This means during the history of the earth, there have been changes in global temperatures similar in size to these changes. However, the past changes occurred at much slower rates, and thus they were spread out over long periods of time. The slow rate of change allowed most species enough time to adapt to the new climate. The current and predicted rates of temperature change, on the other hand, may be harmful to ecosystems. This is because these rates of temperature change are much faster than those of Earth's past. Many species of plants, animals, and microorganisms may not have enough time to adapt to the new climate. These organisms may become extinct. Figure: Global temperature (degrees F) changes from 1861 to 1996. Graph adapted from image courtesy of the U.S. EPA.

Home ..|.. Teacher Pages ..|.. Modules & Activities

HTML code by Chris Kreger
Maintained by ETE Team
Last updated November 10, 2004

Center for Educational Technologies, Circuit Board/Apple graphic logo, and COTF Classroom of the Future logo are registered trademarks of Wheeling Jesuit University.