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The Facts on Global Climate Change :: April 16, 2007

Frequently Asked Questions

| FAQ's | Potential Impacts of Climate Change | R&D Initiatives | Legislation | Learn More |

What is climate change?

"Climate" is the long-term average of a region's weather patterns. "Climate change" is the name used to describe changes in those patterns. Changes will be different depending on the region, but may include changes to average temperatures (up or down), changes in season length (e.g. shorter winters), changes in rain and snowfall patterns, and changes in the frequency of intense storms.

What is the difference between climate change and global warming?

These two terms are often used interchangeably, but they do have slightly different meanings. The term "global warming" refers specifically to increases in average global temperature. The rise in temperature is what is driving climate change. Some people feel the term "global warming" seems to imply that the only change will be an increase in temperatures. The reality is far more complicated, since rising temperatures can impact everything from rainfall patterns to sea levels to storm activity. In some areas, temperatures may even fall. The term "climate change" is better at capturing this complexity.

What causes climate change?

The simple answer is rising global temperatures. There is no dispute among the world's scientists that the earth is warming. The earth has warmed by about 1.4 degrees Fahrenheit over the past 100 years, and the rate of change has accelerated in recent decades.

But what is causing average temperatures to rise?

Most climate scientists agree that rising temperatures are being caused by increasing concentrations of greenhouse gases (GHGs) in the earth's atmosphere. Most of the increase in GHG concentrations is the result of emissions associated with human activities, such as burning fossil fuels (oil, coal, and natural gas), cutting down forests, and certain agricultural activities. Most climate scientists, including those working on the Intergovernmental Panel on Climate Change, believe that human activities are the principal causes of these changes.

Is climate change related to the hole in the ozone layer?

Climate change and the ozone hole are really separate issues, but they do have some characteristics in common. Both problems are caused by the buildup of chemicals in the atmosphere that result from human activity. Another relationship is that some of the ozone-friendly gases that were introduced to replace ozone-depleting gases have turned out to be potent greenhouse gases. In other words, part of our solution to the ozone problem is contributing to the climate change problem.

What is "the greenhouse effect"?

The greenhouse effect is the result of certain gases in the earth's atmosphere called "greenhouse gases" (or GHGs). These GHGs allow incoming solar radiation to pass through the Earth's atmosphere, but prevent most of the outgoing infrared radiation from the surface and lower atmosphere from escaping into outer space.

This is a natural process and it has kept the Earth's temperature about 60 degrees Fahrenheit--warmer than it would be otherwise. Without GHG's, most of the sun's energy would reflect back into space, and the Earth would be a frozen iceball with average temperatures hovering around zero degrees Fahrenheit. Thus, most of life as we know it depends on the natural greenhouse effect.

Climate change is the result of an intensifying greenhouse effect. As human activities release ever more greenhouse gases into the atmosphere, GHGs trap more and more of the energy that would otherwise escape. This raises global temperatures and changes the climate.

What are the major greenhouse gases?

Some greenhouse gases such as carbon dioxide occur naturally and are emitted into the atmosphere through both natural processes and human activities. Other greenhouse gases (e.g., fluorinated gases) are created and emitted solely through human activities. The principal greenhouse gases that enter the atmosphere because of human activities are:

  • Carbon Dioxide (CO2): Carbon dioxide enters the atmosphere through the burning of fossil fuels (oil, natural gas, and coal), solid waste, trees and wood products, and also as a result of other chemical reactions (e.g., manufacture of cement). Carbon dioxide is also removed from the atmosphere (or "sequestered") when it is absorbed by plants as part of the biological carbon cycle.
  • Methane (CH4): Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from livestock and other agricultural practices and by the decay of organic waste in municipal solid waste landfills.
  • Nitrous Oxide (N2O): Nitrous oxide is emitted during agricultural and industrial activities, as well as during combustion of fossil fuels and solid waste.
  • Fluorinated Gases: Hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride are synthetic, powerful greenhouse gases that are emitted from a variety of industrial processes. Fluorinated gases are sometimes used as substitutes for ozone-depleting substances (i.e., CFCs, HCFCs, and halons). These gases are typically emitted in smaller quantities, but because they are potent greenhouse gases, they are sometimes referred to as High Global Warming Potential gases ("High GWP gases").

What are the major sources of greenhouse gases?

Most GHGs have both natural and human sources. However, it is the human sources of these gases that are causing the greatest concern, because they are responsible for the incremental increases in atmospheric concentration. The most significant human sources of greenhouse gases are:

  • Fossil fuels: Fossil fuels include oil, coal and natural gas, and when they are burned they release carbon dioxide into the atmosphere. Humans depend heavily on these fuels to power everything from our cars and trucks to our electrical power plants.
  • Deforestation: Healthy forests store a great deal of carbon in the form of biomass. When forests are destroyed, often to create new cropland or by wildfires, it releases large amounts of carbon dioxide.
  • Agriculture: Some agricultural operations release large amounts of GHGs. For example, rice farming and cattle ranching both release significant amounts of methane.

What can we do about climate change?

People usually talk about two categories of solutions to address climate change: mitigation and adaptation.

Mitigation strategies try to address the problem at its source by reducing overall greenhouse gas emissions and/or removing such gases from the atmosphere. Mitigation discussions often focus on how we generate and use energy. For example, nuclear power and renewables (e.g. wind, solar, geothermal) do not generate any GHGs in the process of producing electrical power. Biomass is also considered a renewable source because even though it emits CO2 when burned, the same amount of CO2 is reabsorbed from the atmosphere by next year's crop, creating net zero emissions. Even fossil fuel burning industries, like coal-fired power plants, are experimenting with mitigation by separating the CO2 before it is released into the atmosphere so it can be safely stored in geologic formations deep underground. Increasing energy efficiency is another important mitigation strategy since it allows people to accomplish the same amount with less energy. Finally, forest protection and reforestation projects are another focus, since forests store large amounts of carbon.

Adaptation strategies, by contrast, are focused on changing the way we do things so that we can continue to live comfortably in a warming world. Adaptation strategies focus on everything from the way we grow crops (e.g. developing heat-resistant strains of grain), to the way we use water (e.g. learning to use it more efficiently), to how we build coastal cities (e.g. building sea-walls or creating buffer zones). Adaptation is important because scientists have determined that even if we were to cease all emissions tomorrow, a certain amount of climate change will continue to occur for decades, or even centuries to come.

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