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As you learn more about climate change, you.ll need to understand some key terms. Let's start off by looking at some significant ones.

Climate Change

Climate includes all the elements of weather. When we speak of climate change we are referring to changes in the climate as a whole, not just one single element of the weather. Global climate change, therefore, refers to the changes in all the interconnected weather elements of the Earth. Scientists know that the world's climate has changed naturally over millions of years. Many scientists strongly believe that humanity's actions are also changing the world's climate.

Greenhouse Effect

This is the process of trapping heat in the atmosphere by gases known as greenhouse gases. These are namely water vapour, carbon dioxide, methane, and nitrous oxides. Many scientists believe the Earth has a natural greenhouse effect and an enhanced greenhouse effect (caused by human actions).

Global Warming

Global warming refers to natural or human-induced increases in the average global temperature of the atmosphere near the Earth.s surface. Many scientists believe that humans are contributing to global warming through the creation of greenhouse gas sources and the reduction of greenhouse gas sinks.

Ozone Layer

Many people confuse a decrease in ozone with the term, greenhouse effect. In fact, these are two separate phenomena. It is true that in the lower atmosphere, ozone is a pollutant. We often see this as smog in big cities like Toronto. But in the stratosphere, ozone provides an essential shield against ultraviolet radiation. The highest concentrations of ozone are in the stratosphere - about 90%. The ozone layer absorbs or screens out about 99% of all ultraviolet radiation. Scientists have noticed a depletion of ozone over Antarctica. Although this has been referred to as a hole, it is better to say that a relative depletion inconcentration has taken place. Many scientists believe that a reduction in ozone concentrations is the result of cloroflourocarbons, which have been used as propellants in hair sprays and deodorants, and in air-conditioning units and refrigeration.

Scientists are finding more links between the greenhouse effect and the ozone layer. But remember that the enhanced greenhouse effect refers to a build up of greenhouse gases in the lower atmosphere. This may lead to global warming. A decrease in ozone in the stratosphere, however, may lead to an increase in ultraviolet radiation arriving at the Earth's surface.


Key Words

Climate Change
Greenhouse Effect
Global Warming
Ozone Layer

Sources

Climate Change brochure,
Clean Nova Scotia, 1999

Environment, Second Edition,
Berg et al. 1998

   

    Last Modified: 2004-12-10