The Global Environment
Earth image from NASA's Apollo 17

Problems Facing Our Earth

A discussion of many global environmental issues can be found at the United Nations Environment Programme pages.

Stratospheric Global Ozone Depletion

• Most of the Earth's ozone is contained in a layer of the atmosphere that is approximately 10-25 miles (15-40 kilometers) above the Earth's surface, in the stratosphere. Depletion of this layer will lead to higher UVB levels, which in turn will cause increased skin cancers and cataracts and potential damage to some marine organisms, mammals, plants, and plastics.

• The United Nations, through the Montreal Protocol, has established an agreement for the phaseout of many ozone depleting substances. At least 160 nations have signed the accord.

• Ozone depleting substances (ODS) are stable in the atmosphere. After release they migrate to the troposphere where ultraviolet light destroys the original molecule, releasing its chlorine and bromine which then react with ozone.

• Some common ODS with US EPA deadlines.

• Some of the reasons for the delay in changing to HFCs.

  • Existing refrigeration systems cannot use HFCs and will thus become obsolete.

  • Newer systems capable of using HFCs will be more expensive.

  • Industrial producers require time to develop the capacity to produce the new substances.

• The United States stopped production of CFCs, halons, carbon tetrachloride, and methyl chloroform on December, 31, 1995.

• Details from US EPA. Details of the Montreal Protocol from the UN's Ozone Secretariat.

Images from NASA, animation by B. T. Ray

• Unfortunately our past excesses will be around for many years to haunt us. The atmospheric lives of some common ozone depleting chemicals exceed 100 years.

Global Warming

• Global warming, or the greenhouse effect, is caused by certain chemicals that impede the exit of solar radiation reflected from the Earth's surface (see the Air Pollution notes). This process is natural, but human activity has increased the effect the past century or more.

• Excessive CO₂ emissions account for about 85 percent of the greenhouse gasses emitted in the US.

• Global CO₂ levels are shown below for the past three centuries.

• It is estimated by scientists studying this problem that the global average temperature will increase about 2 to more than 6°F during the next century. If this is true, and it probably is, there will be far reaching negative effects on Earth.

  • Significant climate changes

  • A rise in sea level, threatening many large coastal cities

  • Loss of many coastal wetlands

  • Increasing areas of desert

  • Increased levels of insect pests threatening crops

  • Reduced agricultural production

Deforestation

• Deforestation is the result of our increasing population, and the demands it places on our environment.

• How fast are we losing habitat?

  • According to Greenpeace over 75% of the planet's original primary forests have already been destroyed or degraded. And, the destruction is increasing, not slowing.

  • Current estimates are that we are losing about 60,000 square miles of tropical forest each year. That is about two football fields per second.

  • Well over 90% of Brazils east coast forests are gone. Every 9 seconds, another acre is lost. It has been estimated that one half of all species on Earth reside in the Brazilian forests, something between 2 and 30 million species.

  • In Canada, it takes 12 seconds to loose an acre of forest. That's 5 acres per minute.

  • Russia, which possesses 22% of all forests on Earth, is rapidly accelerating its forest industry.

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The rainforest sounds on this page were recorded by a Greenpeace member. Download a larger (1MB) rainforest sounds file, also from Greenpeace.