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Global Climatic Change Primer

H.J. Helikson and P.H. Jones

AN EXPLANATION OF THE GREENHOUSE EFFECT

In a greenhouse, light energy penetrates the greenhouse windows and falls upon the plants and furnishings inside. When it hits a surface, the light energy becomes heat energy, which radiates in all directions but which is unable to penetrate the greenhouse windows and escape into the atmosphere. For this reason, on a sunny day the air inside a greenhouse is warmer than the air outside. The greenhouse effect is a very important, naturally-occurring phenomenon within Earth's atmosphere too. It works in the following manner.

1. Light energy penetrates Earth's atmosphere as short-wave radiation.
2. This energy is absorbed by Earth's surface and changed into heat energy.
3. This heat energy is radiated off into the atmosphere surrounding Earth, as long-wave radiation.
4. The greenhouse gas molecules [carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), and water vapor (H₂O vapor), which naturally exist in the troposphere, absorb the long-wave, heat radiation which hits them on its way back to outer space.
5. The limited quantity of greenhouse gases in the troposphere allows some heat radiation to escape into the stratosphere and beyond.
6. Greenhouse gas molecules give off the heat energy they capture within the troposphere. Without the greenhouse gases, the average temperature of Earth's troposphere would be below freezing (5 degrees F, -15 degrees C).

The concern over global climatic change has arisen due to the fact that the atmospheric quantities of CO₂, CH₄, and N₂O are increasing relatively rapidly in comparison to what has occurred in the past. In addition, man-made gases like chlorofluorocarbons (CFC's), which have heat-holding capacities 15,000 times greater than CO₂, are also being added to the troposphere. An increased quantity of greenhouse gases in the troposphere decreases the chances of heat energy escaping the troposphere just like an increased number of blockers on a football field decreases the chances of a successful two-point conversion. These greenhouse gas "guards" in the troposphere make the earth behave like a greenhouse. An increase in Earth's average atmospheric temperature and all of the changes within the global ecosystem that this increase could instigate is the reason people are concerned about the global climatic change phenomenon.

GREENHOUSE EFFECT PREDICTIONS

No one knows for sure exactly how much or what kind of changes could occur on Earth due to global climatic change. Scientists do suggest an increasing likelihood of the following as greenhouse gas concentrations in Earth's atmosphere change.

• an average warming of Earth by 3-8 degrees F.
• a change in weather patterns with an increase in weather extremes (floods and droughts).
• a melting of sea ice and an average sea level rise leading to coastal flooding.
• the proliferation of crop pests and diseases over more agricultural croplands.
• an increased rate of species extinction.

SOME COMMONLY ASKED QUESTIONS

Human activities can directly influence the speed at which global climatic change might occur. In order to better understand how we as individuals impact the concentrations of greenhouse gases within our atmosphere, the following questions and answers are provided for your reference.

Where do greenhouse gases come from?

Information is presented in Table 1 on the four greenhouse gases considered to have the greatest potential for affecting global climatic change.

How much fossil fuel energy is consumed in Florida annually?

In 1988, approximately 3,000,000,000,000,000 Btu of energy were consumed in Florida. Taking into consideration the state's population of 12,503,800, each Florida resident accounted for an expenditure of 239,927,062 Btu of energy (approximately 1,900 gallons of gasoline). This energy was used in the following manner:

• Transportation - 35%
• Commercial - 23%
• Residential - 27%
• Industrial - 15%

This energy was supplied from the following sources:

• Petroleum - 52%
• Natural Gas - 10%
• Coal - 23%
• Other - 15%

This energy consumption in Florida emitted 422,100,000 pounds of CO₂ into the atmosphere in 1988. And with Florida's population growing at nearly 1,000 per day coupled with the over 40 million tourist who visit annually, Florida will continue to be a major contributor of greenhouse gases. The size of Florida's coastline and the amount of revenue generated by the state's agricultural production increase the potential economic and environmental impact which might occur from coastal flooding and/or inland drought. Therefore, Floridians should have a great deal of interest in promoting the development of and establishing programs for global warming mitigation strategies.

Why is everyone talking about the rain forest?

Growing plants and trees are very important to the balance of CO₂ in Earth's atmosphere. They utilize CO₂ during the photosynthesis process and produce oxygen. These biomass materials provide a CO₂ storage sink while they are alive. Approximately 25 million acres of tropical rain forests are lost each year. The destruction of this biomass accounts for almost 20 percent of the anthropogenic CO₂ emitted into the atmosphere every year. Although an enormous area of land would be required for reforestation to make a substantial net CO₂ reduction, it might be the least expensive alternative. In addition, reforestation efforts would assist with biodiversity maintenance, watershed protection, and non-point source pollution reduction.

Given the scope of the problem, can anything be done to make a difference?

The United States National Academy of Sciences published a report in 1991 entitled "Policy Implications of Greenhouse Warming." This report recommends the following set of energy conservation measures:

• strict automobile fuel efficiency standards.
• improved lighting and appliance efficiencies.
• support for mass transit.
• increased federal funds for energy research and development.

The current Bush administration strategy includes the following actions:

• phase out ozone-depleting compounds.
• curb sulfur dioxide output (Clean Air Act).
• plant 1 billion trees per year.
• improve forestry management.
• adopt energy-efficient standards for appliances.
• fund energy research and development including alternative energy resources.

It is the rate of global climatic change that may be the most important factor in determining the effect of global climatic change on both natural and man-made systems: the faster the climatic change, the harder it will be to adapt effectively. Lifestyles in Florida tend to consume a great deal of energy. The amounts of energy consumed annually are large because of the daily decisions we as individuals make regarding the use of natural and monetary resources. Energy and environmental savings can accrue from one individual using energy more efficiently 365 days a year (Table 2 ).

Tables

Table 2.

GLOSSARY

anthropogenic: of, relating to, or influenced by the impact of man on nature.

atmosphere: the gaseous mass or envelope surrounding a celestial body in space. 

Btu: British thermal unit, the quantity of heat required to raise the temperature of one pound of water by one degree Fahrenheit. 

chlorofluorocarbons: any of various chemical compounds containing carbon, fluorine and chlorine used chiefly as lubricants and refrigerants and making resins and plastics. 

fossil fuel: fuels ultimately derived from living things. 

greenhouse gas: a gaseous molecule at standard temperature and pressure which has a molecular structure able to absorb heat. 

mitigation: the act of making less harsh or severe. 

photosynthesis: the process by which chlorophyll-containing cells in green plants use the energy of light to synthesize carbohydrates from carbon dioxide and water. 

sink: a body or process that acts as a storage device or disposal mechanism. 

stratosphere: the part of the atmosphere above the troposphere. 

troposphere: the lowest region of the earth's atmosphere, characterized by temperatures that decrease with increasing altitude.

Footnotes

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