Methane and You

Introduction:

            Methane, our most abundant hydrocarbon, often called natural gas, is a very efficient absorber of infrared radiation. Although its present atmospheric concentration is only 1.68 parts per million, its high rate of increase is of great concern. If, as expected, the atmospheric concentration of methane doubles in the next 25 years, the cumulative global warming effect of methane and the other greenhouse gases will equal that of carbon dioxide.

            Analysis of old ice shows that methane concentration held steady for the last 10 000 years. About 300 years ago the level began to rise and 100 years ago it began to soar. The current annual rate of increase of methane (1 %) is greater than that of carbon dioxide (0.4 %).

            There is no clear consensus among scientists about why the concentration of methane is rising so rapidly. Much of it comes from the breakdown of plant material in the absence of oxygen, as in swamps and inside cattle. However, much methane is also produced through certain human activities which have increased as the human population has grown.

Methane Facts and Questions:

1. Below is a list of methane sources in order of volume produced, from highest to lowest:

            wetlands, swamps

            cattle

            tropical rainforest and savanna grassland burning

            natural gas and mining

            human made dumps and landfills

            termites and other insects

            oceans

            lakes

            tundra

Which of the above have increased because of human activities and/or human population growth?

Have any decreased with human activity? Explain your answers.

2. The natural gas that some burn in their homes for heating and cooking is about 90 % methane. It has been released by drilling into trapped underground pockets of gas. What happens to the methane that escapes during drilling or in pipe leakage while being transported to homes?

3. Microorganisms that are capable of digesting wood live in the guts of termites. One of their waste products is methane. As deforestation has continued around the world, the supply of rotting wood has increased. This abundant food source has expanded the termite population. A significant part of the increase in atmospheric methane is thought to be due to this source. List the following statements in order starting with the first and showing which causes which:

            Increased atmospheric methane, Increased termite population, Increased human population, Deforestation, Need for agricultural land area, Wood-digesting microorganisms, Broken wood dead roots, Methane as digestive waste

4. Rice plants are composed of hollow tubes that grow out of waterlogged soil. Methane produced by bacteria in the muck finds its way into the atmosphere through the rice tubes. Have you ever seen bubbles rising from the muddy bottom of a lake? What could the gas be and where do you think it came from?

5. The permafrosts of tundra regions and of polar ocean sediments contain vast quantities of methane trapped by frozen water molecules. What may happen if, partly due to the increase of atmospheric methane, the environment gets warmer and the frozen water melts?

6. Construct a chart with time on the horizontal, methane concentration on the left vertical axis and world population on the right vertical axis. Using the data below, make two line graphs on your chart, one showing world population and the other showing the increase in atmospheric methane.