Greenhouse Gases

The numerous public forums that discuss environmental issues and the ever-increasing political debates about the damage humans are doing to the planet always include some mention of greenhouse gases. Scientists and scholars toss the term about like everyone knows exactly what it means, but most people probably don't really understand what greenhouse gases are and how they can be harmful.

Greenhouse gases (GHG) are gaseous components in the atmosphere that contribute to the "greenhouse effect", the heating of the Earth by means of a similar effect produced by the glass panes of a greenhouse. Greenhouse gases allow light from the sun to enter the atmosphere surrounding the Earth. When that sunlight strikes the planet, some of it is reflected back toward space as infrared radiation, or heat. The GHGs in the atmosphere trap the heat, but over time the amount of energy sent from the sun to the Earth's surface should be about the same as the amount of energy radiated back into space, leaving the temperature of the planet's surface pretty constant. However, it is a documented scientific fact that global temperatures have been steadily rising for decades.

Some GHGs, such as water vapor, carbon dioxide, methane, ozone, and nitrous oxide, occur naturally to some extent in the atmosphere. Human activities add to the levels of these naturally occurring gases, and many of those activities are benign and don't have significant effects on the environment. But the political debate over GHGs focuses on certain human activities that increase the concentrations of GHGs in ways that threaten the environment, and research has stepped up dramatically in recent years to determine whether or not humans should be trying to limit those activities.

Although opinions are mixed about exactly how the Earth's climate responds to GHGs, most researchers are in agreement that greenhouse gases from industry and agriculture have played a major role in global warming. Just the increase in the population of the planet has to have had some effect on the GHGs in the atmosphere, because more people are breathing out carbon dioxide, and deforestation to make room for those people has resulted in fewer trees producing oxygen. The burning of fossil fuels also leads to higher concentrations of carbon dioxide, which constitutes about 76% of all the greenhouse gases in the Earth's atmosphere. Most of the increase in carbon dioxide has occurred in the last 50 years. Measurements from Antarctic ice core samples have shown that carbon dioxide concentrations stayed pretty stable for about 10,000 years, but began rising in the mid-20th century.

Methane gas accounts for about 13% of the GHGs in the atmosphere. Since 1750, the amount of methane gas in the atmosphere has doubled, and some scientists say that amount could double again by 2050. Each year nearly 500 tons of methane are added to the air by coal mining, drilling for oil and natural gas, landfill emissions, wetland changes, and pipeline losses. New style fully vented septic systems, Livestock and paddy rice farming, CFCs used in refrigeration systems, and halons in fire suppression systems are also sources of atmospheric methane. Most GHGs take a very long time to leave the atmosphere, but methane stays in the atmosphere for only 10 years. However, it traps 20 times more heat than carbon dioxide.

Nitrous oxide, primarily used as "laughing gas", an inhaled anesthetic, is released naturally from oceans and by bacteria in soils. Nitrous oxide gas production has risen by more than 15% since 1750, and now makes up approximately 6% of the GHGs in the atmosphere. Each year about 7-13 million tons are released into the atmosphere by using nitrogen-based fertilizers, disposing of human and animal waste in sewage treatment plants, automobile exhaust, and other sources not yet identified. Nitrogen-based fertilizer use has doubled in the past 15 years. The nitrous oxide being released into the atmosphere today will still be trapped in there 100 years from now.

Since the beginning of the Industrial Revolution, the concentrations of many GHGs in the Earth's atmosphere have steadily increased. In 1992, the United Nations held a summit meeting in Rio de Janeiro called the Conference on Environment and Development to develop a treaty aimed at reducing emissions of greenhouse gases in order to combat global warming. The treaty, called the United Nations Framework Convention on Climate Change (UNFCCC) is legally non-binding and sets no mandatory limits on GHG emissions for individual nations, but the countries who signed the treaty agreed to develop their own plans and schedule for limiting emissions. The FCCC entered into force on March 21, 1994, with the stated objective being "to achieve stabilization of greenhouse gas concentrations in the atmosphere at a low enough level to prevent dangerous anthropogenic interference with the climate system".

The treaty included provisions for eventually setting mandatory emissions limits, with the primary update being the Kyoto Protocol, which was established in 2005. Carbon dioxide, methane, nitrous oxide, and three groups of fluorinated gases are the subject of the Kyoto Protocol. Part of the reason for establishing the Kyoto Protocol was the increased sense of urgency felt by many scientists as newer data is found to support the theory of "global warming", which could have disastrous effects upon the Earth if changes are not implemented right now.

The world's leading authority on global warming is the Intergovernmental Panel on Climate Change (IPCC), a United Nations-sponsored organization consisting of 2500 scientists from around the world. The IPCC has predicts that global warming will have severe impact on human health, natural ecosystems, agriculture, and coastal communities if steps are not taken immediately to reverse the increasing concentrations of GHGs in the Earth's atmosphere. The IPCC has concluded by consensus that "The balance of evidence suggests a discernible human influence on global climate". That "human influence" is the increased levels of greenhouse gases being released into the atmosphere, and stronger steps must be taken toward reversing the trend before it is too late to repair the damage.