What are Greenhouse Gases, What Causes Global Warming?

By Henrylito D. Tacio

Manila, 23 July 2009, The Philippines is among the countries facing great risk if the trend in global warming, caused by carbon dioxide emission, is not reversed, an international conservation group warned.

“The Philippines is extremely vulnerable to the ravages of climate change. Food and fresh water shortages, receding coastlines and an increase in political and economic turmoil is the bleak picture that climate change paints for the country,” the World Wide Fund for Nature said in a statement.

Global warming refers to an increase in average global temperatures, which in turn cause climate change. “To completely understand why global warming happens, it is important to know that our atmosphere, which is made up of gases such as nitrogen, oxygen, and carbon dioxide as well as water vapor, has a profound influence on Earth’s surface temperature,” explains the Worldwatch Institute, an independent research organization based in Washington, D.C.

So-called greenhouse gases (GHG) such as carbon dioxide and methane absorb heat, thus reducing the amount that escapes back to space. “As the atmosphere absorbs heat energy," Worldwatch notes, “it warms the oceans and the surface of the Earth. This process is called the greenhouse effect. Without this effect, the Earth's atmosphere would average about 50 degrees Fahrenheit colder, making it impossible to sustain life on Earth. Rising levels of heat absorbing greenhouse gases such as carbon dioxide in the atmosphere will increase global temperatures (called global warming).”

“Intensive climate research and monitoring over the past few years has given scientists greater confidence in their understanding of the causes and effects of global warming,” said Dr. Klaus Töpfer, former executive director of the United Nations Environment Program.

“There is no longer any doubt that the Earth’s climate is changing,” said Dennis Tirpak, chair of a recent climate change conference held in England.  “Globally, nine of the past 10 years have been the warmest since records began in 1861. Rising greenhouse gases are affecting rainfall patterns and the global water cycle.”

Carbon dioxide - released when we burn fossil fuels to produce electricity, use gasoline in our cars, or switch on our natural gas stoves for cooking - has been singled out as the biggest factor in changing the Earth’s climatic conditions.

Noel Grove, author of Air: An Atmosphere of Uncertainty which appeared in National Geographic, explained the role of carbon dioxide in this manner: “Like panels of glass in a greenhouse, carbon dioxide allows most solar radiation to penetrate the atmosphere but prevents part of the heat radiated by land and bodies of water from escaping into space.  As carbon dioxide accumulates, enough heat may be trapped to gradually warm the atmosphere.”

Since the beginning of the Industrial Revolution an estimated 350 billion tons of carbon dioxide have been released through the burning of fossil fuels.

Methane is another GHG cited for global warming.  It is a gas created naturally as a waste product of anaerobic bacteria (living with little or no oxygen).  These bacteria produce methane gas in waterlogged soils and wetlands, but also in human-produced environment like rice paddies.

“An estimated 19 percent of the world’s methane production comes from rice paddies,” said Dr. Alan Teramura, botany professor at the University if Maryland in the United States.  “As populations increase in rice-growing areas, more rice – and more methane – are produced.”

Aside from rice paddies, the other top sources of methane gas in the atmosphere are wetlands (20.2 percent), ruminants or cud-chewing animals like cattle (14 percent), biomass fires, such as burning forests(9.7 percent), oil and natural gas pipeline leaks (7.9 percent), termites (7 percent), coal mining (6.2 percent), landfills (6.2 percent), animal wastes (5 percent, and sewage (4.4 percent).

Scientists claim that one molecule of methane gas from decaying rice paddies is about 10,000 times more efficient in heating up the planet Earth than one molecule of carbon dioxide emitted by a gasoline engine.

Another GHG which is almost exclusively produced by human activity is the chlorofluorocarbons (CFCs).   These gases were first synthesized about 85 years ago, entering commercial use soon afterwards, first in a refrigerant gas and then in aerosol propellants. 

CFC are approximately 15,000 times more efficient as greenhouse gas than carbon dioxide, scientists say.  Once in the atmosphere, CFCs linger for 50 to 100 years or more.  But what is alarming is that CFCs destroy ozone and prevent it from reforming.  (The ozone layer is a protective shield that surrounds Earth at an altitude of 15 to 30 kilometers.)

Nitrogen compounds, the primary pollutants that contribute to air pollution, also augment in increasing the planet’s average temperature.  The most common of these compounds are nitrogen oxide and nitrogen dioxide. 

As with other pollutants, nitrogen compounds come primarily from automobiles and electric power-generating plants.  These compounds play a major role in the production of secondary air pollution that create photochemical smog.  They also contribute to the development of acid rain.

“Dealing with (global warming) will not be easy.  Ignoring it will be worse,” said the Nobel-winning Intergovernmental Panel on Climate Change said in a statement.  “Without effective action, climate change is going to be larger and more difficult to deal with than we thought.”

Think globally; act locally, so they say. “We can pledge to do our part to conserve energy and pollute less,” the Worldwatch suggests. “Whether at home, on our commute to work or school, or at the store, there are things we can do to lessen our impact on climate change.”

“The issue is not stopping global warming - this will almost certainly not be possible within most of our lifetimes,” notes Worldwatch’s Christopher Flavin. “Rather, the challenge is to slow the production of greenhouse gases immediately, so as to avoid the most sudden and catastrophic climate changes. If trends continues unabated, only radical, draconian measures would be sufficient to save the climate later on.”