As concern over global warming has grown, many governments worldwide have looked for ways to curb the amount of greenhouse gases their countries emit, either by imposing mandatory curbs or pursuing voluntary measures.

The gases are known as greenhouse gases because they trap energy and heat, generated by the sun, in Earth's atmosphere, making the planet warmer, like a greenhouse for plants.

According to the EPA, since 1990, fluoride-containing gas emissions have grown by 58 percent due to substituting these gases in products like hairspray or spray paint for chlorofluorocarbons -- gases that deplete the ozone layer.

With the situation increasingly confirmed in scientific studies, international organizations and foreign governments have launched an array of programs and initiatives to tackle the issue.

The Kyoto Protocol
One major international agreement to reduce greenhouse gas (GHG) emissions is the Kyoto Protocol to the United Nations Framework Convention on Climate Change.

The agreement, signed in 1997 and put into effect by 141 participating nations in 2005, aims for a percentage reduction of the GHG levels produced in 1990 by signatory countries.

The emissions goals "range from an 8 percent reduction for the European Union (or its individual member states) to a 10 percent increase allowed for Iceland. The target for the United States is 7 percent below 1990 levels," according to a report by the U.S. Energy Information Administration.

Some countries that have become protocol signatories -- the Eastern European and former Soviet states, including Russia in November 2004 -- have seen their economies slow since 1990. This means less industry, fewer carbon dioxide-producing power plants, and, therefore, reduced overall GHG emissions.

As for the United States, the EPA said in 2004 that total GHG emissions there are up 16 percent, well above target Kyoto protocol levels. The United States has signed the Kyoto protocol the U.S. Senate never ratified it. The Bush administration says the United States would be at a disadvantage on the world market because large developing countries, including India, China and Brazil, are not yet required to meet specific emissions targets.

However, some observers say measures independent of an overall, international scheme will not work. "The real concern is that the U.S. hasn't gone with anything particularly significant in the absence of it [Kyoto]," said John Topping, president of the nonprofit Climate Institute.

But the United States has insisted that it will not ratify the Kyoto protocol unless emissions targets are established for developing countries like Brazil, China, and India. (Click here for more on U.S. policy.)

The United States accounts for 24 percent of all CO2 emissions, the main greenhouse gas, according to a May 2006 World Bank report. European Union countries account for 10 percent. China, the world's second polluter after the United States, and India are quickly catching up, the World Bank said. China's CO2 emissions have increased by 33 percent between 1992 and 2002, and India's CO2 emissions have increased 57 percent in the same period, according to the report.

China, India and Brazil are pursuing voluntary efforts at reducing GHG emissions in order to take economic and developmental needs into consideration. With rapidly growing economies and populations, they are building new infrastructure, and in the process, using new, sustainable, and comparatively affordable technology that often are more environmentally friendly.

China, India and Brazil
One of the main environmental concerns in China, especially after recent dust storms covered Beijing in haze, is air quality.

With China's population is set to explode in the next couple of decades, the World Resources Institute, an environmental think tank based in Washington, D.C., has projected its emissions of carbon dioxide could grow by 118 percent in the coming decades.

In 1998, the government established the State Environmental Protection Agency to implement national environmental policies, collect data and offer technical national and international advice on environmental matters, according to the U.S. Energy Information Administration.

To tackle nagging pollution problems, China passed the Cleaner Production Promotion Law in 2002, which created pilot pollution control programs in 10 major cities.

India, meanwhile, is the second most populous nation on Earth and the fifth largest emitter of greenhouse gases, contributing to almost 6 percent of the world's total GHGs, according to the World Resources Institute.

Efforts in India to curb greenhouse gases accompany its goal of bringing electricity to everyone in the country. Many rural farmers and others rely on diesel-powered generators for electricity, or simply go without.

But the major issue for India's government was whether it would be more economically sensible to extend the main power grid from cities into rural areas, or to simply build wind-powered generators for rural areas which are off the main grid.

In the end, India decided on wind power. In fact, said Topping, "There an extensive investment in wind energy, so extensive they're back-ordered to 2008."

In Brazil, meanwhile, a program using the fuel additive ethanol has been in place since the oil crisis in the 1970s, when the price of gasoline skyrocketed and the price of sugar went down. The program, started under then-president Ernesto Geisel, provided a more stable market for Brazil's sugar cane growers but also initiated a cleaner burning fuel.

Voluntary efforts in other countries
One European country that has exceeded its Kyoto protocol goal of emissions reduction is Germany, a prosperous country that has undergone significant development, especially in the East, since 1990 -- the base year for emissions goals under the Kyoto protocol.

The German government voluntarily set a goal of 21 percent emissions reduction from 1990 levels, and as of May 2005, was 2.1 percent away from its goal "in large part due to the necessary and large-scale modernization process of East German industry in the early 1990s," Simon Marr of the American Institute for Contemporary German Studies at Johns Hopkins University wrote in July 2005.

Germany also has implemented alternative energy measures, such as installing solar panels on some government buildings, and switching from coal power stations to renewable and cleaner-burning energy sources, such as natural gas and biomass power.

Mexico City, meanwhile, has one of the largest and most sprawling populations of any city in the world, and has had a long struggle to rein in pollution from vehicles, on par with major American cities like Los Angeles and New York City.

Efforts to curb GHG emissions there have coincided with initiatives to shorten job commutes, such as the June 2005 launch of the Metrobus system, which runs on dedicated lanes and helps reduce pollution in the city of 18 million people.

The city also has worked to replace older-model taxis, which had been held to lower emissions standards, by paying taxi owners cash for older vehicles, according to the Climate Group.

"Once all of these vehicles have been replaced it is estimated that daily emissions from taxis will be reduced by about 31 percent," the group said.

The U.S. government, though not tied to international treaties, has partnered with foreign governments and corporations in many countries, primarily in Latin America, to come up with ways to generate energy that will reduce GHG emissions.

Aside from helping countries like Bolivia and Ecuador harness hydroelectric power, one project established by the International Utility Efficiency Partnerships Inc. is the EcoSecurities NovaGerar Landfill Gas-to-Energy Project in Brazil.

This project captures the methane given off by two landfills in Rio De Janeiro and uses it to generate energy for the local power grid.

The IUEP estimates that, aside from the methane emissions stopped, over 20 years the project will have reduced emissions of CO2 by 7 million tons.

Another IUEP project under consideration that does not deal with power generation is the Pozo del Tume Carbon Sequestration project, which is a re-foresting, logging and land-preservation project in Argentina.

The project would work at developing sustainable methods of re-planting forests while at the same time allowing cattle grazing.

For this project, the IUEP estimates a reduction of 2 million tons of carbon dioxide over 70 years, and illustrates how environmental and economic efforts often go hand-in-hand.

-- By A.C. Valdez, Online NewsHour