Efforts to Control Global Warming

    Responding to the challenge of controlling global warming will require fundamental changes in energy production, transportation, industry, government policies, and development strategies around the world. These changes take time. The challenge today is managing the impacts that cannot be avoided while taking steps to prevent more severe impacts in the future.

    Reducing emissions of greenhouse gases, also called greenhouse gas mitigation, is a necessary strategy for controlling global warming. There are two major approaches to slowing the buildup of greenhouse gases. One is to reduce the consumption of fossil fuels, thereby reducing greenhouse gas emissions. The other is to keep carbon dioxide out of the atmosphere by storing the gas or its carbon component somewhere else, a strategy known as carbon sequestration or carbon capture.

A. Carbon Capture

   One way to keep carbon dioxide emissions from reaching the atmosphere is to preserve and plant more trees. Trees, especially young and fast-growing ones, soak up a great deal of carbon dioxide from the atmosphere and store carbon atoms in new wood. Worldwide, forests are being cleared at an alarming rate, particularly in the tropics. In many areas, there is little regrowth as land loses fertility or is changed to other uses, such as farming or housing developments. In addition, when trees are burned to clear land, they release stored carbon back into the atmosphere as carbon dioxide. Slowing the rate of deforestation and planting new trees can help counteract the buildup of greenhouse gases.

    Carbon dioxide gas can also be captured directly. Carbon dioxide has traditionally been injected into depleted oil wells to force more oil out of the ground or seafloor. The same process can be used to store carbon dioxide released by a power plant, factory, or any large stationary source. For example, since 1996 this process has been used at a natural gas drilling platform off the coast of Norway. Carbon dioxide brought to the surface with the natural gas is captured, compressed, and then injected into an aquifer deep below the seabed from which it cannot escape. In most cases, the process of carbon capture would also involve transporting the gas in compressed form to suitable locations for underground storage. Deep ocean waters could also absorb a great deal of carbon dioxide, although the environmental effects may be harmful to ocean life. The feasibility and environmental effects of these options are under study by international teams.

B. Energy Sources 

  The total worldwide consumption of fossil fuels is increasing by several percent per year. However, energy use around the world is slowly shifting away from fuels that release a great deal of carbon dioxide toward fuels that release somewhat less of this heat-trapping gas.

   Wood was the first major source of energy used by humans. With the advent of the Industrial Revolution in the mid-1700s, coal became the dominant energy source. By the mid-1800s oil had replaced coal in dominance, fueling the internal combustion engines that were eventually used in automobiles. By the 1900s, natural gas began to be used worldwide for heating and lighting. In this progression, combustion of natural gas releases less carbon dioxide than oil, which in turn releases less of the gas than do either coal or wood. However, a reversal of this trend may be seen as reserves of oil are used up. Other fuel sources such as tar sands (also known as oil sands) are beginning to be utilized. Producing oil from tar sands involves extraction and refining processes that release carbon dioxide. In addition, the relative abundance of coal reserves in countries such as China and the United States may lead to a new upswing in the use of coal for generating electricity. Newer technologies for cleaner coal-burning power plants may help offset the effects.

    Significant reductions in carbon dioxide emissions can only be achieved by switching away from fossil-fuel energy sources. Nuclear power plants release no carbon dioxide at all, but nuclear energy is controversial for reasons of safety, security, and the high costs of nuclear waste disposal. Solar power, wind power, and hydrogen fuel cells also emit no greenhouse gases. These energy sources can be practical, low-pollution alternatives to fossil fuels. Other alternatives include fuels made from plants, such as biodiesel (made from used and new vegetable oil) and ethanol (a plant-based gasoline additive). Use of these fuels can help reduce total carbon dioxide emissions from automobiles. The hybrid electric vehicle (HEV), which uses both an electric motor and a gasoline or diesel engine, emits less carbon dioxide than conventional automobiles (see Electric Car). See also World Energy Supply.

C. International Agreements

    International cooperation is required for the successful reduction of greenhouse gases. The first international conference addressing the issue was held in 1992 in Rio de Janeiro, Brazil. At the United Nations Conference on Environment and Development, informally known as the Earth Summit, 150 countries pledged to confront the problem of greenhouse gases by signing the United Nations Framework Convention on Climate Change (UNFCCC). To date, more than 180 nations have ratified the UNFCCC, which commits nations to stabilizing greenhouse gas concentrations in the atmosphere at a level that would avoid dangerous human interference with the climate. This is to be done so that ecosystems can adapt naturally to global warming, food production is not threatened, and economic development can proceed in a sustainable manner.

    The nations at the Earth Summit agreed to meet again to translate these good intentions into a binding treaty for emissions reductions. In 1997 in Japan, 160 nations drafted an agreement known as the Kyōto Protocol, an amendment to the UNFCCC. This treaty set mandatory targets for the reduction of greenhouse gas emissions. Industrialized nations that ratify the treaty are required to cut their emissions by an average of 5 percent below 1990 levels. This reduction is to be achieved no later than 2012, and commitments to start achieving the targets are to begin in 2008. Developing nations are not required to commit to mandatory reductions in emissions. Under the Kyōto rules, industrialized nations are expected to take the first steps because they are responsible for most emissions to date and have more resources to devote to emissions-reduction efforts.

   The protocol could not go into effect unless industrialized nations accounting for 55 percent of 1990 greenhouse gas emissions ratified it. That requirement was met in November 2004 when Russia approved the treaty, and it went into force in February 2005. By the end of 2006, 166 nations had signed and ratified the treaty. Notable exceptions included the United States and Australia.

    In 1998 the United States—then the world’s single largest contributor to greenhouse gas emissions—became a signatory to the Kyōto Protocol. However, in 2001 U.S. president George W. Bush withdrew support for the treaty. He claimed that the treaty’s goals for reducing carbon dioxide emissions would be too costly and would harm the U.S. economy. He also claimed the treaty put an unfair burden on industrialized nations. Opposition to the treaty in the United States was spurred by the oil industry, the coal industry, and other enterprises that manufacture or depend on fossil fuels. These opponents claimed that the economic costs to carry out the Kyōto Protocol could be as much as $300 billion, due mainly to higher energy prices. Proponents of the Kyōto Protocol believed the costs would prove more modest—$88 billion or less—much of which would be recovered as Americans switched to more efficient appliances, vehicles, and industrial processes.

      The Kyōto Protocol, which expires in 2012, is only a first step in addressing greenhouse gas emissions. To stabilize or reduce emissions in the 21st century, much stronger and broader action is required. In part this is because the Kyōto provisions did not take into account the rapid industrialization of countries such as China and India, which are among the developing nations exempted from the protocol’s mandatory emissions reductions. However, developing nations are projected to produce half the world’s greenhouse gases by 2035. Leaders of these nations argue that emissions controls are a costly hindrance to economic development. In the past, prosperity and pollution have tended to go together, as industrialization has always been a necessary component of an economy’s development. Whether or not an economy can grow without increasing greenhouse gas emissions at the same time is a question that will be critical as nations such as China and India continue on the path of industrialization.

    In 2007 the European Union (EU) took the initiative in coming up with a new international plan to address global warming. At a “green summit” held in March, the 27 nations of the EU reached a landmark accord that went above and beyond the Kyōto Protocol in setting targets to reduce greenhouse gas emissions. The agreement set ambitious targets for the EU overall, but goals for individual EU nations and rules of enforcement were to be determined through additional negotiations.

     In the accord EU leaders agreed to reduce emissions by 20 percent from 1990 levels by 2020—or by as much as 30 percent if nations outside the EU joined in the commitments. They also agreed that renewable sources of energy, such as solar and wind power, would make up 20 percent of overall EU energy consumption by 2020 (an increase of about 14 percent). The accord also called for a 10 percent increase in the use of plant-derived fuels, such as biodiesel and ethanol. In addition to these targets, EU leaders agreed to work out a plan to promote energy-saving fluorescent light bulbs, following the example of countries such as Australia and Chile that are officially phasing out less-efficient incandescent light bulbs.