In 1986, a panel of 150 scientists from eleven countries issued a report warning that human activities such as automobile use, the production of energy from burning fossil fuels, and deforestation could cause global temperatures to rise by intensifying the earth’s greenhouse effect.
An essential component of the earth’s climate, the greenhouse effect is the warming process that results from the atmospheric presence of heat-trapping gases such as water vapor, carbon dioxide, and nitrous oxide. Much of the solar energy that reaches the planet is absorbed by oceans and land masses, which in turn radiate the energy back into space. However, small concentrations of water vapor and other “greenhouse gases” convert some of this energy to heat and either retain it or reflect it back to the earth’s surface. This “trapped” energy creates a blanket of warm air around the earth that moderates global temperatures and climate patterns. Without greenhouse gases, the earth would exist in a perpetual ice age.
The scientists who maintained in the 1980s that human activities could amplify the greenhouse effect were elaborating on a nineteenthcentury theory proposed by Swedish chemist Svante Arrhenius. In 1896, Arrhenius hypothesized that the carbon dioxide produced from the burning of coal and other fossil fuels would cause global temperatures to rise by trapping excess heat in the earth’s atmosphere. But the global warming theory did not capture the world’s attention until 1988, when James Hansen, an atmospheric scientist and director of the Goddard Institute for Space Studies at NASA, testified before a U.S. Senate committee that the “evidence is strong” that human-made pollutants were raising world temperatures. If temperatures continued to rise, he warned, the earth would face catastrophic climate changes that would adversely affect the environment and human health.
Initially, most climate researchers were skeptical about Hansen’s warning. It was true that carbon dioxide levels had increased by about 30 percent since the mid-1700s, when the Industrial Revolution began; it was also true that the average world temperature had risen by one degree Fahrenheit (F) during the twentieth century—the largest increase of any century during the past millenium. Yet the earth’s climate had been prone to fluctuations over the past several hundred years, many climatologists maintained. The one degree temperature change could be attributed to the natural variability of the planet’s weather.
As scientists conducted more climatological research, however, data supporting Arrhenius’s global warming theory mounted. In 1995, the Intergovernmental Panel on Climate Change (IPCC), a United Nations subcommittee comprising more than two thousand scientists, asserted that human activities were partly responsible for rising global temperatures. In its ensuing assessment reports, the IPCC also predicted that carbon dioxide levels could double by the year 2100, causing temperatures to increase from 2 to 10.4 degrees F. Such a temperature change would likely bring a greater incidence of floods, droughts, heat waves, wildfires, hurricanes, and other forms of extreme weather—which in turn could cause an increase in storm-related deaths, infectious diseases, and economic crises, analysts warned. The weather of the 1990s—the hottest decade on record— seemed to bear these warnings out. As environmental journalist Ross Gelbspan points out, the year 1998 “began with a January ice storm that left four million people without power in Quebec and northern New England. For the first time, rainforests in Brazil and Mexico actually caught fire. The summer brought killer heat waves in the Middle East, India and Texas, where residents suffered through a record 29 consecutive tripledigit days.” The following year was even worse, contends Gelbspan: “1999 saw a record-setting drought in the Mid-Atlantic states. . . . A heat wave in the Midwest and northeastern U.S. claimed 271 lives. Hurricane Floyd visited more than $1 billion in damages on North Carolina. A super-cyclone in eastern India killed 10,000 people. That winter, mudslides and rains in Venezuela claimed 15,000 lives. Unprecedented December windstorms swept northern Europe, causing more than $4 billion in damages.”
Even before these extreme weather events occurred, a United Nations conference met in Kyoto, Japan, to discuss how to respond to the potential risks posed by global warming. In December 1997, UN negotiators approved an agreement requiring thirty-eight industrialized nations to reduce their greenhouse gas emissions by 6 to 8 percent below 1990 levels by the year 2012. Developing countries, which are poorer and less able to reduce greenhouse gases without straining their economies, were exempted from the emissions reduction requirement but were given voluntary standards as goals. Emmissaries signing this treaty—known as the Kyoto Protocol—must obtain approval from their own governments to render it a binding agreement. A Clinton administration official signed the Kyoto Protocol in 1998, but the U.S. Senate voted in 1999 to reject any climate change treaty that does not require poor nations to reduce their own greenhouse gases.
Although American environmentalists continue to advocate for the ratification of the Kyoto Protocol, critics argue that the treaty would hurt the economy and lower U.S. living standards. Cutting down greenhouse gas emissions would require the energy and industrial sectors to adopt expensive pollution-reducing technology—or to slow down their rate of production. The ensuing reduction in energy and goods would in turn raise gas, food, and housing costs, anti-Kyoto forecasters predict. Moreover, economists warn that adopting the protocol would place U.S. businesses at a competitive disadvantage if developing nations remained exempt from pollution-reducing requirements. Faced with the high cost of reducing emissions, some U.S. companies would relocate to developing countries, resulting in job losses for Americans.
Heeding these warnings from critics of the Kyoto Protocol, President George W. Bush officially withdrew U.S. support for the treaty in 2001. In a speech he delivered a few months after taking office, Bush also announced that he had formed a Cabinet-level working group to review the most up-to-date information on global warming and climate change. The working group contacted the highly respected National Academy of Sciences, which issued a report stating that the increase in carbon dioxide levels since the Industrial Revolution was largely due to human activity. However, noted Bush, “the Academy’s report tells us that we do not know how much effect natural fluctuations in climate may have had on warming. We do not know how much our climate could, or will change in the future. We do not know how fast change will occur, or even how some of our actions could impact it.”
Bush’s speech reflects the skepticism that some scientists have about the global warming theory. Some climatologists maintain that the higher incidence of severe weather during the 1990s was not necessarily linked to higher greenhouse gas levels or higher global temperatures. Moreover, as several researchers point out, the IPCC’s predictions about global warming are largely based on computer-generated climate simulations, which have proved to be unreliable. Global temperature readings taken on the ground, from satellites, and from weather balloons often contradict the projections of the computer simulations. For example, no warming of the lower troposphere (the atmosphere between 5,000 and 28,000 feet) has been recorded, even though climate simulators indicated that tropospheric warming should have already occurred due to increased carbon dioxide levels. Skeptical scientists contend that the fallibility of the IPCC’s predictions raises serious doubts about the projected severity of global warming.
In June 2002, Bush publicly stated that humanity would be able to adjust to global warming. Some researchers are even more optimistic, maintaining that a warmer earth will result in lusher forests, increased food production, lower energy costs, and improved human health. Many scientists and environmentalists, however, fear that unchecked global warming will lead to dramatic increases in extreme weather that could uproot regional populations, augment the spread of infectious diseases, and disrupt worldwide economies. At Issue: Is Global Warming a Threat? examines the continuing controversy over the relationship between greenhouse gases and climate change.