"One of the reasons that emissions haven't really gone up exponentially over the past 100 years in the United States is because of the fact that now perhaps two-thirds of the energy is supplied by relatively clean fuels," he says. "Also, particularly in the past 40 years or so, pollution controls have reduced the amount of emissions released into the atmosphere. If not for cleaner fuels and emissions controls, the amount of sulfur emissions today would easily be three or four times what they are now."
Husar estimates that global sulfur emissions in 1850 were 1.2 million metric tons, just 1.7 percent of his 1990 estimate of 71.5 million metric tons. Beginning in 1913, there was a leveling off and then a decline during World War I. The early years of the Great Depression saw a marked decrease in emissions, but that soon changed with World War II. There was a continuous increase in the post-war years, with a drop in 1981-83, corresponding to declining oil demand during the global recession.
Since 1970, U.S. emissions show a general decline. No coincidence, according to Husar, who notes the passage of the Clean Air Act in 1977 and the subsequent Clean Air Act of 1990, which requires that all power plants not exceed a certain amount of emissions.
As the 1990s began, the United States and Canada were emitting a combined estimated 15 million metric tons of sulfur, compared with approximately 22 million metric tons by China.
"The data clearly show that while North American and in some cases, European, emissions have been leveling off, rapid increases are occurring in China," Husar says.
Sulfur emissions are the prime ingredient in the creation of acid rain. While the United States and Canada contested each o
Contact: Tony Fitzpatrick
Washington University in St. Louis