单项选择题

A "greenhouse effect" will raise the earth’’s temperature enough by the year 2100 to cause dramatic climate changes, increase sea levels and disrupt food production, United States scientists said this week. 　　The earth’’s atmosphere is heating at a rate that could mean temperature rises of two degrees centigrade by the middle of the 21st century and five degrees centigrade by the year 2100, according to a report issued by the US government’’s Environmental Protection Agency (EPA). 　　"Substantial increases in global warming may occur sooner than most of us would like to believe," the EPA said. 　　The agency said the first effects might be felt as early as 1990, because temperatures would be rising more than seven times faster each decade between now and the year 2100 than they had been for the past 100 years. 　　"Temperature increases are likely to be accompanied by dramatic changes in precipitation and storm patterns and a rise in global average sea level," the EPA report said. 　　"As a result," the agency said, "agricultural conditions will be significantly altered, environmental and economic systems potentially disrupted." 　　The EPA report said the burning of fossil fuels was directly responsible for most of the atmosphere build-up of carbon dioxide but the current concentration is so great that even a worldwide ban on the use of such fuels would delay the warming effect for only a few years. 　　"A warmer climate will raise sea levels by heating and expanding the world’’s oceans and causing glaciers to melt," the EPA said. 　　The agency estimated that sea levels could rise anything between 48 to 380 cm in the next 120 years. 　　"An increase of even 48 cm could flood or cause storm damage to many of the major ports of the world, disrupt transportation networks, alter underwater ecology systems and cause major shifts in land development patterns." 　　One study cited in the report suggested that if the average global temperature rose by 2.5 degrees centigrade, regional climatic conditions might be similar to those during the last interglacial period 120,000 years ago. 　　During this period, oceans were five to seven metres higher than today’’s, flooding the shores of Europe and western Siberia and making Scandinavia an island. 　　The agency said that while the warming trend could have some beneficial effects, such as reducing heating costs and improving climate and growing seasons in some parts of the world, there would be difficulty in redirecting national economies to adapt to the new climate patterns. 　　The EPA said it seemed unlikely that the nations of the world would reach a consensus on step to reduce carbon dioxide emissions. Instead, it urged more research on the greenhouse effect and stressed the need for better planning to cope with the changes the warming trend is expected to produce. Which of the following is included in the EPA report