WASHINGTON (AP) — Spurred chiefly by China, the United States and India, the world spewed far more carbon pollution into the air last year than ever before, scientists announced Sunday as world leaders gather to discuss how to reduce heat-trapping gases. The world pumped an estimated 39.8 billion tons (36.1 billion metric tons) of carbon dioxide into the air last year by burning coal, oil and gas. The team projects that emissions of carbon dioxide, the main heat-trapping gas from human activity, are increasing by 2.5 percent this year. The scientists forecast that emissions will continue to increase, adding that the world in about 30 years will warm by about 2 degrees Fahrenheit (1.1 degrees Celsius) from now. Chris Field, a Carnegie Institution ecologist who heads a U.N.