ByJohn S. McClenahen Although during the last month it has trimmed its U.S. GDP projection by a tenth of a percentage point to 3%, Waltham, Mass.-based Global Insight Inc., along with President Bush's Council of Economic Advisers, remains among the most bullish 2003 forecasters. Indeed, the economic forecasting firm expects the U.S. "to begin recovering in earnest" this year from the 2001 recession and the subsequent protracted period of slow growth. The recovery will accelerate in 2004, the firm predicts, with GDP growing at an inflation-adjusted rate of 4.5%. In contrast, Merrill Lynch & Co., New York, for example, foresees just 2.3% GDP this year and 3.4% next year. Global Insight's forecast is based on several significant assumptions. Among them: Beginning late this month or early in March the U.S. leads a short and successful military campaign to unseat Saddam Hussein; oil prices initially spike above $40 per barrel but then retreat as it becomes evident hostilities won't cut off supplies; and the war adds $50 billion to federal spending during the next six calendar quarters.