In recent weeks, a broad range of data — like reports on new residential construction and small business confidence — have beaten analysts’ expectations. Initial claims for jobless benefits, often an early indicator of where the labor market is headed, have dropped to their lowest level since May 2008. And prominent economics groups say the economy is growing three to four times as quickly as it was early in the year, at an annual pace of about 3.7 percent.

But the good news also comes with a significant caveat. Many forecasters say the recent uptick probably does not represent the long-awaited start to a strong, sustainable recovery. Much of the current strength is caused by temporary factors. And economists expect growth to slow in the first half of 2012 to an annual pace of about 1.5 to 2 percent…

There are two reasons for the renewed pessimism. First, economists say that temporary trends increased growth in the fourth quarter and may not continue into next year. Second, the economy faces significant headwinds in 2012: some from Europe’s long-lingering sovereign debt crisis, and some from domestic cutbacks beyond the control of President Obama, whose campaign would like to point to a brightening economic picture, not a darkening one. Even the Federal Reserve is predicting that the unemployment rate will remain around 8.6 percent by the time voters go to the polls in November.