Europe's automakers' association ACEA has confirmed that the industry's six-year decline ended last year, reporting a 5.7-percent increase in car sales in 2014 to 12.5 million vehicles.

That was the continent's first positive full-year result since 2007, with December marking the 16th straight month of growth.

Despite the upbeat performance reported Friday, carmakers were cautious heading into 2015 amid new economic uncertainty.

Carlos Ghosn, the CEO of Nissan and Renault, said this week at the Detroit Motor Show that he expects European growth this year to be slow, around 1 percent to 2 percent.

Jeff Schuster, executive vice president of forecasting for industry consultancy LMC Automotive, says the tamped-down forecasts are due in part to deflation concerns.