Two U.S. scientists say it's not a question of "if" there will be nearly ice-free summers in the arctic but "when," and sooner than many think.

National Oceanographic and Atmospheric Administration scientists James Overland and Muyin Wang say several different methods for predicting when the arctic will be nearly ice free in the summer show it could happen before 2050 and possibly within the next decade or two.

"Rapid arctic sea ice loss is probably the most visible indicator of global climate change; it leads to shifts in ecosystems and economic access, and potentially impacts weather throughout the northern hemisphere," Overland said in a NOAA release Friday.

"Early loss of arctic sea ice gives immediacy to the issue of climate change," he said.

The various methods for predicting ice loss includes observed trends, historical records and computer modeling of global climate.

"There is no one perfect way to predict summer sea ice loss in the arctic," Wang said. "So we looked at three approaches that result in widely different dates, but all three suggest nearly sea ice-free summers in the arctic before the middle of this century."

Although yielding different time frames, the multiple approaches still suggest future sea ice loss will be within the first half of the 21st century, with a possibility of major loss within a decade or two, the researchers said.

"Some people may interpret this [difference] to mean that models are not useful. Quite the opposite," Overland said. "Models are based on chemical and physical climate processes and we need better models for the arctic as the importance of that region continues to grow."