Anchorage ? Two groups of scientists are suggesting a sliver of hope for the future of polar bears in a warming world.

A sow polar bear rests with her cubs on pack ice in the Beaufort Sea in northern Alaska in this undated file photo. If the world dramatically changes its steadily increasing emissions of greenhouse gases, global warming can be slowed enough to prevent a total loss of critical summer sea ice for the polar bears, according to a new study in the journal Nature released Wednesday.

A study published online Wednesday rejects the often used concept of a “tipping point,” or point of no return, when it comes to sea ice and the big bear that has become the symbol of climate change woes. The study optimistically suggests that if the world dramatically changed its steadily increasing emissions of greenhouse gases, a total loss of critical summer sea ice for the bears could be averted.

Another research group projects that even if global warming doesn’t slow — a more likely near-future scenario — a thin, icy refuge for the bears would still remain between Greenland and Canada.

A grim future for polar bears is one of the most tangible and poignant outcomes of global warming. Four years ago, federal researchers reported that two-thirds of the world’s polar bear habitat could vanish by mid-century. Other experts foresee an irreversible ice-free Arctic in the next few years as more likely.

The new study, which challenges the idea of a tipping point, says rapid ice loss could still happen, but there’s a chance that the threatened bears aren’t quite doomed.

“There is something that can be done to save polar bears,” said lead author Steven Amstrup, the former senior polar bear scientist for the U.S. Geological Survey in Alaska. “The problem is not irreversible.”

His research, published in Nature, shows there’s a steady relationship between greenhouse gas emissions, sea ice and polar bear habitat. As emissions rise, sea ice and polar bear habitat decline. But unlike previous research, there’s no drop-off tipping point in Amstrup’s models.

Essentially, until all sea ice is gone permanently in the summer, there is still a chance to prevent the worst case, if global warming is stopped in time, Amstrup’s research shows.

“Such a tipping point would mean that future reductions in greenhouse gas emissions would do little to save the polar bear,” said Amstrup, who is now chief scientist for the conservation group Polar Bears International. “It seems clear that if people and leaders think that there’s nothing they can do, they will do nothing.”