Researchers studying the effects of climate change in Antarctica say shrinking sea ice means bad news for emperor penguins: an 81 percent reduction in the number of breeding pairs by 2100.

"We conclude that climate change is a significant risk for the emperor penguin," says the study, published this week in the journal Global Change Biology.

Scientists caution, however, that the study contains large uncertainties because climate model forecasts disagree on exactly how the ice will respond to a warming world.

The study projects the number of emperor penguin breeding pairs in a colony at Terre Adélie will drop from roughly 3,000 to as few as 500 by the turn of the century. But researchers point out that if the ice does shrink at their current home, the penguins may simply move to regions with more favorable sea ice conditions.

Emperor penguins are the largest of the species and breed and raise their young almost exclusively on the ice, biologists say.

"If the sea ice breaks up too early, this will cause massive breeding failures because the chicks will not yet have the waterproof plumage that will allow them to swim in the water," said study co-author Stephanie Jenouvrier, a biologist at the Woods Hole Oceanographic Institution in Massachusetts.

"If they happen to be in the water, they will die," Jenouvrier said.

Decreasing amounts of sea ice may also have a ripple effect on the penguin's food supply, including fish, shrimp and krill.

The study's authors relied on simulations from 20 computer climate models that assume moderate growth in greenhouse gas emissions.

A vast majority of climate scientists believe humans have been steadily warming the atmosphere and oceans since the industrial revolution, leading to "widespread melting of snow and ice and rising global average sea level."

"People say the temperature may increase by two degrees, so what?'" Jenouvrier told ABC News. "But changes that may seem small to humans are not small to species, and may affect the entire ecosystem."