"We need good hypotheses," Dr. Alley said, "and he's given us one."

"It's hard to find something he hasn't touched," says Dr. Alley.

Dr. Alley said he considered this a reasonable assessment.

But "there weren't any big ice sheets in the Eemian," said Dr. Alley.

"What the research shows is that there are switches as well as dimmers in Earth's system," Dr. Alley said.

"The harder you push, the more likely you are to cross a threshold," Dr. Alley said.

Dr. Alley also said the shrinkage might be related to a general warming of the earth.

"If that turns out to be true," Dr. Alley said, "that's something we're going to have to worry about in the future."

Dr. Alley said there was a potential that "putting more fresh water into the Atlantic will cause things to change in a hurry."

"This teaches us more about the system," Dr. Alley said, referring to the new work.