A discovery showing that Montana was much warmer 6,000 years ago, is evidence of dramatic warming.

“The forest, which endured for centuries before cooling temperatures forced it to retreat downslope, was sealed under ice approximately 5,500 years ago due to a shift in summer solar radiation and subsequent volcanic cooling.

“This is pretty dramatic evidence of ecosystem change due to temperature warming. It’s an amazing story of how dynamic these systems are,” said David McWethy, one of the study’s authors and an associate professor in Michigan State University (MSU’s) Department of Earth Sciences.”

Fossilized frozen forest discovered in the US under thawing tundra – Earth.com