DENVER — A trove of ancient bones from gigantic animals discovered in the Colorado mountains is providing scientists with a fascinating look at what happened about 120,000 years ago when the Earth got as warm as it is today.
Evidence left behind by mastodons, mammoths, giant sloths, and huge bison — along with insects, plants, pollen, and other animals — offers a glimpse at how ancient animal adapted to climate change.
Among their findings: The warmer weather allowed forests to reach about 2,500 feet farther up the mountainside than today’s tree line, which is about 11,500 feet above sea level at the Snowmass site. Forests also may have been denser, and smaller trees and grasslands might have been more widespread amid drier conditions.
A team of 47 scientists has been studying material unearthed four years ago near Snowmass, a town just outside Aspen, when a bulldozer was enlarging a reservoir. The researchers published their first big batch of data in the journal Quaternary Research in November.
‘‘The site is spectacular because it has a single continuous pile of sediment from the most recent interglacial period,’’ about 120,000 years ago, when conditions were similar to the present, said Ian Miller, chairman of the Earth Sciences Department at the Denver Museum of Nature and Science. He is codirector of the museum’s Snowmastodon Project, which is sifting through the material.
‘‘It’s a beautiful record of the last time it was as warm or warmer than it is today,’’ he said.
The information gives scientists solid data to check their climate models against.
It also means that figuring out the impacts of human-produced greenhouse gases combined with natural changes might be more complicated than previously thought.
The Colorado site can point to clues about how life adapts to climate change but doesn’t answer the question, according to a climate scientist not working on the Snowmass site.
The reservoir where the bones were found was originally a natural lake and sits on a ridge approximately 9,000 feet above sea level. The sediment and bones provided a record of about 85,000 years, from 140,000 years ago to 55,000 years ago.