Understanding Earth's Deep Past: Lessons for Our Climate Future

摘要

"By the end of this century, without a reduction in emissions, atmospheric CO_2 is projected to increase to levels that Earth has not experienced for more than 30 million years." Throughout its long history, Earth has had two fundamentally different climate states: a cool "icehouse" of waxing and waning continental-based ice sheets at high latitudes, and a "greenhouse" state characterized by much warmer temperatures globally and only small-or no-ice sheets. Earth has been in an icehouse state throughout the time that humans evolved and for the previous 30 million years, but it has been in the warmer greenhouse state for most of the past 600 million years of geological time.