The hottest warm period in the past million years is believed to have occurred about 400,000 years ago. During this time, the Northern Hemisphere had less ice than today, and sea levels were about 10 meters higher. Surprisingly, solar radiation, a key driver of warm periods, was weak during this time, and greenhouse gas levels were lower than today. This puzzling period, known as the MIS 11c paradox, has long baffled scientists.
