"Earth is more commonly placed in a greenhouse state throughout the
epochs, and the Earth has been in this state for approximately 80% of
the past 500 million years, which makes understanding the direct causes
"During an icehouse Earth, greenhouse gases tend to be less abundant, and
temperatures tend to be cooler globally. The Earth is currently in an
icehouse stage, as ice sheets are present on both poles and glacial periods have occurred at regular intervals over the past million years."