What most people do not understand is that we are in a rare icehouse phase. The question is the danger to us of triggering a transition to a greenhouse.
'A "greenhouse Earth" is a period during which no continental glaciers exist anywhere on the planet. Additionally, the levels of carbon dioxide and other greenhouse gases (such as water vapor and methane) are high... Earth has been in a greenhouse state for about 85% of its history.
'Earth is now in an icehouse state, and ice sheets are present in both poles simultaneously... Earth's current icehouse state is known as the Quaternary Ice Age and began approximately 2.58 million years ago... Earth is expected to continue to transition between glacial and interglacial periods until the cessation of the Quaternary Ice Age and will then enter another greenhouse state.'
