"Earth had a climate long before we showed up and started noticing it, and it's influenced by a whole series of cycles that have been churning along for hundreds of millions of years. In most cases those cycles will continue long after we're gone. A look at the history of climate change on Earth can give us some much needed perspective on our current climate dilemma because the surprising truth is, what we're experiencing now is different than anything this planet has encountered before....."
A History of Earth's Climate (11 min.)
Demonstration of Greenhouse Effect: In Earth's early history, the sun was 30% dimmer than it is today, which is to say that the sun was only 70% as bright then as it is now. But, because the atmosphere was laden with methane, a potent greenhouse gas, the temperature on Earth was very hot, nonetheless. Much later, the methane and carbon dioxide were so sufficiently removed from the biosphere by Cyanobacteria that the Earth became completely frozen over. After that, an oxygen CO2 balance became established and then roughly maintained -- until we artificially unsequestered massive amounts of CO2 in a very short time. Eventually, the balance will be reestablished; but, not before the aftermath of the 'amplified greenhouse effect' aka 'global warming' reeks havoc on our biosphere.
Hottest and Coldest Earth Has Ever Been: