In the distant past, about 56 million years ago, the earth experienced global warming on a much larger scale than what climate scientists are predicting we will see in the worst case due to current natural warming and additional warming due to man-made carbon dioxide emissions. The event, known as the Pliocene/Eocene Thermal Maximum (or PETM), is described this short PBS documentary.
Why is this important? Because it shows what happens when there is a massive release of CO2 and the earth’s temperature warms by 8C (or 15F). On the negative side, ocean’s became more acidic and vast numbers of marine animals died off, including coral. On the positive, tropical rain forests spread across much of the globe. The PETM provides a model of what the earth will be like if we allow the atmosphere’s CO2 concentration to increase too much
One of the major differences between the warming that led to the PETM and the current warming we are experiencing and contributing to is the rate at which the concentration of CO2 in the atmosphere is increasing. Though in geological terms, CO2 concentration increased very quickly before the PETM occurred, we are currently increasing it much more rapidly. We have no idea what problems this high rate of change will cause. This is the true danger of man made climate change.
