Climate Central: Climate scientists don’t just rely on computer models and contemporary observations to understand the intimate relationship between CO2 in the atmosphere and environmental conditions on Earth. They also look to the ancient past — and two reports in recent days have made it clear how intimate that relationship is. One chronicles an episode 2.4 billion years in the past, when the entire planet was covered in a layer of ice hundreds of feet thick, oceans and all, while global average temperatures hovered around 40° F below zero.

A massive infusion of heat-trapping CO2 from powerful volcanoes — more CO2 than we’re likely to emit in many hundreds of years, to be sure — saved the planet from this so-called Snowball Earth environment. The second report covers an event that happened about 250 million years ago, and this time the effects weren’t so benign. Another set of gigantic eruptions poured enough CO2 into the air not only to warm the planet drastically, but also to acidify the oceans so profoundly that some 90 percent of all ocean species died off, followed by two-thirds of land species. It’s the worst mass extinction, as far as we know, in history.

These monumental episodes of climate change, both linked intimately to levels of CO2 in the atmosphere, are a testament to the dramatic effects this greenhouse gas has on the entire planet. So it’s no surprise that the smaller amounts we’re emitting could have a significant effect as well. [Continue reading…]