2. Glacial polish (Ice age in the greenhouse?)

Climate has always changed
Geologists can look back a long way into the past using rock deposits and fossils. We know today that climate change is nothing new. Over many millions of years Earth has experienced both extremely cold and extremely hot phases.

Snowball Earth
Very old rocks indicate glaciers and ground freezing near the equator. Scientists believe that at the time the earth was mostly if not completely frozen over. From space earth might have looked like a snowball. But at that time, more than 600 million years ago, in the Precambrian period, no animals lived on the frozen continents.

Hot earth
About 50 million years ago (in the early Eocene), there was a hot period. The global average temperature was about 13 °C higher than today (with CO2 at 1400 ppm). Even in the Antarctic there was no ice, and the sea level was about 70 meters (230 feet) higher than it is today. The cause was probably a strong increase of greenhouse gases within a few millennia. Mass extinctions happened in many oceans while many regions on the continents experienced droughts.

And today?
Man-made greenhouse gasses are emitted about ten times faster than those at the beginning of the Eocene. Can mankind stop the trend in time before the current climate system collapses and irreversible, natural, self-reinforcing processes lead to a new hot season?

Literature and Links:

Literature and Links:

The panel for download as pdf (612.5 KB)