The Earth's current warming is looking similar to what took place 55 million years ago, writes David Bond. And if it works out that way, the news is good: we may avoid a mass extinction. On the other hand, the poles will melt away completely, and it will take hundreds of thousands of years for Earth to get back to 'normal'. It is often said that humans have caused the Earth to warm at an unprecedented rate. However researchers have discovered another period, some 55m years ago, when massive volcanic eruptions pumped so much carbon into the atmosphere that the planet warmed at what geologists would think of as breakneck speed. The good news is that most plants and animals survived the warm spell. The planet has experienced several mass extinctions - and this wasn't one of them. But there's a catch: even after carbon levels returned to their previous levels, the climate took 200,000 years to return to normal.
The Earth's current warming is looking similar to what took place 55 million years ago, writes David Bond. And if it works out that way, the news is good: we may avoid a mass extinction. On the other hand, the poles will melt away completely, and it will take hundreds of thousands of years for Earth to get back to 'normal'.
It is often said that humans have caused the Earth to warm at an unprecedented rate.
However researchers have discovered another period, some 55m years ago, when massive volcanic eruptions pumped so much carbon into the atmosphere that the planet warmed at what geologists would think of as breakneck speed.
The good news is that most plants and animals survived the warm spell. The planet has experienced several mass extinctions - and this wasn't one of them.
But there's a catch: even after carbon levels returned to their previous levels, the climate took 200,000 years to return to normal.
Geologists have a name for this earlier period of sudden warming: the Palaeocene-Eocene Thermal Maximum. The PETM, as we'll call it, occurred 55.5-55.3 million years ago.
According to new research published in the journal Nature Geoscience it involved global warming of between 5 and 8°C over a period of 200,000 years.
The massive carbon injections responsible for the PETM probably originated in volcanic eruptions in the North Atlantic and the burning of organic-rich rocks through which lava passed, which further triggered the melting of frozen methane stored at the bottom of the deepest oceans.
Lessons from the PETM
There are obvious analogies between the PETM and the present-day situation, even despite the lack of fossil-fuel burning humans 55m years ago.
The study shows the PETM was caused by annual carbon emissions of at least 900 million tons (900 MT) over the 200,000 years. That is ten times less than the 9500 MT carbon humans are releasing into the atmosphere every year. Surely cause for concern?
However, it is a little misleading to suggest emissions of just 10% of current levels resulted in warming of 5°C or more. It is possible to zoom out too far, even when assessing climate change.
Considering that CO2 only sticks around in the atmosphere for 1,000 years at most, to achieve as much as 8°C warming the bulk of PETM carbon must have been delivered to the atmosphere in a very short time, during which the long-term average was greatly exceeded.
Continue reading at ENN affiliate, The Ecologist.
Melting Earth image via Shutterstock.
