Sunday, 22 March 2015

Mass Extinctions, and the link to atmospheric carbon

Five major mass extinction events are recorded in the rock record of the last 600 million years.
The biggest extinction was at the end of the Permian, around 252 million years ago.

It is called the End-Permian mass extinction.

Only about 8% of species survived to live on in the Triassic Period.

This photo shows geologists investigating tilted sedimentary rocks at Shangsi in South China.

Triassic rocks (at the top right) lie over the older Permian rocks.

Each mass extinction in the rocks matches with a change in the chemistry of the rocks called a 'carbon excursion'.

Some of the carbon excursions are 'negative CEs' and some are 'positive CEs'.

Negative CEs indicate that lots of gaseous carbon compounds escaped into the air, causing warming.

These are sometimes called hyperthermal events.

An example of a Negative CE is 

Ecosystems recovered from the PETM ..... it 'only' took 100,000 years.

In the PETM link above, see Section 9 ..Conclusions... last sentence.....

"the PETM is a natural analogue for increases in atmospheric COdue to fossil fuel burning over the next century, and implies a relatively high climate sensitivity."

Positive CEs involve the opposite..... the Earth absorbs the gases and cooling follows.

Examples of positive CEs include 

The 'Snowball Earth' events.

The Earth Systems simply react to the chemistry.

The changes were caused by natural processes in the past.
This time human activity is involved.

Currently CO2 is rising at 20 ppm per decade.

Nothing like this has happened in the time of Homo sapiens.

Uncontrolled addition of CO2 is dangerous and will have serious consequences.

Photographs of ice cores being collected by drilling

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