'Global cooling as significant as global warming'

A "cold snap" 116 million years ago triggered a marine ecosystem crisis similar to those witnessed as a result of global warming, a new study claims.
The international study involving experts from the universities of Newcastle, UK, Cologne, Frankfurt and GEOMAR-Kiel, confirms the link between global cooling and a crash in the marine ecosystem during the mid-Cretaceous greenhouse period.
It also quantifies for the first time the amplitude and duration of the temperature change. Analysing the geochemistry and micropaleontology of a marine sediment core taken from the North Atlantic Ocean, the team showed that global temperature drop of up to 5 degrees Celsius resulted in a major shift in the global carbon cycle over a period of 2.5 million years.

Occurring during a time of high tectonic activity that drove the breaking up of the super-continent Pangaea, the research explains how the opening and widening of new ocean basins around Africa, South America and Europe created additional space where large amounts of atmospheric CO2 was fixed by photosynthetic organisms like marine algae.
The dead organisms were then buried in the sediments on the sea bed, producing organic, carbon rich shale in these new basins, locking away the carbon that was previously in the atmosphere.
The result of this massive carbon fixing mechanism was a drop in the levels of atmospheric CO2, reducing the greenhouse effect and lowering global temperature.

This period of global cooling came to an end after about 2 million years following the onset of a period of intense local volcanic activity in the Indian Ocean.

Producing huge volumes of volcanic gas, carbon that had been removed from the atmosphere when it was locked away in the shale was replaced with CO2 from the Earth's interior, re-instating a greenhouse effect which led to warmer climate and an end to the "cold snap".
Researchers say this study highlights how global climate is intrinsically linked to processes taking place in the Earth's interior at million year time scales and that these processes can modify ecospace for marine life, driving evolution.

The study shows that if global temperatures swing the other way by a similar amount, the result can be just as severe, at least for marine life.
The study was published in Nature Geoscience.