Ancient climate change was driven by volcanoes, researchers say

Ancient climate change that saw surface temperatures soar by 5C around 56 million years ago was driven by volcanoes, a study has suggested.

Researchers who investigated sediment preserved on the Danish island of Fur believe that huge amounts of greenhouse gases released by volcanoes may have raised temperatures.

Previously, scientists believed that temperatures in the Paleocene–Eocene Thermal Maximum (PETM) may have risen due to a change in the tilt of Earth's axis, resulting in an uplift of land that led to the weathering of undersea rocks.

Increased carbon emissions would make sense, due to a spike in lighter carbon recorded in the shells of fossil micro-organisms – foraminifera – living in the oceans at the time.

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The volcanoes in question are in the huge North Atlantic Igneous Province (NAIP) located between Greenland, north of the UK and west of Norway.

The total volume of magma is thought to have been up to 239,912 cubic miles, equating to a carbon reservoir of 35,000 gigatons.

Researchers led by Dr. Morgan Jones, from the University of Oslo, turned to the sediment record preserved on the island of Fur, where a complete section of sediment from the era is visible, having been uplifted from the seafloor over millennia.

Here, hundreds of ash layers can be found, which the scientists analysed.

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Minerals in the deposits suggest volcanic activity increased in the lead-up to the warming period, before declining rapidly.

Jones suggested a distinct change in the activity of the NAIP from effusive (outpouring of lava onto the ground) to explosive (including ash clouds and volcanic bomb) over this period.

High levels of methane would have contributed significantly to global warming as it is a powerful greenhouse gas, 28 times more potent than carbon dioxide at trapping heat over a 100-year period.

The researchers believe that after the warming period, greenhouse gases from the atmosphere were absorbed into rocks, lowering the temperature quickly.

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