It’s no secret that volcanic eruptions can cool the planet by spewing ash and droplets of sulfuric acid into the atmosphere that obscure the sun. Now researchers at Germany’s GEOMAR Helmholtz Centre for Ocean Research Kiel and Harvard University have found evidence that suggest the reverse could also be true. The researchers have discovered a strong historical link between global temperature increases and increases in volcanic activity.

Using observations of ash layers in cores taken from the seafloor around the Pacific region, the researchers reconstructed the history of volcanic eruptions for the past one million years. When they compared this data with the climate history, they found that periods of fast, global temperature increases and associated ice melting were followed with periods of high volcanic activity.

Ash layers in cores from the Pacific seafloor (Photo: S. Kutterolf, GEOMAR)

Using geological computer models, the researchers have come up with a possible explanation for the link.

"In times of global warming, the glaciers are melting on the continents relatively quickly,” says Dr. Marion Jegen, a geophysicist from GEOMAR. “At the same time the sea level rises. The weight on the continents decreases, while the weight on the oceanic tectonic plates increases. Thus, the stress changes within in the earth to open more routes for ascending magma."

Because the rate of global cooling at the end of warm phases is much slower compared to the rate of warming at the beginning of such phases, there are less dramatic stress changes and less volcanic activity during these times.

"If you follow the natural climate cycles, we are currently at the end of a really warm phase,” says Dr. Steffen Kutterolf, the lead author of the study. “Therefore, things are volcanically quieter now.”

Kutterolf adds that since the impact from man-made warming is still unclear, the next step will be to investigate shorter-term historical variations in an effort to understand the implications for the present day.

The results of the team’s study are published in the journal Geology.

Source: GEOMAR