Over the last few years there have been a number of studies showing both short term and long term climate impacts linked to volcanic activity. While there is strong scientific consensus that humans are responsible for excessive greenhouse gasses, which is causing climate change it is becoming increasingly clear that volcanic activity contributing as well. However, in the case of volcanos, arriving at a consensus may take awhile.

The most recent study, published in Geophysical Research Letters, examines the role of volcanic activity in deeply submerged mid-ocean ranges. Specifically, the report looks at mid-ocean ridges where molten rock from the Earth’s interior creates new planetary crust.

This activity coincides with natural 100,000 year changes in Earth’s orbit around the sun, which correspond to changes in climate.

“Generally, mid-ocean ridges are thought of as this tiny, not very significant contributor to the carbon cycle and that is true, but that’s because they are thought of as a steady-state process. But, if they go through periods of significantly enhanced volcanism and significantly suppressed volcanism, then they may be more important than we thought,” said Maya Tolstoy in a statement.

Tolstoy is an associate professor at Lamont-Doherty Earth Observatory at Columbia University in New York and sole author of the new study.

In her research Tolstoy studied 10 present-day eruptions at mid-ocean ridges. She also examined traces of ancient volcanic activity from a mid-ocean ridge.

Tolstoy found that when gravitational forces from the moon and sun were low, and carbon dioxide in the atmosphere is high there were more eruptions. The number of eruptions went down when the Earth’s orbit was more circular and carbon dioxide was low. Additionally, she found a correlation between sea level and volcanism, with activity declining as sea levels rose.

The study does not put a value on the amount of Co2 being produced by undersea volcanos. However it does add another piece to the overall climate puzzle, possibly creating the need to modify current models.

Tolstoy’s research seems somewhat at odds with a 2012 study in the journal Geology. In that study researchers found that rising sea levels, not lowering levels, increased volcanic activity.

“In times of global warming, the glaciers are melting on the continents relatively quickly. 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,” said Dr. Marion Jegen, a geophysicist from GEOMAR Helmholtz Centre for Ocean Research Kiel at the time.

Another study, published in Nature Geosciences in February 2014 demonstrated that volcanic activity could be behind the global warming ‘hiatus’. The researchers found that, although volcanos release large amounts of Co2, compounding climate change in the long term, they also release sulfur dioxide.

The sulfur dioxide, the substance behind acid rain, can combine with moisture in the atmosphere and reflect heat back into space. This can produce a short term cooling effect.

Additionally there is some evidence that lava, as it cools into rock, absorbs Co2 from the atmosphere. Finally, according to recent estimates, about one-quarter of the Co2 produced by human activity is absorbed by the oceans.

Tolstoy, in her study, couldn’t estimate the amount of Co2 being released by undersea volcanos. If the Co2 is released underwater, it is likely that a larger than normal amount of it would be absorbed but its possible that by absorbing the Co2 from undersea volcanos, the ability of oceans to absorb airborne C02 could be impacted.

Overall, we are left with a confusing picture. There are conflicting studies showing volcanic activity increasing or decreasing with climate change. There is evidence that volcanos contribute to global warming in the long term, but may cause cooling in the short term and evidence that the lava from those volcanos could help absorb atmospheric Co2.

While there is a strong consensus that man made Co2 is the cause of current climate change it is also increasingly clear that volcanos play a role and that that role should be accounted for in climate models. However a consensus on the overall, very complicated, role of volcanism in climate change does not seem to be coming soon.

“We know that we can’t study these systems in isolation, that all of these different parts of our planet are linked. This study is just showing that deep-seafloor volcanism, which is sort of out of sight, out of mind, may have a long-term feedback into our whole climate system. If we are going to protect Earth we have to understand how the planet functions as a whole,” said Tolstoy.