New research finds that ancient carbon in rocks releases as much carbon dioxide as the world's volcanoes https://perma.cc/S4WT-RGB5

A new study led by the University of Oxford has overturned the view that natural rock weathering acts as a CO2 sink, indicating instead that this can also act as a large CO2 source, rivalling that of volcanoes. The results, published today in the journal Nature, have important implications for modelling climate change scenarios.

Professor Robert Hilton (Department of Earth Sciences, University of Oxford), who leads the ROC-CO2 research project that funded the study, said: “This is about 100 times less than present day human CO2 emissions by burning fossil fuels, but it is similar to how much CO2 is released by volcanoes around the world, meaning it is a key player in Earth’s natural carbon cycle”.

A new study finds volcanic activity played a direct role in triggering extreme climate change at the end of the Triassic period 201 million year ago, wiping out almost half of all existing species. The amount of carbon dioxide released into the atmosphere from these volcanic eruptions is comparable to the amount of CO2 expected to be produced by all human activity in the 21st century https://perma.cc/VR49-5KBU

Effect of volcanic eruptions significantly underestimated in climate projections https://perma.cc/FAS7-P7D7

While this effect is far from enough to offset the effects of global temperature rise caused by human activity, the researchers, led by the University of Cambridge, say that small-magnitude eruptions are responsible for as much as half of all the sulphur gases emitted into the upper atmosphere by volcanoes.

The results, reported in the journal Geophysical Research Letters, suggest that improving the representation of volcanic eruptions of all magnitudes will in turn make climate projections more robust.

However, these large eruptions only happen a handful of times per century – most small-magnitude eruptions happen every year or two.

... not compare with human CO2 ..

The fluctuations in plume CO2/SO2 ratios at Stromboli reflect temporal changes in the relative gas contributions from the deep (CO2-rich) and shallow (CO2-poor and SO2-rich) magma storage zones (53). Hence, a high CO2/SO2 ratio does not necessarily imply an elevated deep gas flux and, instead, can also derive from a reduced level of shallow magma degassing. For example, we propose that a reduced SO2 contribution from shallow conduit magma is likely to have caused the ~4-month-long (September to December 2019) period of high CO2/SO2 ratios following the 2019 unrest, as supported by concurrent stable, low SO2 concentrations (Fig. 2A) and declining SO2 fluxes (Fig. 4A).

To unequivocally identify periods associated with heightened deep CO2 release, we rely on our CO2 flux record (Figs. 4B and 5). This time series highlights, unambiguously, that a surge of deep CO2 gas is associated with Stromboli’s unrest during summer 2019, with daily CO2 fluxes peaking at a factor of ~4 above typical background values (<1000 tons/day) before both blasts. Our results provide compelling evidence that volcanic CO2 flux is an effective tracer of deep degassing, thus supporting previous work at Etna (21, 32, 54), Villarrica (27), Turrialba (28), and Poás (29), where elevated fluxes of deep-derived volatiles have been shown to precede paroxysmal eruptions of basaltic magma.

We note that the 2014 effusive unrest—the only post-2000 event not associated with a paroxysmal explosion—is consistently charac- terized by the lowest excess CO2 degassing budget (Fig. 8). Therefore, it appears that in 2014, the effusion had less of an impact on the deep plumbing system than in 2007 and 2019. It is possible that Stromboli’s deep reservoir experienced decompression in 2014, too, but the volume of CO2 gas involved was sufficiently low to preclude the unrest culminating into a paroxysm. Lower effusion-driven magma decompression rates in 2014 (8.4 Pa/s), relative to 2007 (29.3 Pa/s), may have been responsible for the reduced levels of CO2 degassing.