The volcano/CO2 story flip-flops depending on what the agenda for the day is. Some days it is convenient to blame past climate change on volcanic CO2.
Multiple phases of carbon cycle disturbance from large igneous province formation at the Triassic-Jurassic transition
M. Ruhl and W.M. Kurschner, Palaeoecology, Laboratory of Palaeobotany and Palynology, Institute of Environmental Biology, Faculty of Science, Utrecht University, Budapestlaan 4, NL-3584 CD Utrecht, Netherlands; doi: 10.1130/G31680.1.
The end-Triassic mass extinction event (~200 million years ago) is one of the Big Five mass extinction events in earth history. It is marked by global extinction of up to 50% of all species living in the oceans and by large changes in ecosystems on the continents. The cause for the extinction event is related to strongly intensified volcanic activity and deposition of the largest basalt deposit on Earth, the Central Atlantic Magmatic Province. Recent studies show that the end-Triassic mass extinction event directly coincided with the onset of this volcanic period that lasted for ~600,000 years. The release of massive amounts of carbon dioxide from volcanism triggered a strong change in the global carbon cycle and likely had a strong impact on global climate. M. Ruhl and W.M. Kurschner of Utrecht University show, however, that a strong increase in atmospheric carbon dioxide of up to 1000 parts per million (today’s values are ~350 parts per million) and a strong change in the global carbon cycle already occurred ~100,000 years before the onset of intense volcanism. This suggests that large amounts of carbon dioxide were already released by the thermal heating of organic-rich sediments by intrusion of magma bodies from the mantle on their way to Earth’s surface.
On other days, they want to prove that volcanoes aren’t major contributors of CO2.
The burning of fossil fuels and changes in land use results in the emission into the atmosphere of approximately 30 billion tonnes of carbon dioxide per year worldwide, according to the EIA. The fossil fuels emissions numbers are about 100 times bigger than even the maximum estimated volcanic CO2 fluxes. Our understanding of volcanic discharges would have to be shown to be very mistaken before volcanic CO2 discharges could be considered anything but a bit player in contributing to the recent changes observed in the concentration of CO2 in the Earth’s atmosphere.