How much CO2 did major historical eruptions like Mount Pinatubo and Tambora emit compared to annual human emissions?
Executive summary
Explosive eruptions such as Mount Pinatubo and historic giants like Tambora released tens to perhaps hundreds of millions of tonnes of CO2 in single events — large for a moment but tiny compared with modern human emissions measured in tens of billions of tonnes per year [1] [2] [3]. Aggregated global volcanic degassing each year is estimated at roughly 0.13–0.44 gigatonnes (130–440 million tonnes) of CO2, which is a small fraction — generally reported as less than 1% — of contemporary anthropogenic CO2 released annually [4] [5] [6].
1. Mount Pinatubo in numbers: a headline eruption, a modest CO2 pulse
The best-cited measurements for Pinatubo put the erupted CO2 at roughly 42 million tonnes for the major 1991 paroxysm, and time‑averaged emission-rate analyses imply the event vented CO2 at rates comparable to human global emissions only for a few hours (Pinatubo’s instantaneous rate was on the order of 0.006 gigatonnes per hour, giving a multi‑hour pulse) [1] [7] [8]. By contrast, global anthropogenic CO2 in 1991 was about 23 billion tonnes, so the single Pinatubo blast was roughly three orders of magnitude smaller than that year’s human output [1].
2. Tambora and the limits of the record: huge climate impacts, uncertain CO2 totals
Tambora’s 1815 eruption is widely documented for its prodigious aerosol load and climatic “year without a summer,” with estimates of erupted volume near 50 km3 and aerosol burdens several times Pinatubo’s, but direct, precise quantification of Tambora’s CO2 release is not provided in the sources reviewed; its climatic legacy owes more to sulfur aerosols than to long‑lived CO2 spikes [8]. The reporting emphasizes that very large eruptions can inject vast aerosol masses that cool the planet for years, and while Tambora likely released far more material than Pinatubo, existing summaries here do not offer a reliable tonnes‑of‑CO2 figure to stake a numeric comparison to modern human annual emissions [8].
3. Volcanoes per year vs humans per year: the aggregated picture
Modern scientific syntheses put global volcanic CO2 emissions (subaerial plus submarine) in the range of ~0.13–0.44 gigatonnes per year (130–440 million tonnes), and multiple agencies summarize that volcanoes emit less than about 1% of current human CO2 emissions, meaning anthropogenic emissions — on the order of roughly 24–35 gigatonnes CO2 per year in recent decades — dwarf volcanic sources by factors of dozens to a few hundred depending on the specific estimates used [4] [5] [2] [3]. NOAA and related analyses highlight that while brief eruption‑rate peaks can match human hourly rates, they are fleeting and rare, so they do not challenge the persistent, accumulating legacy of fossil‑fuel emissions [9] [2].
4. Why the numerical gap matters for climate interpretation
The scientific literature and agencies warn that confusing short‑term, high‑rate volcanic emissions with sustained fluxes misleads public understanding: an eruption that emits as much CO2 as humanity does in a few hours still leaves humans responsible for a ceaseless stream of tens of gigatonnes per year that accumulates in the atmosphere [5] [2] [6]. Moreover, large explosive eruptions often cool the surface because of sulfur aerosols — the dominant immediate climatic effect — so even spectacular blasts historically produced short‑term cooling rather than stepwise upward jumps in global temperature attributable to CO2 alone [8] [10].
5. Uncertainties, disagreements, and the takeaways
Estimates of both volcanic and anthropogenic emissions carry uncertainty and methodological differences — global volcanic CO2 ranges in the literature span roughly 0.13–0.44 Gt/yr and anthropogenic annual totals depend on the year and inventory (roughly 23–35 Gt/yr in sources cited), which produces a ratio that experts express variously as “at least ~60 times” to “more than 90 times” greater human emissions than volcanic ones [4] [9] [7]. Where the sources do not give a precise CO2 mass for Tambora, it is responsible for outsized aerosol-driven climate effects rather than a demonstrably comparable CO2 burden to modern human emissions [8]. The clear, cross‑checked conclusion in the reporting is uncompromising: occasional eruptions can produce impressive short‑term CO2 rates, but they do not come close to matching humanity’s sustained, cumulative CO2 emissions on an annual or multi‑decadal basis [5] [2] [6].