Check out this answer from Consensus:
While volcanoes are a natural source of CO2, their annual emissions are dwarfed by those from human activities. The scientific consensus is clear: human activities are the dominant source of CO2 emissions, contributing significantly more to atmospheric CO2 levels than volcanic activity. This understanding is crucial for informing climate policy and mitigation efforts aimed at reducing anthropogenic CO2 emissions.
The question of whether volcanoes release more carbon dioxide (CO2) annually than human activities is a topic of significant interest, particularly in the context of climate change. Understanding the contributions of both natural and anthropogenic sources of CO2 is crucial for developing effective strategies to mitigate global warming. This article examines the current scientific understanding of CO2 emissions from volcanoes compared to those from human activities, drawing on recent research findings.
Volcanic CO2 Emissions
Volcanoes are a natural source of CO2, releasing this greenhouse gas through both eruptive and non-eruptive processes. Recent studies have made significant progress in quantifying these emissions, although challenges remain.
Subaerial Volcanism
Subaerial volcanism, which includes emissions from active crater fumaroles, plumes, and diffuse degassing via soils, volcanic lakes, and aquifers, is a major focus of research. Current estimates suggest that persistent degassing from active volcanoes releases between 53 and 88 teragrams (Tg) of CO2 per year, with the most actively degassing volcanoes contributing approximately 36.4 ± 2.4 Tg CO2 annually1. Additionally, diffuse degassing could contribute as much as 83 to 93 Tg CO2 per year, making it a significant but less well-characterized source1.
Volcanic Lakes
Volcanic lakes also play a role in global CO2 emissions. Research indicates that these lakes emit around 117 ± 19 megatons (Mt) of CO2 annually, with deep-seated CO2 accounting for 94 ± 17 Mt of this total4. This highlights the need for a comprehensive revision of global CO2 discharge estimates from subaerial volcanism.
Historical Eruptions
Historical data on volcanic eruptions provide additional context. For example, the period from 1800 to 1969 saw an average volcanic CO2 input of about 1.5 × 10^11 moles per year, which is significantly lower than current anthropogenic emissions2.
Anthropogenic CO2 Emissions
In contrast to volcanic emissions, human activities, particularly the burning of fossil fuels and deforestation, contribute vastly larger amounts of CO2 to the atmosphere. Current estimates place anthropogenic CO2 emissions at approximately 4 to 5 × 10^14 moles per year, far exceeding the contributions from volcanic sources2.
Comparative Analysis
The disparity between volcanic and anthropogenic CO2 emissions is stark. Research unequivocally shows that human activities emit far more CO2 annually than volcanoes. For instance, the total annual CO2 emissions from present-day volcanoes are comparable to the emissions from individual U.S. states like Florida, Michigan, and Ohio3. This comparison underscores the relatively modest contribution of volcanic CO2 to the global carbon budget.
Do volcanoes release more CO2 annually than humans?
Steven Sherwood has answered Extremely Unlikely
An expert from UNSW Sydney in Climatology, Atmospheric Science
CO2 emissions are measured from volcanoes and human activities; those from volcanoes are on average about 1% of those from us. Also, volcanoes are intermittent, so if they were emitting a lot we’d see spikes in the CO2 concentration over time. But, for example, Pinatubo (a very large eruption in 1991) had no discernible effect. Instead the observed increase in CO2 is steady, due to the steady nature of human activities (some bumps and a seasonal oscillation occur due to variations in uptake by plants). Finally, natural removal of CO2 is very slow (also 1% of human emissions), so if volcanoes were emitting so much as falsely claimed, we would have way more CO2 in the atmosphere by now than is actually the case.