Big volcanic eruptions cool the atmosphere for some years due to the aerosols (sulphates) thrown up above the tropopause roughly 10 kilometers up in the sky. The greenhouse gases from big eruptions may cause changes in the weather for 2-3 years. This is not enough to have any significant impact on climate – the average weather over 30 years
There is very little carbon present in magma; the molten rocks in a volcano. (Look up magma in any encyclopedia!) This is in case a small amount compared to the contributions from human combustion of oil over a year. You should remember that greenhouse gases are invisible. When you see a volcanic eruption, you see particles – aerosols – not greenhouse gases. The relatively small amounts of carbon dioxide and water coming from the exsolution processes in volcanic eruptions are as a rule easily taken care of by natural buffers (vegetation, corals, oceans) over a couple of years unless we talk about a supervolcano. Volcanic eruptions might contribute at the most 1% of the greenhouse gases in the atmosphere.
“It would take a huge addition of volcanoes to the subaerial landscape — the equivalent of an extra 11,200 Kīlauea volcanoes — to scale up the global volcanic CO2 emission rate to the anthropogenic CO2 emission rate. Similarly, scaling up the volcanic rate to the current anthropogenic rate by adding more submarine volcanoes would require an addition of about 360 more mid-ocean ridge systems to the sea floor, based on mid-ocean ridge CO2 estimates of Marty and Tolstikhin.
There continue to be efforts to reduce uncertainties and improve estimates of present-day global volcanic CO2 emissions, but there is little doubt among volcanic gas scientists that the anthropogenic CO2 emissions dwarf global volcanic CO2 emissions.” Reality drop
- Volcanic vs. Human-Caused CO2 Emissions – Updated Graphic
- A drop in volcanic activity caused warming
- What do volcanic eruptions mean for the climate?
- Why natural cycles only play small role in rate of global warming
- Humans Release 40 to 100x More CO2 Than Volcanoes, Major Study Reveals