There are around 60-80 volcanic eruptions per year; for a total of about 300 million tons of CO2; so all four together, even if they produce twice as much as an average eruption, would account for about only 3.5 million tons. (Human-produced CO2 is estimated at between 20 to 30 billion tons per year)
There are around 60-80 volcanic eruptions per year; for a total of about 300 million tons of CO2; so all four together, even if they produce twice as much as an average eruption, would account for about only 3.5 million tons. (Human-produced CO2 is estimated at between 20 to 30 billion tons per year)