As we all know, a great deal of the carbon dioxide in out atmosphere is due to anthropogenic sources. There are natural processes and cycles, however, that release CO2 from the lithosphere (Earth’s crust) back into the atmosphere.
Natural CO2 release mechanisms include decomposition, respiration, and outgassing from volcanoes. This outgassing includes activity like eruptions (explosive and quiescent), geothermal vent release, and the nature of chemosynthetic environments.
The emission of CO2 through volcanic sources is essential to the carbon cycle. Although the total amount of carbon dioxide released from volcanoes is minor, it still makes a difference.
During an explosive volcanic eruption, gasses and matter are expelled. This matter consists of magma, ash, and dust which is at a temperature of about 800 degrees Celsius. Despite the fact that heat is released from this matter, it also acts to block the suns UV rays. Both of these processes alter the temperature of the Earth.
The quiescent gasses that are constantly emitted are composed of carbon dioxide, sulfur dioxide, nitrous oxides, and water vapor. These all aid in the increase of average global temp.
Here’s a little more info having to do with anthropogenic vs.volcanic emissions of carbon dioxide. Take a peek and look at the quantitative measures and observations relating to this matter.