Some researches exhibit that volcano can be a major source of CO2 increasing in the atmosphere. A study finished in 1997 showed the composition of volcanic gases from Galeras Volcano in Colombia. Basic solution and an equipment called Japanese box were used to collect and analyze the acidic gases in the air from the volcano, and titration was used to test CO2, and the data of gas composition from 1989-1992 was recorded (Alfaro & Zapata, 1997). According to the result, the amount of CO2 collected from the volcanic gas changed every year, but it always overweighed other gases such as HCl and SO2. The researchers also pointed that Galeras volcano was active and had several times of eruption in last century (Alfaro & Zapata, 1997), which shows that it can release a large amount of CO2 to the atmosphere.
Another research that was done recently studied Katla as a volcano that is an important source of volcanic CO2 emission on the earth and is active recently even if it has not erupted for a century. The concentration of CO2 in different areas around Katla was observed, stimulated and modelled using aircraft, and the emission rate was calculated based on the result of the observation and modelling. According to the calculation, the CO2 emission rate of Katla was about 12–24 kt per day (Ilyinskaya et al., 2018). Researchers also state that Katla is the third major source of volcanic CO2 emission, and the volcano is unrest due to the movement of magma (Ilyinskaya et al., 2018).
On the other hand, there are also evidences demonstrate that CO2 in the atmosphere increases due to the anthropogenic emissions. A research in 1984 calculated CO2 emission rate of fossil fuels combustion from 1950 to 1982. It showed that the emission rate maintains an upward trend, even if it dropped a little bit from 1979 (5, 373×106 t) to 1982 (5, 102×106 t) (Marland & Rotty, 1984). In 2002, the
Even though there are a number of evidences support both side, it is still more convincible that major reason for the increasing of CO2 is anthropogenic emissions. According to recent studies, the global emission rate of volcanic CO2 was about 637mt per year (Burton et al., 2013), and the global anthropogenic CO2 emission had reached 32,000mt per year approximately (Friedlingstein et al. 2010), which outweigh the global volcanic CO2 rate a lot.