Carbon dioxide emissions: Natural vs anthropogenic

Degassing of Earth is a continuous process… going on since 4 billion years. This process occurs  through volcanoes, both aerial and sub-aerial (below the oceans) and other rock formations buried  subsurface. It is difficult to quantify the amount of CO2 being ejected into the atmosphere from these  sources. All the published figures are estimates. Estimates made during nineties’ are of the order of 0.44  giga-tones (Gerlach, 1991; Allard,1992; Varekamp et al., 1992; Sano and Williams, 1996; Marty and  Tolstikhin, 1998). These references are given here only to support what is written here.  

Earth’s deep carbon cycle through deep time reveals balanced, long-term stability of atmospheric CO2,  punctuated by large disturbances, including immense, catastrophic releases of magma that occurred at  least five times in the past 500 million years. During these events, huge volumes of carbon were  outgassed (as pulses), leading to a warmer atmosphere, acidified oceans. and mass extinctions  

Take the case of the volcanic eruption over Indian subcontinent that occurred around 65 million years  ago. The Deccan volcanic province that occupies the entire Maharashtra State, represents thick lava  flows that were thrown on to the surface. 1.5 million km3 of lava was ejected to the surface along with  huge volume of gases including CO2 and S and water vapour. The CO2 emissions during the eruption of  these lavas were 5×1017 gm CO2 (500 million Gigagrams) (Chandrasekharam, 2003 Memoir Geological  Society of India). This volume of CO2 was ejected to the atmosphere over a period of 1 million years.  Similarly, a giant meteor impact, 66 million years ago, the Chicxulub bolide strike on Mexico’s Yucatan  peninsula, released between 425 to 1400 million Gigagrams CO2. Such catastrophic events released CO2 in a short period of time causing drastic changes in the surface temperature of the Earth resulting in mass  extinction of certain species on this planet. CO2 out-gassed to the atmosphere and oceans today from  volcanoes (submarine and sub aerial) and other magmatically active regions is estimated at 280 to 360  million tones (about 0.28 to 0.36 Gt) per year (360000 Gigagrams).  

These are all prehistoric eruptions. To get the feel of an eruption, we should remember the Mt. Pinatubu  eruption in Philippines in June 1991. Like all volcanic eruption this one was also predicted by the  scientists.  

The volcano exploded in a cataclysmic eruption that ejected more than 5 cubic kilometers of material.  

The ash cloud from this eruption rose 35 kilometers into the air. At lower altitudes, the ash was blown in  all directions by the intense cyclonic winds of a coincidentally occurring cyclone, and winds at higher altitudes blew the ash southwestward. A blanket of volcanic ash (sand- and silt-size grains of volcanic  minerals and glass) and larger pumice lapilli (frothy pebbles) blanketed the countryside. Fine ash fell as  far away as the Indian Ocean, and satellites tracked the ash cloud several times around the globe. The lava  flows retained the heat in the surrounding valleys till 1996. Nearly 20 million tons of sulfur dioxide was  injected into the stratosphere from Pinatubo’s 1991 eruptions, and dispersal of this gas cloud around the  world caused global temperatures to drop temporarily by about 0.5°C. Although there is no estimation on  the CO2 emissions, such kind of volcanic eruptions goes hand in hand with CO2 emissions. We may  assume the amount could be equivalent to SO2 emissions. I mentioned this because; it gives feel of a  catastrophic volcanic eruption followed by emissions. Similar is the case of the eruption of  Eyjafjallajokull volcano in Iceland in 2015. Such eruptions keep occurring and occurred ever since Earth  was formed!! CO2 emissions from the Earth is continuous even without volcanic eruption! 

Let us understand how Earth system responds to carbon dioxide emissions: These facts are based on  scientific investigations on the flora and fauna living in the oceans and on land. They are documented in  the IPCC (inter-governmental Panel for Climate Change) reports. 

It takes 50-200 years for 50% of this CO2 pulse to disappear. So those pulses of CO2 ejected by the  catastrophic volcanoes must have disappeared by now. Disappeared means it has not vanished but  consumed somewhere else… by the flora and fauna under the oceans and on the land and by natural  weathering process (for the formation of soils). The air temperature to respond to CO2 pulses takes about  120 to150 years. This means the mass extinction must have happened gradually after the major CO2 pulses from those catastrophic volcanic eruptions.  

Transportation and CO2 to deep oceans (Oceans are the major ink or CO2) takes about 100 to 200 years.  Sea-levels to respond to temperature change is about 10000 years and icecaps to respond to temperature  change is about 10000 years.  

On the socio-economic system……Change in Energy end use technology will take place in about 100  years and change energy supply technology takes about 10-50 years. To develop infrastructure to adapt to  the changing climate system will take 30-100 years and social norms and governance to adapt to the  changing climate system will take 30-100 years. However these are estimates. Scientists are deep into this  research to estimate to the nearest approximation the amount of CO2 emissions from the Earth’s interior.  The data on total amount of Carbon present in the Earth is available through estimation. The number is  huge……apparently it will be huge. Earth is a huge furnace and supports a variety of dynamic  processes……volcanic activity, earthquakes, hydrological cycle and of course life!! etc etc. 

I have talked about the natural emissions. Now let us understand a little about the anthropogenic  emissions.  

CO2 emissions from coal based power plants are the major source of anthropogenic emissions. What is  the amount of CO2 emitted when electricity is generated from such plants? When 1 unit of electricity (1  kWh) is generate by such plants, about 1 kg of CO2 is emitted. Any one can calculate this amount. The  number of active thermal power plants in the world is about 22882 generating 2045 Gigawatts of power  ( emitting 12  million Giga grams of CO2. If we include oil/gas/biomass/biofuels sources power plants the total  amount of anthropogenic CO2 amounts to 35 million Giga grams/year. This is far more than that  estimated emissions from the volcanoes.  

So, assuming that we shutoff all the thermal power plants today, it will take 50 years for the  equilibrium between to set in between the sea and the atmosphere…….sea being the major sink  for CO2. This means renewables should be able to supply 2045 Gigawatts (12 x 106 GWh) of  electricity (that too base-load power) to keep the GDP of any country at reasonable level. The  only energy source that can support and substitute coal based power is the Earth’s heat itself. The  world has a long way to go to achieve it. All these CoP meetings, discussions on 2Ds, 4Ds are all  mythical meetings by the elite group…… playing with the non-elite countries. These meetings  are making certain countries and selected companies rich. If the super powers have any  inclination to reduce CO2 emissions by substituting coal by Earth’s heat they should enact laws  to tap Earth’s heat on war-footing so that the world can achieve near zero emissions in another  decade. Technology is ripe to tap Earth’s heat. Solar pv is not a solution to reduce CO2 emissions……..According to the International Energy Agency (IEA) 54 x 109 (54 billion ) solar  pv cells are required to generate 14 million Giga-watt-hours of electricity. The amount of CO2  emitted during the manufacture of a single solar pv cell from quartz is 3312 x 106 kg. These are  all facts. Now where are we heading…….reducing CO2 emissions or making countries and  industries rich?? (Chandrasekharam, D. and Ranjith Pathegama, G. 2020. CO2 emissions from  renewables: Solar pv, hydrothermal and EGS sources. J. Geomecha. Geophys. Geoenergy Georesour. Lets us not talk about zero-carbon, 2D, 4D in all the  CoP meetings. Lets us just say energy mix, or use renewable etc. Tagging renewables with zero  carbon emission is a myth. There is nothing like carbon neutral or zero-carbon. 



Views expressed above are the author’s own.


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