Atmospheric carbon dioxide (CO2) is currently at about 400 ppm; and is the known number-one greenhouse gas (GHG) causing global warming induced climate change.
Previously, overly-abundant CO2 in air caused the Fifth Extinction of about 55 million years ago, [ ] marked by an increase of atmospheric CO2 levels to nearly1000 ppm  largely due to volcanism and the subsequent release of methane vapors resulting in global warming devastation as fossil and geological records indicate [ ] but a continuous threat to life on the planet gradually disappeared over time with natural solutions perfected over millions of years.
Biogeochemically-trapped CO2 forms long-term storage systems in stratified carbonate accompanied by cave environments.
They may be ideal sites for accelerated CO2 storage by naturally enhanced air fluid flow increasing mineral fluid reaction rates.
One obvious solution is
Traffic air, Shanghai, China
CO2 steadily increases along with other combustion aerosols, to extreme levels due to an atmospheric event known as heat inversion.
The phenomena can seriously affect mega-city locations beneath higher terrain where stalled masses of cool air trap warmer city air. Example locations include:
- Greater Los Angles and Salt Lake City in the U.S.;
- Mexico City;
- Nepal's Katmandu, and one of the worst affected,
- Outer Mongolia's Ulaanbaatar. 
Located on or near stratified limestone, a city in the vicinity of a cave may continuously remove atmospheric CO2 from the water cycle while mitigate point-source emission.
Ground waters stream through caves and rain event runoff forces indirect entry by seepage from saturated over-burden dissolving calcium carbonate to aqueous cations,
Rain containing carbonate ions (CO3^2-)
Atmospheric CO2 follows the water cycle. The hydrosphere cycles water between biosphere, lithosphere and atmosphere. 
Category of the action
What actions do you propose?
Untreated CO2 from industry and transportation sectors accumulate daily along with other hazardous post-combustion gases, in pollution plumes over most cities [ ][ ]
Cave environments are natural CO2 traps for long-term carbon storage evidenced by mineral carbonate precipitates. Vertical thermal gradients and variables of atmospheric pressure influence volume air exchanges functioning through vents open to the atmospheric boundary layer.
By experiments, Subterranean arteries with flowing calcium and carbonate ions deposits are manipulated forcing additional carbonate formations, aerosol storage, and long-term CO2 removal from the hydro-cycle.
marine foraminiferan, microscopic single-celled protists shells fall from the sunlit surface into the sea-floor mud forming chalk-deposits over geological time.
A single 6-inch cube of chalk from the White Cliffs of Dover in Southern England contains over 1000 liters of compressed CO2 from the Cretaceous atmosphere. [6, 7]
geochemical weathering, [ ] gradual erosion due to any amount of CO2 molecules dissolving into water as rain falls through the air. portions of dissolved CO2 consolidate forming weak carbonic acid that saturates the landscape. With more CO2 aerosols, more hydrated carbonate ions enter wet terrestrial and subterranean realms, form global acid-base reactions and paragenesis resulting from common metasomatic rock alterations by hydrothermal deposits of dissolved mineral elements.
nd bicarbonate (HCO3-) in equilibrium is unbalanced on contact with mineral and subterranean calcium, potassium, sodium, or magnesium sediment salts and breakdown or formation reactions occur. reactions occur due to dissolved carbonate and bicarbonate medium amphiprotic, meaning solution can function as acid or base depending on pH. Groundwater pH between 5.6 and 10 influencing ion balance. carbonates will either break or form. Lower pH dissolves carbonate and higher pH will reduce carbonate solubility to precipitate carbonate.
Groundwater's dissolved Ca2^+ , CO3^2-, HCO3- , H2CO3 are carried by gravity to cave ceiling and drip calcium ions acquired by progressing through the overburden, results, carbonate formation, long-term removal of CO2 from vertical distributed saturation and precipitating stalactites/stalagmites growing 1-mm diameter annually. [12, 13]
Who will take these actions?
Carbonate deposits and cave formations are extensive layers of solidified minerals with dissolved mineral voids, both are common stratified layers found world-wide. For example, limestone or calcium carbonate is widely distributed on every continent
Artificial carbonate dissolution, precipitation, and mineral fusion
By comparison, vaporous CO2+H2O in an exhaust environment experiencing a region of higher pH, becoming exposed to metal salts, and the breakdown reaction is reversed. A formation reaction precipitates carbonate  and sediments are fused forming porous mineral solid.
Where will these actions be taken?
In the United States, government standards have not kept pace with airborne contamination in the most troubled urban areas. There are no established regulations or current legislation mandating mechanisms to scrub tailpipe gases before they enter the ambient air or after.
Natural carbonate dissolution, precipitation, and mineral fusion