Acidifying the Ocean
CO2 is an acid, with which humankind is acidifying the oceans. In response, CaCO3 (a base) will dissolve on land and in the ocean, restoring the pH balance of the ocean. This process will take thousands of years. As the pH of the ocean recovers, the change in ocean chemistry will extract some of the fossil fuel CO2 from the atmosphere, but even after the pH recovery is complete, models of the carbon cycle predict that about 10% of the fossil fuel CO2 will remain in the atmosphere, until it is consumed by the weathering thermostat, which stabilizes the climate of the Earth on a timescale of hundreds of millennia, as described in Chapter 6
Acidity is a property of water-based concoctions like seawater or rainwater. An acidic solution contains a high concentration of positively charged hydrogen ions, H+. Hydrogen ions are aggressive little guys, reacting quickly and harshly with many kinds of chemical bonds, including bonds in metals, rocks, and biological carbon compounds. Your digestive juices are acidic, to aid the breakdown of the chemical bonds in your food. Battery acid is so acidic and reactive that it is dangerous; a splash will burn you.
H+ can be extracted from a water molecule, leaving behind a remnant called hydroxyl ion, OH−: