DREASON: The absorption of human-generated CO2 by the oceans increases the oceanic concentration of carbonic acid because it reacts with water to form carbonic acid, it increases the oceans' acidity and lowers the pH of seawater, reduces the carbonate ion concentration in the oceans and threatens calcifying organisms in marine ecosystems because the absorption of CO2 by the oceans leads to a decrease in the carbonate ion concentration, which is required for calcification, the production of calcium carbonate (CaCO3) by many marine organisms, and increases the hydrogen ion concentration in the oceans but decreases the carbonate ion concentration and threatens the livability of the oceans for calcifying organisms.