Since the Industrial Revolution, the burning of fossil fuels has caused the concentration of carbon dioxide (CO2) in the atmosphere to increase progressively, from about 278 ppm (parts per million by volume) to the current 414 ppm (the average for 2020 at Mauna Loa Observatory, Hawaii). The concentration would be even higher if it were not for the oceans, which currently absorb about a quarter of the CO2 that humans emit into the atmosphere. In return, however, this absorption is causing changes in the chemistry of seawater. When CO2 passes from air to water, it is involved in a series of chemical reactions and equilibria that result in an increase in acidity and therefore a decrease in pH.
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Pelejero C., Figuerola B. & Calvo E. M., 2022. Ocean acidification: trends, effects and what we have left to learn. In: Pelegrí J. L., Gili J. M. & Martínez de Albéniz M. V. (eds.), The ocean we want: inclusive and transformative ocean science, pp. 158-160. Barcelona: Institut de Ciencies del Mar, CSIC. Chapter.
