What Is Ocean Acidification?

Written By Teacher: Greta Stacy

Greta Stacy is a high school science teacher in Doha, Qatar. She has previously taught in Ecuador and the United States.

Teaching about ocean acidification is important because it allows students to see evidence of climate change firsthand. For older students, a lesson on ocean acidification that includes a hands-on lab would be an engaging option. Younger students can also get into the lab with a simpler experiment that still allows them to observe the effects of climate change on the oceans. This could be a difficult subject for some students, as the destruction of ocean habitats could hit close to home.   

Written By: MIT Environmental Solutions Initiative

The MIT Climate Change Engagement Program, a part of MIT Climate HQ, provides the public with nonpartisan, easy-to-understand, and scientifically-grounded information on climate change and its solutions.

Ocean acidification refers to a gradual increase in the acidity of ocean water, caused mainly by human-emitted carbon dioxide (CO2) mixing with the water.

Since the start of the Industrial Revolution in the late 1700s, humans have caused the concentration of CO2 in the atmosphere to rise by more than 40%, through the large-scale burning of fossil fuels and other changes to the environment such as deforestation. A little less than half of this emitted CO2 remains in the atmosphere, while the rest has been absorbed by the land and the ocean. Scientists calculate that the ocean currently absorbs about 30% of the CO2 that humans are emitting.

The Chemistry

The acidity of a liquid is based on the number of hydrogen ions (H+) it contains: more acidic liquids have higher concentrations of H+. When CO2 dissolves in seawater, it combines with water to form carbonic acid. This acid then breaks apart into H+ and another ion called bicarbonate. As more CO2 is added to the ocean, there is a greater abundance of H+, and the water becomes more acidic.