The impact of man’s fossil fuel burning and deforestation on Earth’s climate can hardly have escaped anyone’s attention. But there is a second, much less known, consequence of our carbon dioxide (CO2) emissions. A large part of human-caused CO2 is absorbed by the world’s oceans, where it affects ocean chemistry and biology. This process, known as ocean acidification, is also referred to as “the other CO2 problem”.
The oceans as a sink of CO2
The oceans, covering 70% of Earth’s surface, provide a number of services to human society such as oxygen production (50% of the oxygen available in the atmosphere is produced by the oceans), source of food, income and recreation, and play a major role in the regulation of Earth’s climate. In fact, one fourth of human-caused carbon dioxide (CO2) emissions are absorbed by the oceans, translating into 24 million tons of this greenhouse gas taken up by the oceans each day. Around one third of our emissions are absorbed by the terrestrial vegetation while roughly 45% remain in the atmosphere, where their accumulation leads to climate change. It is not hard to imagine the consequences if the oceans were too lose their ability to take up part of the anthropogenic CO2 released. But what is the result of adding increasing amounts of CO2 to the ocean? A perturbation of the very chemistry of seawater — a phenomenon known as ocean acidification.