The oceans play a vital role in regulating the Earth’s climate, and one of the key factors that affects this process is the level of dissolved carbon dioxide in the water. However, when CO2 levels in the ocean increase, it leads to a decrease in pH levels, causing ocean acidification.

Ocean acidification is a pressing concern, as it affects not only marine ecosystems but also human activities that rely on the ocean, such as fishing and aquaculture. The World Meteorological Organization’s latest State of the Global Climate report highlights the continued decrease in global average ocean surface pH, with the most intense regional decreases observed in the Indian Ocean, the Southern Ocean, the eastern equatorial Pacific Ocean, the northern tropical Pacific, and some regions in the Atlantic Ocean.

The effects of ocean acidification are far-reaching and have been observed in various ecosystems. For example, coral reefs, which are essential for many marine species, are being negatively impacted by increasing CO2 levels. Moreover, the acidification of the ocean surface has led to a decrease in the availability of calcium carbonate, which is necessary for many marine organisms to build their shells and skeletons.

The impact of ocean acidification is not limited to marine ecosystems. It also affects human activities, such as fishing and aquaculture. Shellfish aquaculture, for instance, has seen a decline in production due to the decrease in the availability of calcium carbonate, making it challenging for farmers to maintain their livelihoods.

The World Meteorological Organization’s report also highlights the fact that ocean acidification will continue to increase in the 21st century at rates dependent on future emissions. This means that the effects of ocean acidification will be exacerbated by human activities, leading to further degradation of marine ecosystems and potentially severe consequences for human communities that rely on the ocean for their livelihoods.

The good news is that new ways of studying ocean acidification are being developed, including the use of nuclear and isotopic techniques by the International Atomic Energy Agency’s environmental laboratories in Monaco. These new methods will provide scientists with a better understanding of the causes and effects of ocean acidification, ultimately leading to more effective conservation and management strategies.

As the researchers say: “Ocean acidification research is a high priority today considering the dangerous coincidence of past acidification events with mass extinctions and global biodiversity crises.”

The nickname “evil twin” is often used to describe ocean acidification, highlighting the similarity between the current event and past acidification events that led to mass extinctions and global biodiversity crises. This nickname is a stark reminder of the gravity of the situation and the need for urgent action to mitigate the effects of ocean acidification.

The geological record can provide valuable information for understanding past ocean acidification events. A recently released study in Evolving Earth reviewed proxy measures from the fossil record that can be used to understand past ocean acidification events.

Ocean acidification has increased by around 30% compared to pre-industrial levels, an increase that has occurred over several hundred years. This increase has occurred instantaneously in the geological record, highlighting the urgency of the situation.

The impact of ocean acidification is not limited to the past; it is a pressing concern for the present and future.