Overview

What is happening to our oceans?

The acidity of liquids is specified by a pH value – the lower the pH value is, the more acidic the liquid. The pH value of near-surface seawater is currently around 8.1 on average worldwide, having already fallen by around 0.1 compared to the preindustrial era. While this change might sound insignificant, it translates to a 26 percent increase in acidity (because the pH scale is logarithmic). Among other things, this development threatens numerous calcifying marine organisms, such as corals, mussels, and crabs.¹

The reason behind the “acidification” of the world’s oceans is carbon dioxide released by human activity into the atmosphere. Since the 1980s, the oceans have absorbed around 20 to 30 percent of these emissions.² When CO2 dissolves in seawater, it reacts with water to form carbonic acid. If carbon dioxide emissions resulting from human activity do not decrease, the pH value could drop by the end of the century to levels not seen in the oceans for more than 50 million years.³ Corals are also suffering greatly from the rising ocean temperatures.⁴

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¹ IPCC 2013, AR5, WG 1, SPM, B.5 – https://www.de-ipcc.de/media/content/AR5-WGI_SPM.pdf
² IPCC 2018, SROCC, SPM, A.2.5 – https://www.ipcc.ch/srocc/chapter/summary-for-policymakers/
³ IPCC 2013, AR5, WG 1, Kapitel 3, Box 3.2 – https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter03_FINAL…
⁴ IPCC 2018, SROCC, SPM, A.6.4 und B.5.4 – https://www.ipcc.ch/srocc/chapter/summary-for-policymakers/