Some of the consequences of greenhouse gas emissions have been discussed in the previous sections of this toolkit in terms of rising global sea temperatures, but global warming is not the only threat from increased atmospheric concentrations of carbon dioxide (CO2). Increasing atmospheric CO2 is also changing the ocean’s chemistry. Ocean acidification occurs when CO2 in the atmosphere reacts with water to create carbonic acid, decreasing both ocean pH and the concentration of the carbonate ion, which is essential for calcification.
Although the chemistry of this effect is well understood and not much debated, the full consequences of ocean acidification for marine ecosystems and human well-being are only beginning to be revealed. Warming seas and ocean acidification are already affecting reefs by causing mass coral bleaching events and slowing the growth of coral skeletons, threatening coral reef resilience.
This section of the toolkit provides information on the problem of ocean acidification and the management and policy approaches being considered to combat this global issue.