Summer 2011

Dialogue | Why is ocean acidification caused by global warming such a serious problem?

Our world’s oceans help regulate the global climate by absorbing carbon dioxide (CO2) from the air, and research has shown that the oceans have not only absorbed about 30 percent of human-caused CO2 emissions over the last two centuries, but also continue to absorb about 1 million tons per hour. However, as this CO2 is absorbed, seawater becomes more acidic. Since the Industrial Revolution of the mid-1800s, Earth’s oceans have become 30 percent more acidic.

CO2 depletes carbonate ions in seawater, leaving fewer ions free to build the calcium carbonate-based shells and skeletons of organisms known as calcifiers: corals, crustaceans (e.g., shrimp), echinoderms (e.g., starfish), and mollusks (e.g., clams). This could have a devastating impact on biodiversity and the food chain, as millions of organisms depend on coral reefs for shelter, and on other calcifiers for food.

While ocean pH levels have fluctuated over time, acidity levels have increased at a much more rapid pace than in the past, and will continue to worsen if our CO2 emissions continue unabated. And it should be noted that proposed “geoengineering” solutions to global warming, such as injecting light-reflecting particles into the atmosphere, would do nothing to halt ocean acidification even if they succeeded in reducing temperatures (which is not a given).

The surest way to avoid the most dangerous impacts on marine ecosystems is to shift quickly to energy sources that produce less CO2.


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