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The other carbon dioxide problem

Greg Studen  |  02/04/09 @ 2:50pm

We are all well aware of the dangers of global warming posed by growing concentrations of carbon dioxide in the atmosphere. In response to the threat, we have embarked on a great international effort to limit the burning of fossil fuels before warming has caused irreversible harm to ecosystems and to our human civilization.

Now evidence is mounting of another danger posed by high atmospheric levels of CO2. Scientists have been noticing that the oceans are becoming more acidic-alarmingly so. The chemistry of this phenomenon is well understood. Simply put, CO2 dissolves in ocean waters and forms a weak acid. As the amount of CO2 grows in the atmosphere, more of it dissolves and steadily increases the acidity of seawater. A good review article in Science Daily discusses the extent of the problem and the damage that it is causing to ocean ecosystems.

The countless marine organisms that build their shells from calcium carbonate cannot function properly in more acidic waters, which cause their skeletons to literally dissolve. The impact on the oceans could be devastating, with potential loss of corals as well as micro-organisms that form the basis of ocean food chains. Increasing acidity will also limit the oceans' ability to absorb additional CO2 from the atmosphere, which will make it harder to control global warming.

Last October a group of leading ocean and atmospheric scientists met in Monaco under the auspices of the Intergovernmental Oceanographic Commission to review the current situation and prospects concerning ocean acidification. Their report, issued on January 30, 2009, as the Monaco Declaration, is a sober warning about the increasing danger to marine resources. The Declaration has been approved by 155 scientists from 26 countries. The text can be found on the Ocean Acidification Network website. Here is their capsule assessment of the risks:

"Ocean acidification could affect marine food webs and lead to substantial changes in commercial fish stocks, threatening protein supply and food security for millions of people as well as the multi-billion dollar fishing industry. Coral reefs provide fish habitat, generate billions of dollars annually in tourism, protect shorelines from erosion and flooding, and provide the foundation for tremendous biodiversity, equivalent to that found in tropical rain forests. Yet by mid-century, ocean acidification may render most regions chemically inhospitable to coral reefs. These and other acidification-related changes could affect a wealth of marine goods and services, such as our ability to use the ocean to manage waste, to provide chemicals to make new medicines, and to benefit from its natural capacity to regulate climate."

The Monaco scientists call on policy makers to take the initiative to "prevent severe damages from ocean acidification by developing ambitious, urgent plans to cut emissions [of carbon dioxide] drastically." They further state: "To stay below an atmospheric CO2 level of about 550 ppm, the current increase in total CO2 emissions of 3% per year must be reversed by 2020. Even steeper reductions will be needed to keep most polar waters from becoming corrosive to the shells of key marine species and to maintain favourable conditions for coral growth."

Current CO2 levels in the atmosphere are approximately 385 ppm. Most scientists believe that we must limit CO2 to a maximum of 450 ppm to avoid a very high chance of warming levels about 2 degrees C., which is assumed to be the maximum that could be tolerated without catastrophic damages. (Some scientists believe that even lower levels of CO2, below 385 ppm, are required.) As the Monaco Declaration concludes,

"[Ocean acidification] is the other CO2 problem that must be grappled with alongside climate change. Reining in this double threat, caused by our dependence on fossil fuels, is the challenge of the century."

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