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Posted at 10:30 AM ET, 07/07/2008

Freedman: Ocean Acidification - The Sleeper Issue

If I were to rank climate change impacts in terms of sexiness or pizazz, ocean acidification would rank near the bottom of the list. The relatively slow, unseen process would be well behind the drama of highly visible shifts such as more intense hurricanes, severe droughts, and melting sea and glacial ice.

However, although ocean acidification isn't generating headlines as much as these other climate-related problems are, some scientists are regarding it as just as significant of a threat, if not more so.

Keep reading to learn why acid is bad for the ocean. For the short term weather outlook, see our full forecast.

According to a report published last week in the journal Science, ocean acidification is such a potentially damaging effect of climate change that it should be considered as a key element of any plan that sets carbon dioxide emissions reduction targets. In fact, the article states, avoiding damaging ocean acidification may require making more significant emissions cuts than what is currently deemed politically expedient.

In order to understand ocean acidification, one must know a little bit about the role of oceans in the climate system.

The oceans are the biggest carbon "sink" on the planet, since they absorb, through chemical processes, much of the CO2 that is emitted from land-based sources. The oceans have soaked up a staggering amount of carbon dioxide in the past 200 years -- about 40 percent of what humans have put into the air from the burning of fossil fuels and other activities, according to four researchers led by Richard Zeebe of the University of Hawaii. That's great for the atmosphere, which needs such a repository for carbon dioxide in order to prevent catastrophic warming, but it doesn't bode well for certain marine ecosystems.

As oceans take in more carbon dioxide, the pH value of the water is lowered. The study in Science magazine states that oceans have already become more acidic, by about .1 pH units since the start of the industrial revolution. If greenhouse gas emissions were to continue to increase, the study states the ocean's pH could drop by as much as .2 to .3 pH units, which is regarded as especially dangerous. The time frame within which such a drop would occur depends on the amount and rate of future carbon dioxide emissions. Such increasing acidity would potentially imperil many marine organisms such as corals, mussels, and oysters.

As water gets more acidic, it weakens the ability of certain marine organisms to build their protective shells and skeletons. Many of the organisms that lie at the base of the marine food web depend on calcium carbonate minerals to form their shells, but acidic water alters the quantity and endurance of these minerals.

Zeebe's article states that the public and decision makers need to be much more aware of the changing chemistry of the oceans, and may need to establish tougher emissions reduction targets to take into account the sensitivity of marine ecosystems to fluctuations in the pH level.

"Ocean chemistry changes, and not only climate effects, should be taken into consideration when determining carbon dioxide emission targets; such consideration is likely to weigh in favor of lower emission targets," the article states.

Much remains to be discovered about the sensitivity of different species to acidification, but scientists know enough to be worried.

"We know that ocean acidification will damage corals and other organisms, but there's just no experimental data on how most species might be affected," said co-author Ken Caldeira of the Carnegie Institution's Department of Global Ecology in a press release.

"Most experiments have been done in the lab with just a few individuals. While the results are alarming, it's nearly impossible to predict how this unprecedented acidification will affect entire ecosystems,"

Perhaps the fact that emissions of greenhouse gases from human activities are being seen everywhere from Arctic ice down to the molecular composition of the oceans will be enough to convince some people that climate change needs to be dealt with. But mounting an awareness effort around ocean acidification is a challenging endeavor, because at the end of the day unless a person's income depends directly from marine ecosystems, it would be difficult to show that it would affect them in more ways than just what they find on the menu the next time they go to Legal Seafoods.

For now, I'll keep it in the category of "dull but worrisome" on my list of climate-related calamities, unless any readers can convince me otherwise.

By  |  10:30 AM ET, 07/07/2008

Categories:  Freedman, Freedman

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