The ocean is our global heat reservoir and one of two major carbon dioxide sinks. If you agree that humans are trapping heat and carbon dioxide in the planet's atmosphere — and 53 years of rigorous observations at Scripps and other research institutions show that we are — then the ocean must be at the very center of the climate discussion. But it rarely is.
Consider Cancun: The negotiation text presented at the outset of the climate conference contained exactly one passing reference to the oceans, submerged in a Mariana Trench of footnotes.
Our stubborn addiction to burning coal, oil and natural gas is changing not only the composition of the atmosphere but the composition of the ocean as well. The carbon dioxide those fuels pour into the air inexorably dissolves into the oceans, causing a process known as ocean acidification. The oceans have absorbed 30% of the carbon dioxide that humans have ever produced, and they continue to absorb more each year.
This force-feeding has changed ocean chemistry. As carbon dioxide is added to the ocean, it increases the amounts of dissolved hydrogen-carbonate ions and hydrogen ions (and hence acidity) but decreases the amount of carbonate ions. By the end of the century, acidity will probably double from today's levels, unless we stop pouring carbon dioxide into the atmosphere.
The increasingly scarce carbonate ions are the very ones marine invertebrates combine with calcium ions to make their shells. Ocean acidification has been likened to an accelerated case of osteoporosis that afflicts creatures such as massive coral reefs and pteropods — tiny snails that are a key food of commercially important fish. There is also evidence that increasing acidity disrupts the juvenile development of a variety of marine organisms, including clownfish and krill. Marine organisms are wonderfully suited to adapt to changes in seawater chemistry, but never before in history have they been asked to do this so quickly.
Marine scientists in various countries, including China, Germany and the United States, are engaged in a variety of national research programs focusing on the important biological impacts of ocean acidification. We need to document which fisheries, coral reefs and marine ecosystems will be affected first, and how long they might take to recover (if at all). That takes time, but don't be fooled by the pat response: "We need more research first." We know enough to act now.
Last month, the Environmental Protection Agency issued a memorandum encouraging coastal states to start developing assessment methods for evaluating marine waters based on ocean acidification. But assessment is not enough.
Nor should we think we can rely on innovation and geo-engineering to stop acidification. Some have suggested sunshades for the Earth, but that will neither repair the oceans' chemistry nor reverse the changes that have occurred thus far, let alone protect against our continuing release of carbon dioxide. Another suggested antidote — deliberately modifying the oceans' microbial cycles of carbon and oxygen so as to interrupt acidification and allow us to continue our current fossil fuel addiction — would be an act of hubris and desperation. We have a clear and attainable alternative: making electricity without releasing carbon dioxide.
Our oceans serve as the primary source of protein for a billion people. We use them for transport, recreation, vacation and inspiration. Microbes in the oceans make 50% of the oxygen we breathe, as well as omega-3 fatty acids that make their way into our food and help us stay healthy. Their waves and winds may soon help us create clean energy. And yet we load them full of trash, tolerate catastrophic oil spills and ignore the impact on them of climate change and carbon dioxide waste.
It is time we paid respect to this great communal resource and stopped using it as a dump. It's time we put oceans front and center in the political climate debate. And it's past time we stopped pouring carbon dioxide into our air and seas.
Tony Haymet and Andrew Dickson are professors at Scripps Institution of Oceanography, UC San Diego, in La Jolla.