November 25, 2006

Global Warming's Effect on the Ocean

The consequences of global warming on the earth's surface is widely understood: increased and more violent storms, increased drought in many locations and increased floods in others, disappearing glaciers and ice caps, raising sea levels, and higher average temperatures - all which bode poorly for humans and other creatures on the land in near future. What's not so well understood is the effect of global warming on life in the ocean. This month, Elizabeth Kolbert writes a piece called A Darkening Sea in the November 20, 2006, New Yorker which lays out the effects on the ocean and a vast system of life that is now threatened by the additional carbon absorbed by the ocean.

Kolbert explains that acidification is caused by the decrease in the ocean’s pH level due to its uptake of carbon dioxide, or CO2, noting that the ocean, which covers seventy per cent of the earth’s surface, absorbs and releases gases from and into the atmosphere at roughly equal rates. “But change the composition of the atmosphere, as we have done, and the exchange becomes lopsided: more CO2 from the air enters the water than comes back out,” she writes. Kolbert reports that humans have already pumped some hundred and twenty billion tons of carbon into the oceans, to produce a .1 decline in surface pH, which represents a rise in acidity of roughly thirty per cent. “This year alone, the seas will absorb another 2 billion tons of carbon, and next year it is expected that they will absorb another 2 billion tons,” Kolbert reports. “Every day, every American, in effect, adds forty pounds of carbon dioxide to the oceans.” Kolbert writes, “Because of the slow pace of deep-ocean circulation and the long life of carbon dioxide in the atmosphere, it is impossible to reverse the acidification that has already taken place. Nor is it possible to prevent still more from occurring. Even if there were some way magically to halt the emission of CO2 tomorrow, the oceans would continue to take up carbon until they reached a new equilibrium with the air. . . . Humans have, in this way, set in motion change on a geological scale. The question that remains is how marine life will respond.”

Our oceans could be even more changed by global climate change than the lands because in many ways, the acidification of the ocean reverts it to a much earlier stage in evolution with the food chain narrowing to lots of jelly fish and not much more.

Calcifying organisms come in a fantastic array of shapes, sizes, and taxonomic groups. Echinoderms like starfish and calcifiers. So are mollusks like clams and oysters, and crustaeans like barnacles, and many species of bryozoans, or sea mats, and tiny protists known as foraminifera -- the lists goes on and on. Without experiemental data, it's impossible to know which species will prove to be particularly vulnerable to declining pH and which wil not. In the natural world, the pH of water changes by season, and even time of day, and many species may be able to adapt to new conditions, at least within certain bounds. Obviously, though, it's impractical to run experiements on tens of thousands of different species. (Only a few dozen have been tested so far.) Meanwhile, as the example of coral reefs makes clear, what's more importnat than how acidification will affect any particular organism is how it will affect entire marine ecosystems -- a question that can't be answered by even the most ambitious experimental protocol. The recent report on acidification by Britain's Royal Society noted that it was "not possible to predict" how whole communities would respond, but went on to observe that "without significant action to reduce CO2 emissions" there may be "no place in the future oceans for many of the species and ecosystems we know today."

Humans have had such a massive impact on the world, and by the end of the century, our impact can easily cause more extinctions than the meteor that wiped out dinosaurs. It more than time to do what we can to clean up our act on the emissions of CO2 into the atmosphere.

Coda: my friend eRiposte put up a great linky post about global warming the other day that included a wonderful oped by Al Gore. It was definitely worth following every link in that post.

Update: Here's the online copy of A Darkening Sea.

Posted by Mary at November 25, 2006 09:07 AM | Environment | Technorati links |

This is really true, a lot of people are already being ignorant of global warming on the surface so even more people are ignorant about the effects of global warming on our oceans. I've watched an IMAX theatres film called the coral reef adventure and it explains how global warming is killing our marine life. Global warming is moving fast and it has already killed many reefs. It first kills the coral which is a main source of food for many marine animals and as a result it creates a chain reaction of deaths. One day we won't have any marine life to admire and we won't even have any fish or seafood to eat. This is all caused by human beings and if we don't try to reverse it, we'll be in trouble very soon. The government needs to take global warming seriously because it's only a matter of time before something extremely bad happens as a result of it.

Posted by: Stephanie Ngo at November 25, 2006 10:17 PM