August 27, 2013

A Sea of Troubles

I've been working on a story, so my blogging has fallen a bit behind, but a couple of items on ocean acidification caught my eye. For those not as obsessed with climate change as I am, here are two key points to understand. First, the levels of carbon dioxide in the atmosphere have risen by a quarter over the last 100 years, going from 290 to over 400 parts per million. (I think that's right. Maybe it's a third. I never could get that straight.) Second, the ocean absorbs a good chunk of that carbon dioxide, but not without a cost to that benefit, especially if you are one of the bazillions of critters swimming around in a shell.

Increased levels of carbon dioxide are lowering the ph level of seawater. Lower ph levels mean the seawater is more acidic. If you are wearing a shell made out of calcium carbonate, that is very bad news. Acid dissolves calcium carbonate. This affects a wide range of sea life, from coral reefs to starfishes to molluscs to any one of 5,000 species of marine phytoplankton that form the foundation of the oceanic food chain, and oh, by the way, produce half the oxygen on the planet. This is not good news for them or for us.

But wait, it gets better. Turns out all this carbon dioxide in the ocean disrupts another of those cycles of nature that make up the checks and balances of climate. The oceans produce something called marine sulfur component dimethylsulphide (DMS). When this stuff hits the atmosphere, it reacts with oxygen to form sulfuric acid, which can form new aerosol particles that impact cloud albedo and, hence, cool Earth's surface.

Well, guess what? Acidic oceans produce less of this DMS stuff.  This means that any cooling effect from ocean-derived sulfuric acid in the atmosphere is lessened. That means the affects of global warming are not slowed down as much as they could be. More global warming means less DMS which means more global warming.

The effects of global warming in the ocean are like a time bomb waiting to go off. It takes centuries to get there and more centuries to unwind the changes. So even if we reduced carbon emissions to near zero levels -- and we all know that ain't gonna happen, not even close -- we will be feeling the effects of current levels of carbon dioxide for centuries to come. How's that for a legacy?

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