Sea changes

Every day, the ocean absorbs about 22 million tons of carbon dioxide, which is about the weight of 15 million hybrid automobiles. Just as you can’t see the carbon dioxide that comes out of your own body each time you exhale, you can’t see the gas as it dissolves into the seas.

Space isn’t an issue, considering that the oceans cover 72 percent of the planet, but there is a problem brewing beneath the waves. Carbon dioxide in the air helps insulate our planet and keep it warm. But there can be too much of a good thing: In the last 200 years, humans have added a lot of extra carbon dioxide to the atmosphere by burning fossil fuels like wood, coal and petroleum to produce energy. Two hundred years’ worth of extra carbon dioxide in the atmosphere has bulked up our carbon dioxide blanket ? and average temperatures around the world are now rising. It’s being referred to as global warming.

The effects of this global-warming gas go beyond the air and land. Much of the carbon dioxide emitted into Earth’s atmosphere ends up in the ocean. Of every 10 tons of the gas added to the atmosphere, two or three end up in the water. The growing emissions of carbon dioxide that human activities add to the air have begun changing the chemistry of the oceans. It’s making them more acidic, a process called ocean acidification.

Acids include liquids like vinegar and lemon juice that taste sour. These materials react with bases ? substances, such as ammonia or baking soda, that feel slippery — to form salts. Water is neutral, which means it’s neither an acid nor a base. Scientists measure acidity using the pH scale; acids have a pH between 0 and 7, and bases between 7 and 14. (Neutral water has a pH of 7.0.)

Ocean water is slightly basic, with a pH of about 8.1, but that number is changing. As the amount of carbon dioxide in ocean water goes up, the pH of ocean water goes down, which means it becomes more acidic. It’s happening now, and it’s happening fast. By the year 2100, if we continue to add the same amount of carbon dioxide into the atmosphere that we are adding now, the oceans will be more than twice as acidic as they were before the Industrial Revolution. The Industrial Revolution began more than 200 years ago and describes the rapid growth of industry.

Stephen Ornes, ScienceNews for kids, 9 March 2011. Full article.

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