Читать книгу Climate Change For Dummies - Elizabeth May - Страница 44

The ocean is the biggest carbon sink on Earth. So far, it has tucked away about 90 percent of all the carbon dioxide in the world. If that gas was in the atmosphere, not underwater, the world would be a lot hotter.

The exchange of carbon dioxide between the ocean and the air happens at the surface of the water. When air mixes with the surface of the ocean, the ocean absorbs carbon dioxide because carbon dioxide is soluble in water (that is, carbon dioxide can be absorbed by water). And, in fact, the seas’ ability to absorb carbon dioxide is referred to as the solubility pump because it functions like a pump, drawing carbon dioxide out of the air and storing it in the ocean.

The ocean also acts as a biological pump to remove carbon dioxide from the atmosphere. Plants close to the surface of the ocean take in carbon dioxide from the air and give off oxygen, just like plants on land. (We discuss this process, known as photosynthesis, and the role that plants play in the carbon cycle in the following section.) Phytoplankton are microscopic plants that live in water. You may know them as algae, most commonly seen as the greenish clumpy plants that float around on ponds and other water. Phytoplankton have short but useful lives. If other organisms don’t eat them, they simply die within just a few days. They then sink to the ocean floor, mix into the sediment, and decay. The carbon dioxide that these plants absorb during their brief lives is well and truly sequestered after their little plant bodies are buried.

Each year, the oceans put away about another 2 billion metric tons of carbon dioxide. Figure 2-3 demonstrates how the ocean interacts within the carbon cycle. According to the World Economic Forum, recent research suggests that the 2 billion metric tons of carbon a year may actually be an underestimate. It could be as much as .9 billion metric tons more — every single year. Sometimes it’s expressed as ten Hiroshima-size nuclear bombs worth of energy in heating — absorbed by the oceans per second. Scientists writing about the huge amount of energy stored by the oceans search of explanations in equivalents that people can grasp — like nuclear bombs. That’s because the science is expressed in unfamiliar terms. Describing the energy in terms of nuclear bombs is a scientist’s way of expressing that the ocean absorbed 20 sextillion joules of heat in 2020.

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FIGURE 2-3: The relationship between carbon dioxide and the oceans.