Day 64: The Carbon Cycle – how do humans affect it? (Part 2)

Like I mentioned in Part 1, the scary part about analyzing the carbon cycle is realizing how much humans are affecting it. If we look at the diagram of the carbon cycle, one of the ways carbon transits from sphere to sphere is from the subsurface (fossil fuels) to the surface by extraction, then to the atmosphere by burning the fossil fuels. The atmosphere also exchanges with the hydrosphere, so part of the carbon that we burn is then absorbed by the ocean.


The Carbon Cycle. Source: University of New Hampshire, 2008

Only that’s where things seem to get a little tricky. There’s only so much that the atmosphere can handle. It can divert carbon to plants and to the ocean, but only as much as the plants or the ocean can absorb. And that’s getting harder. Here’s a hint – the more deforestation there is, the harder it is for the excess carbon dioxide to be ‘drained’ from the atmosphere through plants, and the more oceans absorb carbon dioxide, the less readily it accepts more carbon dioxide. The excess is piling up in the atmosphere. That’s why scientists and concerned environmentalists are so worried about the levels of carbon dioxide today in the atmosphere – at more than 400 ppm, they’re astronomical and probably unprecedented within the last 400 000 years at least.

The oceans are also taking in more than they can handle. Carbon will only leave the oceans to return to the atmosphere or to become a component of sea shells (calcite), and then it will eventually be buried in the ocean floors when the sea organism dies. But sea shells can only control so much carbon – the rest is stocking up in the ocean, turning it more acidic, less likely to absorb more carbon dioxide from the atmosphere, and more dangerous to sea-life.

We’re disrupting a natural cycle by burning stocks of carbon that were in the ground and releasing them elsewhere in the Earth’s systems. The organisms that depend on the integrity of this cycle (basically, all life on Earth) will be affected by the consequences of disrupting the carbon cycle –  such as global warming, ice melt, ocean acidification, sea-level rise, changing weather patterns, loss of habitat to name a few.

One of the reason I’m writing and thinking about this is because teaching the carbon cycle is in the Next Generation Science Standards for Earth Science, and there is no way the teach the carbon cycle without it being glaringly obvious that humans have interfered with this cycle. Looking at actual data is pretty shocking.

The other reason I’m thinking about this is because I’ve heard people say “Humans aren’t that powerful – humans can’t affect the way the Earth works! The Earth will go through global warming independently if humans burn fossil fuels or not.”

The response to that is: Sadly, humans (and other organisms on Earth) ARE that powerful that their actions can have planetary consequences.

Stay tuned to see more of those planetary consequences in Part 3.


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