Carbon, number six on the periodic table of the elements, is at the very heart of climate change. Here's all you need to know to understand why.
Basis of life
Carbon is the basis of all life on this planet, from the tiniest single cell organism to blue whales and giant sequoia trees. It's a central element in proteins, sugars, starches, fats, cellulose, lignin and more. Carbon-containing compounds are also called organic compounds, as if to underline their importance in our global life systems.
Carbon is the main element in fossil fuels, too. Oil, coal and natural gas are actually the remnants of organisms that lived on Earth millions of years ago. Upon dying, they were transformed over time by extreme heat and pressure into the products we burn today to power our world.
Fossil fuels may have originated from plants, but they are considered non-renewable because they take millions of years to form. Most of today's coal originated 300 million years ago, during the aptly-named Carboniferous Period, when the world was a hot, humid, people-less place.
Unlike most elements on Earth, carbon is very mobile. Vast amounts are constantly cycling between land, atmosphere and ocean.
It moves from atmosphere to land when green plants absorb carbon dioxide from the air and, using the energy of sunlight, turn it into leaves, straw, wood and other plant materials. Left undisturbed, those materials eventually die and rot, and carbon is added to the soil.
Similarly, carbon moves from atmosphere to ocean when plankton - tiny marine algae - absorb carbon dioxide. Plankton forms the first link of an ocean food chain that sustains life all the way up to whales and sharks.
Carbon moves back up into the atmosphere in several ways. Humans and animals emit carbon dioxide when we exhale; it's a byproduct of our bodies metabolizing the carbon-based food we eat.
Plants emit some carbon dioxide back into the air through respiration.
When living things die, some of the carbon in their tissues ends up in the atmosphere through the decomposition process.
And the burning of plant material, whether by wood stove or forest fire, returns carbon to the atmosphere.
There's much more to the carbon cycle, but here's the critical key message: the carbon cycle has been in natural balance for thousands of years. The amount of carbon removed from the atmosphere has been roughly equal to the amount of carbon added. So the level of carbon dioxide in our atmosphere has remained relatively steady.
But all that's changing. By extracting fossil fuels and burning them, we are taking carbon that has been in deep storage for millions of years, safely locked away outside of our carbon cycle, and reintroducing it to the cycle.
The result? Much more carbon is now being emitted into the atmosphere. Plants and plankton aren't able to absorb all that extra carbon back, and so the level of carbon dioxide in our atmosphere is rising. (It was 275 parts per million at the beginning of the industrial revolution and is over 400 today. Half of that increase has happened since I graduated from high school in 1980.) As the level of carbon dioxide rises, so do global temperatures, because carbon dioxide is the main greenhouse gas driving climate change.
What to do
If we hope to slow climate change, we need to stop disrupting our carbon cycle and allow it to recover balance.
To do that, we need to stop burning fossil fuels. We need to keep that carbon safely stored in the ground. (Contrary to what you may have heard elsewhere, the best form of carbon sequestration is not capturing it from smokestacks and pumping it underground; it's keeping it in the ground in the first place.) We need to develop sustainable sources of energy to meet our needs. And eventually we may even need to look at ways to remove all the carbon we've already put into the atmosphere and store it permanently beyond the reach of the carbon cycle.
Easy? No, because today's world has been built around fossil fuel energy. But urgent beyond question or delay, and the foremost challenge of our generation.