Climate Change & the Carbon Cycle

Climate change is a global-scale problem that had major implications to human and biological systems. Earth’s climate has operated for millennium within an equilibrium state between the atmosphere, ocean and terrestrial systems.  As the burning of fossil fuels and landscape alterations (such as deforestation and industrial agriculture) have mobilized fossil carbon into the atmosphere, the earth’s carbon cycle has been pushed out of balance.

Human generated climate change can be thought of as an enormous perturbation in the global carbon cycle. Prior to the modern industrial world, the global carbon cycle was determined by events such as volcanism, sea floor rifting, and meteorite impacts.  Now, human activities dictate much of the movement of carbon around the world.  This is because the burning of fossil fuels and landscape change have moved fossil carbon, which was once buried in deep-sea sediments and terrestrial environments, and mobilized it into the atmosphere.  Once mobilized into the atmosphere in forms such as carbon dioxide and methane, greenhouse gasses can change the thermal conductance of the atmosphere, the chemistry of seawater, and the movement of our oceans.

Who is the driver of the global carbon cycle: the ocean or the atmosphere?  To answer this question, we have to look at the mass balance of carbon in both the atmosphere and ocean.  In preindustrial times the atmosphere contained 578 Pg (Pg=Petagrams, 1 Pg=1 billion metric tons) of carbon. Now, the modern atmosphere contains 766 Pg of carbon.  To compare, the global oceans contain roughly 38,000-40,000 Pg of carbon! The oceans contain roughly 50 times more carbon than the atmosphere, which means that the ocean is the driver of the global carbon cycle, not the atmosphere.  This dynamic between the ocean and atmosphere is important to remember when considering modern climate change. 

In modern climate change, the carbon content of the atmosphere is driving changes in the carbon content of the ocean.  This is a large role reversal in the way our earth’s systems naturally operate, and thus modern climate change is an event that has no analogue in the past. The carbon content of our atmosphere is steadily rising.  Our global oceans are slowly absorbing this abundance of atmospheric carbon. And as our globe becomes carbon-enriched, fundamental chemical and physical properties of our atmosphere and oceans are changing.  As many scientists say privately, climate change is a vast global experiment with very uncertain outcomes for human and biological communities.  Only through advanced scientific and industrial research, carbon-free economic restructuring, and a unified public will can the challenge of global climate change be addressed.