It’s Still a Wonderful World

Greetings, readers! I hope this week’s article brings a bit less brain and a little more heart.

            I hope I don’t appear as though I don’t care about the Monument Fire and River Complex by writing this science column in a somewhat “ostrich with her head in the sand” manner. I care very much about the current events unfolding in these mountains. It’s all I think about, why I decided to speak up and write in the first place. My heart breaks for all those displaced, who have lost homes and are surviving the chaos of destruction and evacuation as best they can.

There is little more I can say beyond what has been written in the feature fire articles and the informative pieces offered by longstanding TC columnists. All I can add is that I am so sorry this is our shared reality and that there is been so much suffering. I’m inspired to see the way helpers spring forth from this community to care for their own. The fires of this season will not burn for eternity. The firefighters and residents of this county will do everything they can to see that these fires go cold. I hope this short article is a brief reprieve from pain.

            Today we’ll review and recollect. We know Earth is a round planet, spinning on its axis, orbiting the sun. This means that sunlight reaches Earth’s surface at different angles: the equator receives direct sunlight over a smaller, more concentrated area, and the latitudes and poles receive light at lower angles that are less direct and allow the beams to spread over a larger geographic area. Here’s a helpful refresher: https://en.wikipedia.org/wiki/Effect_of_Sun_angle_on_climate. We have climate zones (tropical rainforests, mid-latitude deserts and grasslands, arctic tundra, polar ice caps) because of these variations in solar energy striking Earth’s surface.

            We also know that materials can move from place to place (sphere to sphere) through chemical reactions or phase changes. Just as water moves between the sky and water bodies (atmosphere and hydrosphere), carbon moves between the atmosphere, biosphere, hydrosphere, and lithosphere by taking the form of CO2, methane, hydrocarbons, and carbonate rocks (limestone and marble). A tree or brick of coal becomes atmospheric CO2 through the chemical reaction of combustion, and CO2 becomes biomass (trees, calcium carbonate planktonic shells) via photosynthesis. In summary, energy and materials are constantly flowing from place to place around the planet in perpetuity, and at varying rates (days to hundreds of millions of years).

            We also know Earth is a complex system with time lags (processes don’t happen instantaneously), non-linear (mostly exponential) relationships, and built-in feedback loops that can either amplify (increase) a change in the system, or dampen (decrease) a change in the system. We know from direct observation and from ancient climate records that Earth doesn’t usually react in a predictable, linear way. There are numerous of examples of a forcing (a change in the system) going undetected for a good long while (the flat part of the exponential curve), but then suddenly manifesting in a rapid, lightning-fast flip into a new equilibrium (the steep, rocket-ship trajectory part of the exponential curve).

I grew up in New Hampshire. Before I was born, acid rain was falling from the sky and filling the lakes. Rather than having the fish die off in a gradual manner, with the death count increasing year after year, they survived for years with no apparent change in their population. Then, in the course of one summer, there was a massive fish die-off in the lakes that happened all at once, seemingly without warning. Once the waters were tested, scientists understood that the fish had been chronically poisoned, and then were pushed past the threshold of survival when the water became too acidic for sustained life and procreation.

            We live on a miraculous, one-of-a-kind planet that is awesome and fearful in its complexity and interconnectedness. As John Muir once wrote, “When we try to pick out anything by itself, we find it hitched to everything else in the Universe.” If we can better understand these nuances and intricate relationships, we can better care for and nurture this spectacular Earth. Agapé.

The Slow Carbon Cycle: Long-Term Climate Thermostat

Let’s delve into the slow carbon cycle!

Fluxes include: respiration and photosynthesis (between the biosphere, hydrosphere, and atmosphere), sedimentation and metamorphosis, (between the biosphere and lithosphere), weathering, erosion, volcanism, and fossil fuel combustion (between the lithosphere and atmosphere), dissolution and outgassing (between the hydrosphere and the atmosphere), and precipitation, melting, evaporation, and sublimation (between the cryosphere, hydrosphere, and atmosphere).

When plants photosynthesize, they “inhale” CO2 and combine it with sunshine to produce sugars and oxygen. 6CO2 + 6H2O —> C6H12O6 + 6O2. (Plankton in the ocean create calcium carbonate (CaCO3) shells). Photosynthesizers literally build plant matter and tiny shells out of atmospheric CO2, storing it in their biomass. How neat is that? Plants, trees, and plankton are therefore carbon sinks, meaning they remove atmospheric CO2 and store it in a woody/leafy/carbonate shell form. When plants, trees, and plankton die, they degrade and decompose, thus succumbing to the reverse process and releasing CO2 back into the atmosphere.

Think of a carbon sink like a literal sink: the only way to drain the atmospheric bathtub of CO2 is to open a drain, or to store the carbon somewhere that is not the atmosphere. Biogeochemical cycles are the fluxes to other reservoirs.

If biomass becomes buried (undergoes sedimentation) and is subjected to intense heat and pressure (undergoes metamorphosis) instead of respiring into the atmosphere, it can become: limestone rock that precipitates from the sediments produced by dead plankton, oil or natural gas(plankton metamorphosing under different temperature and pressure regimes and in different geologic formations), or coal (buried trees, usually having decayed anoxically in ancient swamps). Technically, limestone precipitates from the biogenic material in seawater, and quick note, marble is metamorphosed limestone.

Metamorphosis occurs deep within the lithosphere, specifically the aesthenosphere: the boundary between crust and mantle. The lithosphere is therefore also a carbon sink, as sedimentation, metamorphosis, weathering, and erosion are the fluxes that take up to hundreds of millions of years, to unfold, but allow the geosphere to store the largest amount of carbon. An estimated 65,500 billion metric tons (a billion in scientific notation is 1 x 10^9) are stored in the crust and aesthenosphere as sediments, and sedimentary and metamorphic rocks (https://earthobservatory.nasa.gov/features/CarbonCycle).

Weathering and erosion (the mechanical and chemical breakdown of rocks), transports carbon from the atmosphere to the lithosphere via a brief stop in the hydrosphere! Rainwater dissolves CO2, forming a weak carbonic acid that erodes the lithosphere over many hundreds of millions of years. Geoscientists call this “atmospheric scrubbing” because the more CO2 in the atmosphere, the more acidic the rainwater. And remember, more CO2 —> higher temperatures —> more active hydrological cycle —> more atmospheric carbon scrubbing. This is an example of a negative feedback loop, meaning the increase of CO2 leads to an increase in weathering, which dampens the effect of warming caused by the initial increase in CO2. Chemical weathering is one of the greatest, long-term (again, HUNDREDS of MILLIONS of years, an astronomically long time) correcting mechanisms for when Earth’s atmosphere finds itself with excess CO2. But unfortunately for humans, it doesn’t operate on a timescale that can benefit us and our survival as a species this upcoming century. Additionally, mountain building events, like the collision of the India subcontinent and the Eurasian plate causing the uplifting of the Himalayas, are needed to spur on weathering by providing fresh rock surfaces. Plate tectonics is also, you guessed it! an extraordinarily slow geologic process.

Dissolution and outgassing are intuitive. Gases can either dissolve into a solution (like water), or they can be released from a material in which they were frozen, dissolved, trapped, or absorbed. We know the hydrological cycle quite well, so won’t waste more time here.

The slow carbon cycle (metamorphosis, weathering, erosion, sedimentation) acts as a climate thermostat by keeping the atmospheric amount of CO2 relatively stable, within a certain range of values.

We’re piecing it all together . . .

Quick thank you to Dr. Tom Brandes and Trinity Bob for mentioning Eunice Foote’s work in the 1850s discovering the heat-trapping properties of carbon dioxide!

Image sourced from: http://euanmearns.com/the-carbon-cycle-a-geologists-view/