Climate Models and the Carbon Cycle

The carbon cycle:

To tell the story from the beginning, consider the carbon atom – 6 protons, 4 valence electrons, 4th most abundant element in the universe – basis of all life on earth. It’s locked up in rocks and plants, dissolved into our oceans, and mixed up with other gases in our atmosphere. As rocks it shows up as coal, limestone, or graphite for instance. In the rivers and oceans it’s mainly carbonic acid. In the atmosphere, carbon dioxide and methane gas.

While on the whole, restorative chemical processes [1] keep the relative distribution of carbon among these reservoirs fairly stable, each individual atom of carbon is in motion, traveling between the various phases, from gas to liquid to solid, between atmosphere and oceans and rocks and living matter. This is what’s known as the carbon cycle.

carbon_cycle_1

A carbon cycle drawn by: Courtney Kesinger

The carbon cycle has various loops, none of which is completely closed. For instance, in the fast carbon cycle, which is traversed on the time scale of a human life, carbon is taken up from the atmosphere by plants through photosynthesis, stored as sugars, then released back into the atmosphere when it is burned for energy, either by the plant itself, or by something that has consumed the plant, such as an animal, a microbe, or a fire.

But this loop is not closed. Dead plant matter which is buried before it has time to decompose do not release their carbon back into the atmosphere as a part of this fast cycle. Instead, it becomes coal, or oil, or natural gas, and is locked up for millions of years beneath the earth’s surface.

Before the industrial revolution, carbon stored in fossil fuels found its way into the atmosphere mainly through volcanic eruptions, as a part of the slow carbon cycle–called this, because a round-trip takes roughly 100 million years. In this leisurely cycle, rain dissolves atmospheric carbon, forms a weak acid – carbonic acid – which it then deposits into lakes and rivers and oceans. These ions are collected undersea by living organisms and built into shells. Carbon, now in solid form, settles to the sea floor when these organisms die, and builds up sedimentary rock layer by layer. Finally, the earth’s heat melts these rocks, and volcanoes and hot spots return carbon (including that which is contained in fossil fuels) to the atmosphere.

A key point about these natural processes is that they are roughly in balance. For instance, the rate of carbon release into the atmosphere, by respiration or volcanic activity, is matched by the rate of carbon absorption into plants and oceans. And this system is held in approximate equilibrium by various restoring forces. A sudden, small increase in the concentration of carbon in the atmosphere, absent other factors, leads to increased plant growth [2], more rain [1], and more direct absorption at the surfaces of oceans [3]. In other words, the oceans acidify to deplete this extra carbon.

But how much carbon can our oceans take up? When, if ever, would the climate then return to its pre-perturbed state? What would the earth look like in the interim, in the far term?

By unearthing and burning fossil fuels, in our cars, factories, and electrical plants, we are harnessing energy by shortcutting a process which naturally occurs on geological time scales. About 30 billion tons of carbon dioxide are now added per year into the atmosphere directly by the burning of fossil fuels [5]. A rate 100 times greater than that of volcanic emissions. As a result, atmospheric carbon, according to ice-core records which go back 800,000 years, is at its highest ever level [4].

 
Climate models:

We can use physical models to predict how the earth’s climate system might respond to different stimuli. To understand climate models, consider how a physical model can be used to predict the orbital motion of the planets. Given a set of parameters which describe the system (the position, mass, velocity of the planets and sun), the physical laws which govern the system (Newtonian physics or, more accurately, General Relativity), a certain set of simplifying assumptions (a planet’s interaction with another planet is insignificant compared to its interaction with the sun), and what emerges is the “future” of these original parameters. Some won’t change, such as the masses of the bodies, but others–their positions and velocities– will describe a trajectory.

Similarly, climate models aim to plot a trajectory for earth.
 

bbspec

Black body radiation of the sun and earth after traversing the atmosphere.


How well such a model performs depends crucially on the validity of its assumptions and completeness of its knowledge–our knowledge. Afterall, they know only what we know. We know, for instance, that earth exchanges energy with outer space through radiation, or light. We know that carbon dioxide and methane strongly absorb and re-emit certain IR frequencies of light while remaining largely transparent to visible frequencies. When incoming radiation is visible light (sunlight) and outgoing radiation is IR, we expect that an increase in greenhouse gases leads to an imbalance favoring energy influx over outflux. And, as Dr. Scott Denning stated in an earlier post: “When you add heat to things, they change their temperature.”
 
penguins

Tiki the Penguin

A deeper question is where the extra energy will go. To that end, we model the earth’s land, oceans, ice sheets, and atmosphere, allow them to absorb energy as a whole and exchange heat with each other through various thermodynamic processes. We track their temperatures, their compositions, and their relative extent. In this way, we can get a rough idea of the global response to a given amount of energy imbalance, called “forcing”.

But it gets more complicated.

The response itself may alter the amount of external forcing. The loss of ice sheets decreases the earth’s reflectivity, increasing the planet’s energy absorption [7]. The thawing of permafrost and prevalence of hotter air are likely to elevate, respectively, levels of methane [9,10] and water vapor [12]–two additional greenhouse gases–in the atmosphere. These are examples of known feedback mechanisms.

If the planet’s response to an energy flow imbalance is to increase this imbalance, the feedback is positive: climate change accelerates. On the other hand, negative feedback slows further climate change by re-balancing the earth’s energy flux. Changes in the carbon cycle, as in the ocean’s acidification by CO2 uptake, is one example of negative feedback [1]. So far, about half of our CO2 emissions have found their way into our oceans [13].

It’s in this tug-of-war between positive and negative feedback mechanisms that the trajectory of earth’s future climate is drawn [8]. Ultimately, thermodynamics guarantees that the earth’s climate will find stability [11]. But we shouldn’t confuse a planet with a balanced energy budget with a necessarily healthy or habitable planet. Venus, for instance, has a balanced energy budget, and a composition very similar to earth. In other words, the question is not whether, but where.

The crucial role that climate models play in all this is that they help us catalogue and combine these separate pieces of knowledge. The more perfect the information, the more accurate its predictions. Right now, improving future accuracy of climate models depends heavily upon getting a good grasp of climate feedback mechanisms. As we slowly step toward a more complete understanding of our climate system, it’s important we continue to receive new science in context, reminding ourselves that each new study is a welcome refinement of our knowledge, that neither proves nor disproves global warming– simply moves us forward.

 


[1] http://earthobservatory.nasa.gov/Features/CarbonCycle/
[2] http://www.climatecentral.org/news/study-finds-plant-growth-surges-as-co2-levels-rise-16094
[3] http://www.sciencemag.org/content/290/5490/291
[4] http://cdiac.ornl.gov/trends/co2/ice_core_co2.html
[5] http://www.eia.gov/totalenergy/data/annual/index.cfm
[6] http://www.skepticalscience.com/graphics.php?g=12
[7] http://journals.ametsoc.org/doi/pdf/10.1175/1520-0442%282000%29013%3C0617%3AASIVIT%3E2.0.CO%3B2
[8] http://occri.net/climate-science/climate-modeling/sources-of-uncertainty
[9] http://www.sciencedaily.com/releases/2014/03/140327111724.htm
[10] http://www.sciencemag.org/content/312/5780/1612
[11] http://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law#Thermodynamic_derivation
[12] http://geotest.tamu.edu/userfiles/216/dessler09.pdf
[13]http://www.sciencemag.org/content/305/5682/367.short

Wishful thinking

My cousin graduated from medical school about 2 weeks ago. The whole family was here.

Kept asking me when my turn would be.

Years, I said. Years and years.

la foto

Puerto Rico! (part 2)

[for Part I]

When we packed our tent the next morning the sky was just beginning to brighten. It was the start of our first full day in Puerto Rico. The day was cloudy, and wet, but warm. Around our campsite the night rain had made a mat of leaves. There was no time for breakfast. As we hiked out of the forest, pots and pans clanging, our clothes clung to our skin, leaves stuck to our shoes. Humidity gave the impression of sweating profusely.

It had been my idea to camp. I figured between showers at campsites, the occasional dip in the ocean, and one or two hotel stays thrown in, we’d have our hygiene taken care of; and a single trip to the grocery store had already yielded more food than we could eat before it’d all go bad. The $40 emergency Target tent was the shakiest leg of this plan, but even it only had to hold up for a week.

A week. Queenie, a journalist at a newspaper, had about a week’s vacation a year, had never done this sort of thing before, and had to put in for the vacation days about 9 months in advance. But she was excited for the adventure, she said. I guaranteed she’d have a good time. Not to worry, I told her, I’m in charge of the planning. I really wanted her to have a good time.

But even for me, and I’m used to doing this sort of thing, this trip got off to a rocky start.

1398215_680245695201_1314102018_o

My flight was delayed, two hours only, but just long enough to miss the DRNA office hours in San Juan where, with the help of my broken Spanish, we might have gotten a camping permit for the first night. And then, at the baggage carousel, while I watched the luggage go round and round, I realized I had left my tent– a fancy, 2-person ultra-light style REI thing that I had borrowed from my boyfriend– leaning against my bathroom door at home, in Massachusetts.

“We have to buy a tent,” I said, when I spotted Queenie.
“Whaaa…”
“Sorry,” I said. “I think we can get it when we go get the fuel for the stove.”

So, then began the errands. It was rush hour. There was crushing gridlock traffic, cars darting every which way, cars that looked like they’d just as easily drive right over you–through you.

After sitting through the third green light, not moving, watching patiently as each tiny space that was created instantly filled with some car turning, some car backing up, some car running a light cause who cares, some car jumping the curb to get out from behind you, etc, I turned to Queenie. “Dude,” I said. “Go.”

She shook her head.
“This is not how people drive in Oregon.”

It poured as I ran from one store to the next. It was nearly 8 when we finally left San Juan. I put us on the route to Rio Abajo State Forest, chosen for proximity to Arecibo, our next morning’s destination.

After seven or eight miles climbing this overgrown, winding forest road, we came to a dead-end. Our high-beams were the only source of light. We struggled to use it to survey the scene. A mossy sign marked the state forest, mentioned something about el area de acampar; a chain-linked fence rose out of the dirt and leaves; a gate: locked. We debated what to do. It was almost 10, this road was almost abandoned. We would have to hop the fence, leave the car outside, and we would certainly be alone. The sound of Coqui frogs filled the air, and some species of super-loud crickets.

Way too sketchy, we decided. We would try another state forest. With much labor, we turned the car around, drove seven miles back down the same road we came up.

From an online search, it seemed that at our next destination, at the Bosque Estatal de Guajataca, we would need to hike to our camping area. I looked online for a map of trails. Turns out in general Puerto Rican forests and parks don’t do that sort of thing. I found instead one hiker’s homemade map that he’d drawn up of the area. Afraid of losing reception, I decided to keep that page open on my phone.

This state forest looked more promising almost right away. There were signs announcing its existence ahead, mile markers along the well-paved road, which was wide enough for opposing traffic to pass comfortably by. We found the ranger station lit with a single street lamp, unguarded but for a large, angry dog. There was parking space enough for 10 or 12 cars, though we were the only. We were relieved at the prospect of not having to sleep in the car; still, we estimated we probably had until just after daybreak the next morning to get the hell out of there before we would have to answer questions about camping permits.

Quickly, we packed our bags, I brought our dinner and cooking utensils, our tent, a rain tarp. Queenie brought all of her clothes for the whole trip (“Why is your bag so heavy?” I’d ask later). I turned on my phone to check the map. The website refreshed. No internet connection, the blank page said.

I have an obsessive habit now of taking screenshots of important websites and emails, in case of reception loss. Even if there’s no suspicion of reception loss, even if I have every reason to believe a page to stay open. This particular paranoia, I trace back to this exact moment.

“My page refreshed,” I muttered. “Why did my page refresh?”

I tried desperately to get it back. I hit the back button: another refresh. I tried another tab: another refresh.

“I had it open, what, why would this happen? What is the use of this function?”

I didn’t remember exactly when I had lost signal, but it must have been at least 45 minutes out. I tried to picture the map in my head. There was a watch tower. A trail that went past it. The campsite wasn’t too far in. There were only two or three trails in the park, and they looped back on themselves no more than half a mile in. You couldn’t get lost in this. It can’t take more than 30 minutes to walk the whole thing.

Our headlights illuminated a rocky dirt path that was decently well-tended. But the rocks were wet with perennial rain and slippery with moss. The going was slow, the network felt complicated in the dark, I started to lose confidence.

“I think we’ve gone too far,” I said. “It definitely wasn’t this far.”

I started looking for clearings besides the trail, where we might be able to just pitch our tent. That’s when we walked by the tower.

It was a wooden structure about 20 feet tall. Two or three flights of steps led up to the top platform, which was wide enough for a place to sleep and a place to cook. A tilted roof sheltered the whole thing from weather. Looking out I could see the dark outlines of hills in the distance. I noticed the stars for the first time that night, how slightly shifted they were from where they’d been back home, and that little difference was enough to make them nearly unrecognizable. OK, we can sleep here, I thought, like two homeless people. I was a little sad.

Then my phone buzzed in my pocket, an email alert. That little height was all it took and I had reception.

For birds without wings

On war:

Where does it all begin? History has no beginnings, for everything that happens becomes the cause or pretext for what occurs afterwards, and this chain of cause and pretext stretches back to the paleolithic age, when the first Cain of one tribe murdered the first Abel of another. All war is fratricide, and there is therefore an infinite chain of blame that winds its circuitous route back and forth across the path and under the feet of every people and every nation, so that a people who are the victims of one time become the victimisers a generation later…
[pg. 257]

I picked it up at a used book store in Harvard Square while delivering a box of used books to sell. Knowing very little about the history of the Ottoman Empire, I expected at least to be educated. Historical fiction, incidentally, not something I read a whole lot of.

I found out: this is an incredibly sad book.

Reading this book is like wading into a lake of sadness. Sadness of people who aren’t real but are. Towns that aren’t real but are. How else could you teach about the toll of nation-building? This is an immersion up to the chest in tragedy: of an individual sort, of a community, and of a nation.

On war:

Personally, I liked the idea of a new Greater Greece, in theory, but I couldn’t see the point of risking anything for it, and I couldn’t stop thinking of the mainlanders as at worst a bunch of crazy foreigners, or at best like embarrassing cousins with too many halfwits in the family. I wasn’t in any kind of mood to die for them, and no one was more surprised than me when they decided to come over and die for us. I can’t say I was very surprised, however, when the fiasco concluded with all of us losing everything, and it was we who died for them… Just as we sensible types feared all along, the romantic enthusiasms of people like Leonidas ended up with peaceable fellows like me drowning in harbours while their cities burned.
[pg. 234 Georgio P. Theodorou]

I found out: The Ottoman empire, though on the decline for many years, actual held together until World War I. This was news to me because I know nothing about history of any sort. Sorry.

The Ottoman empire, surprisingly religiously tolerant and pluralistic at the time, was home to Christian Greeks, Armenians, Assyrians, and even Jews. A community might speak Turkish, or Greek, or Armenian. Many citizens spoke more than one language. The literate might write Turkish with Arabic letters, or Greek with Greek letters, or even Turkish with Greek letters. Mosques and churches were erected alongside one another. Worshippers for the most part went about their separate businesses but might occasionally wander into a service outside their faith. Inter-faith marriage was not unknown.

Then, in midst of a revolution of its own, the Ottoman Empire entered World War I on the side of the Germans.

On war:

Your father says that a soldier is like one of the fingers of a potter and his comrades are the other fingers, and the soldiers of the enemy are the fingers of the other hand, and they work in opposition because no pot was ever well made with one hand, and the potter is God, and God moulds the world like clay by means of soldiers, so he says you should be proud to be one of God’s fingers, and if not proud, resigned. Your mother says that it is important to wash your clothes whenever possible or else your skin will become itchy and inflamed. And she says that she wishes you were a child once more and did not have to go off to war.
[pg. 322 Leonidas the teacher]

During the war, atrocities are committed by the Ottomans onto its own Armenian population, under justification of “treachery” on the part of some Armenians. After their defeat, occupied by Allied forces and facing the potential loss of their nation-state, Turks fight for their independence under the leadership of Mustafa Kemal against Greek ambitions for their (historically Greek) land. Greek armed-forces massacre Turkish civilians; then Turkish forces massacre Greek civilians. Christians are deported from the newly created nation of Turkey & muslims from Greece. Mosques and churches left behind are defaced and destroyed. Whole cities go up in flames.

In the book, we wade with our characters ever deeper into the loss and sadness of a-war-they-didn’t-ask-for. The loss of life is both casual and breath-taking. The loss of a beautiful town is both slow and sudden.

For birds with wings nothing changes; they fly where they will and they know nothing about borders and their quarrels are very small.

But we are always confined to earth, no matter how much we climb to the high places and flap our arms. Because we cannot fly, we are condemned to do things that do not agree with us. Because we have no wings we are pushed into struggles and abominations that we did not seek, and then, after all that, the years go by, the mountains are levelled, the valleys rise, the rivers are blocked by sand and the cliffs fall into the sea.
[Epilogue]

Puerto Rico! (with pictures) — Part 1

First night, weaving through dense forest on a one-lane two-way road, looking for a place to sleep, the transmission light turns on. Queenie, at the wheel, reads aloud the service message.

“God, we just got this car today,” she said.

And this is what our trip would be: learning to live with, to adapt to, & to love, even, dysfunction.

puerto rico 272

I left Boston in the pre-dawn hours. It was just above freezing as I stood in the wide, quiet, South End street waving at taxis. Now, that same night, I found myself paused under a canopy of huge and dripping leaves, pounds of clothes lighter, not yet with any sleeping arrangement, contemplating a two-headed dog blocking the road. A minute ago, Queenie had been concerned about the intermittent snapping noise that came from the rear left side of the car. I had been “pretty sure” we were going the right way.

And we’d come to a sudden stop. There was a kind of surprised silence, but only for a second, as if the whine of the engine, the spatter of tires on gravel, the chatter in the front seats gone, had left a void which the forest considered, then gladly filled with its own sounds.

“Drive up a bit,” I said.

We had two big overnight packs stuffed with clothes, water, a first-aid kit, and ingredients for making pasta; we had my new camping stove after I abandoned plans to buy fuel for the stove I’d brought; we had a $40 caseta freshly procured from the Kmart in San Juan (I’m sorry! I just forgot it!), and a half-hatched plan for the first night to camp in a state forest near Arecibo.

Closing in, we discovered the two-headed dog was two dogs seemingly attached at the hip. Lit by our high-beams, the dogs tried to bolt in opposite ways, were then snapped back by whatever was holding them together. Finally, one won over the other, and they hobbled, half tumbled, off the road.

“We’re all adults here,” Ernesto the biologist would lead with a few days later, in the cave, in awkward explanation of this strange encounter. But in the dense wet night, vines brushing the windshield of our car as we drove ever deeper into a strange forest on a strange island, it seemed that anything was possible. Turning around at the locked gate at the end of the road (we wouldn’t be camping there that night), though there was no other way to go but back, there was still some hesitation.

“Do you think it’s still there?” Queenie asked.

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