Infinite Fetch and the Blooming Phytoplanktons

The disappearance of Malaysian Airlines Flight 370 is deeply unsettling to me. Not only is it a tragedy of loss and uncertainty for the friends and families of those on board, but it's also a disconcerting reminder of how very big the Earth is.

The search for the flight has mainly focused over the South Indian Ocean, where it's been stymied by treacherous weather and unpredictable currents that could take debris in any direction. It's a part of the world that we rarely think about, but the recent search efforts have been a reminder to me that it's actually tremendously important.

The South Indian Ocean is part of what climate scientists think of as the "Southern Ocean"--a vast stretch of the world's water that wraps all the way around Antarctica without any land to get in its way.

One side effect of the absence of land, is "infinite fetch."

Aside from being the name of my future rock band and an excellent compliment on someone's looks, "infinite fetch" refers to the fact that, because there's no land in the way, the winds above the Southern Ocean have a fetch (what oceanographers call the distance over which winds blow in a roughly constant direction) that's essentially an infinite loop. The longer the fetch, the bigger the waves and the stronger the storms. Hence, the unpleasant MH370 search conditions.

Image courtesy of William Putnam and Arlindo da Silva, NASA/Goddard Space Flight Center.
A model simulation shows the flow of particle air pollution over the Southern Ocean.

On Tuesday, though, I was reminded of another way in which the Southern Ocean is a climate science box of chocolates. Dr. Daniel Sigman, Princeton Geosciences Professor and winner of a 2009 MacArthur "genius" grant, led a dinner discussion featuring some of his lab's work that was recently published in Science magazine.

The work confirms a fascinating feedback loop that is thought to have helped the last ice age take hold.

The Southern Ocean is full of phytoplankton, little ocean organisms that (among other things) turn carbon dioxide into oxygen. The phytoplankton need iron in order to grow, which there's relatively little of in the Southern Ocean, though there are tons of the other nutrients phytoplankton need. If lots of iron were to miraculously appear, the phytoplankton could grow rapidly and turn more carbon dioxide into oxygen.

Here's the feedback loop that Dr. Sigman's lab has confirmed:
Step 1: Cooling from the start of the ice age dried out the southern continents, leading to more dust.
Step 2: That dust, which was filled with iron from the soil, blew over the Southern Ocean and settled on it.
Step 3: The extra iron in all that dust led to a big bloom in phytoplankton growth.
Step 4: As the phytoplankton grew, they turned huge amounts of carbon dioxide into oxygen.
Step 5: Because carbon dioxide is a greenhouse gas, less of it meant that the planet got cooler.
Step 6: That cooling led to more drying in the southern continents, and we're back to Step 1!

In the image above, from a model simulation of modern-day atmospheric pollution flows around Antarctica, you can see big plumes of dust (the red/orange stuff) coming off of South America. Imagine this multiplied several times over and you get an idea of what was going on during the ice age.

The theory Sigman's group confirmed was first theorized in the early 1990s, and has spawned lots of speculation about how deliberate iron fertilization could be used to engineer storage of carbon dioxide in the ocean. Even though I'm not an oceanographer, "geoengineering"schemes like iron fertilization open up a whole vat of interesting (and troubling) environmental policy questions, so I dug into the topic a bit for a class a few semesters back.

Iron fertilization is controversial, and possibly dangerous and ineffective. In order for the carbon dioxide to actually get stored, the phytoplankton have to sink below the mixed layer of water at the surface when they die, which only happens 10% of the time. The phytoplankton blooms can also be toxic and cause changes farther up the food chain. Then there's all the carbon dioxide that would be emitted in mining the iron and getting it out to where the phytoplankton are (check out this report for more).

Nonetheless, a random Californian businessman, Russ George, apparently tried doing it single-handedly off the coast of Alaska in 2012, which raises lots of interesting governance questions. How should we approach deliberate ecological manipulation? How do we monitor attempted iron fertilization (George's fertilization scheme was only identified in satellite imagery after he announced its completion)? And should we even consider trying to solve one environmental problem by potentially creating another?

The Earth is so very big, and I have so many questions.

Not all uncertainty is created equal.

Highway 280 between San Francisco and Palo Alto is an Earth Scientist commuter's dream. The wide stretch of road bends along the San Andreas Fault (the Pacific tectonic plate out one window, the North American plate out the other), and a sunset driver can watch the marine stratus clouds spilling over the Santa Cruz Mountains like melting whipped cream.

This week, I'm out in California, visiting collaborators at the Carnegie Institution at Stanford and enjoying my twice-daily Hwy 280 meditation. My visit happens to overlap with that of Dr. Kerry Emanuel, a brilliant and eloquent climate scientist from MIT, who specializes in interactions between hurricanes and climate (he recently did an interesting Reddit Ask Me Anything). 

Dr. Emanuel is a co-author of a new climate science report, What We Know, that's been getting lots of press in the last few days. The report and the broader initiative that it's part of are a push to communicate the scientific realities and risks of climate change, as well as potential societal responses, by the American Association for the Advancement of Science (the organization in charge of Science magazine).

On Tuesday, a New York Times article on the report highlighted an aspect of climate science that I mull over frequently: the uncertainty associated with climate change. 

We know lots about the basics of climate science—that more human-produced carbon dioxide is increasing global temperatures and that increased global temperatures have a lot of problematic implications for delicate environmental systems—but there are lots of uncertainty bars on the things that we can predict. For example, we know that the climate warms when there's more carbon dioxide, but we don't know if the climate will get 1°C warmer or 6°C warmer if we double the amount of carbon dioxide in the atmosphere (though we do have an idea of what the relative probabilities of different values in that range are). 

But what does that uncertainty mean for taking (or not taking) action to reduce climate change?

Well, that depends on what type of uncertainty you're talking about. Uncertainty in the climate system comes in all shapes and sizes and the different types may mean different things for policy.

Let's say you're trying to buy a house. Before you make the decision of which house to buy, you probably want to take into account what its resale value is likely to be, say, 20 years down the road when you might want to move. When you look at a house, the possible resale value is pretty uncertain. Some parts of that obviously can be reduced: you can get a home inspection, you can research the property values of other houses in the neighborhood, etc. But other parts can't be reduced: you can't predict if the housing market is going to crash somewhere in the next 20 years. 

You'd be insane to buy a house without doing things like a home inspection, but it's completely unfeasible to wait to buy a house until you know what the housing market will be like in 20 years.

Uncertainty in climate science comes in those two flavors as well. You have reducible uncertainty (uncertainty that comes from things that we don't yet understand about the climate system), but you also have irreducible uncertainty (uncertainty that comes from natural variability in the inherently chaotic climate system and from the unpredictability of what technology choices society will make). 

Forty years ago, one could certainly have made an argument that we needed to know more about the climate system before policy action on climate change would be rational. But the irreducible forms of uncertainty are rapidly overtaking the reducible forms of uncertainty as we make progress in climate science. 

(Climate scientists actually think a lot about how to quantify the relative contribution to predictions from these two types of uncertainty—too much for me to attempt to summarize here. For people who want to do more digging, the most broadly cited of these studies is probably this 2009 paper, which is actually very readable, even for people outside of climate science. Or you can read the overview of that paper from the awesome climate science blog, RealClimate.org, run by a whole bunch of highly respected climate scientists.)  

The New York Times article I mentioned before makes this point:

"The issue of how much to spend on lowering greenhouse gases is, in essence, a question about how much insurance we want to buy against worst-case outcomes. Scientists cannot decide that for us."

The fact of the matter is that there will always be uncertainty surrounding climate change, how bad it will be, and what its impacts will look like. 

Some of that is reducible—it will decrease as we learn more and more about the climate system. But some of it is irreducible—our climate system is an inherently chaotic one and there are limitations on what can be predicted, even with perfect knowledge. 

The question then becomes, how much insurance are you willing to buy?

What's your question?

Great conversations can be had over tea. My roommate and I will often find ourselves gravitating toward the kitchen in the late evening, orbiting the tea kettle until it whistles and enjoying the brief distance from our work.

During a recent nighttime tea break, my roommate (who is a masters student in public policy) admitted to a fascination with PhD students--what do we spend our time doing, and how do we know what to do on any given day?! My off-the-cuff answer surprised me: "well," I said, "we spend most of our time trying to figure out what questions to ask."

The scientific method--as laid out by that most reliable of sources, Wikipedia--starts with defining a question (e.g. Why did the chicken cross the road?).

Once you have a question, you:
-do some information gathering on your question (What was on either side of the road? What might be some primary motivators for a chicken? What are some existing hypotheses for why the chicken crossed the road?)
-come up with a hypothesis (The chicken crossed the road to get to the other side)
-design and perform a test for your hypothesis (I welcome suggestions for how to test this hypothesis)
-analyze the results of your test
-draw some conclusions about whether or not your hypothesis was right
-rinse and repeat from the hypothesis formation point until you have a correct hypothesis
-and, finally, publish your results.

We all learned the scientific method in elementary school, right? But what I've only recently realized is that step one, defining the question, is actually the hardest part.

Defining your question is only the first step in the multiple step scientific process, the end result of which (publishing your results) is what ultimately gets you hired in an academic job or gets you tenure (though there's an interesting ongoing debate on whether this is the best mode of evaluation). With the time pressure of trying to finish a PhD or beat the tenure clock, it can be so tempting to rev through that first step so that you can get moving on the rest of the process.

Defining a good question is hard. It requires reading lots of journal articles--the result of other people successfully getting all the way through the scientific process--so that you know what questions have already been asked. (And, let me be honest, trying to read scientific journal articles sometimes makes my brain feel like swiss cheese.) It requires going to scientific seminars to figure out where the interesting questions in your field may lie (and not spending them making to do lists instead of listening intently). Defining a question requires much more mental energy and focus for me than sitting down to write a piece of code. But without a fully baked research question, you can end up wasting a lot of time.

My seemingly glib response to my roommate has reasserted itself several times this week. On Monday, I met with some collaborators to figure out how to set up some model runs we want to do. We'd been going back and forth and confusing ourselves about how to structure things for about two weeks. In the end, it all came down to the fact that we hadn't thought thoroughly enough about what question we were trying to ask. On Tuesday, I had a meeting to pitch an idea for a policy paper--a pitch that I don't think ended up being very successful, partly because I didn't properly articulate the question I thought it would answer. On Thursday, I met with a professor about a possible final project idea for a class. That meeting went very well, largely because the whole project was inspired by a singular question that I wanted to figure out the answer to.

I'm a naturally impatient person; delayed gratification is not my strong suit. But the virtues of a well-defined, interesting research question may be enough to overcome even my flighty disposition. I resolve to spend more time figuring out what questions to ask. Perhaps if that were a more universal resolution, we could have been spared ever being asked the question: why did the chicken cross the road?

Communication is a two way street.

I often listen to my hometown NPR station's online audio stream in the morning. It fuels a constant low-level nostalgia for my childhood, and gives me a heads up on the ice storm or traffic jam that my mom will likely be calling me about later in the day.

This Tuesday's NPR Morning Edition featured an interesting case study in science communication that got me thinking about how much the impact of my scientific research depends on the time and energy that I'm willing to spend communicating it to others.

The NPR piece profiled some recent work by Brendan Nyhan, a political scientist at Dartmouth, and others that looks at how parents process medical information on the safety of vaccinations. They found that parents who were originally least likely to vaccinate their kids will think that the vaccine is safer after being given correct medical information, but will then report being even less likely to vaccinate their kids. The basic scenario that Nyhan seems to be proposing is this:

Step 1: Person is confronted with information that runs counter to what they've previously thought
Step 2: Person contemplates the possibility that the new information might be true
Step 3: Person's sense of identity and intelligence is threatened by the new information
Step 4: Person tries to find ways to prove new information wrong in order to preserve their ego
Step 5: Person consequently does the exact opposite of what you were hoping for when you gave them the new information

Not encouraging!

Even though the piece was about public health, it gets to the heart of a question that I struggle with constantly as a climate scientist: What is my responsibility to communicate my work outside of the scientific community, and how do I do that effectively? 

Climate scientists especially run the risk of telling people things that they don't want to hear, and Nyhan's work suggests that this can end up doing more harm than good, if you're not careful. Is the solution, then, not to communicate at all? But isn't that even less helpful and maybe even negligent?

Luckily, Wednesday afternoon gave me another chance to contemplate the issue. Three leading Princeton thinkers, Michael Oppenheimer, Melissa Lane, and Robert Keohane, were giving a lunchtime seminar on the Ethics of Scientific Communication. If there's one thing that graduate students universally love, it's a free lunch, so I was looking forward to both the intellectual and the physical nourishment.

Some of what O, L, and K said seemed like common sense (you can find a reference to the paper they've written on the topic here, as well as info on their research program on communicating uncertainty in climate science), but one aspect in particular stood out for me. Melissa Lane pointed out something that I suppose marriage counselors have known for ages: communication is a two way street--it's about the person communicating the information, but it's also about the person receiving it. In their talk, this came up mostly in terms of the communicator's responsibility to know her audience.  But this raises an important question--What is the audience's responsibility in scientific communication?

If communication is a two way street, and the communicator has certain responsibilities to uphold, does the receiver have responsibilities as well? O, L, and K suggested five core principles that scientific communicators need to take into account in order to responsibly communicate their work: honesty, precision, audience relevance, process transparency, and specification of uncertainty. But what about the audience? Do they have a responsibility to make a good faith effort to put their prejudices aside when evaluating new scientific information? Does the burden of solving the problem that Brendan Nyhan raised lie with the communicator or with the receiver? What about society as a whole? Does society have a responsibility to prepare its citizens with a minimum level of scientific literacy, so that they can make use of important scientific findings?

I certainly think that scientists can do much, much more to train themselves to communicate effectively, but maybe there's some way to meet in the middle.

I suppose I'm left with more questions than answers. Though, half of being a graduate student is figuring out what questions to ask, so maybe that's not necessarily a bad thing (more on that next week). In the meantime, I should call my mom.

Phenomenal Things, Basically.

On a recent trip home, I was undertaking that favorite past-time of twenty-something year olds--cleaning out my childhood bedroom. In a repurposed VHS case labeled 'My Treasures', I discovered an unmarked cassette tape that turned out to hold,
"The biography of Geeta Gayatri Persad from date of birth to age ten and three quarters."

I listened through it in a haze of nostalgia--young me clearly had a cold when she recorded it, and the recording is scratchy and fuzzy with time--but one section keeps returning to me at unexpected moments. Ten and three quarter year old me is describing a field trip to the McDonald Observatory in Fort Davis, Texas and begins waxing poetical:

"I want to be an astronomer when I grow up, an environmentalist, or somebody who--who studies, um, weather patterns--well, how they affect the earth--and outer space...Sigh...Phenomenal things, basically."

I am often asked (and, to be honest, often ask myself) why I chose to get my PhD in Climate Science. I'm in the third year of my doctorate in the Program in Atmospheric and Oceanic Sciences at Princeton University, studying how liquid and solid particles that come from burning stuff (also known as aerosols) affect our climate system when they get into the atmosphere. My interests have ranged far and wide, from Shakespearean theater to existentialist philosophy to classical dance, but ultimately I suppose I've decided to dedicate these years to a PhD because I want to study phenomenal things, basically. How does the Earth maintain itself? And what is humankind's fundamental relationship to that maintenance? These are questions that sound almost philosophical, but are also (I think) the core questions to which all questions in Earth and Environmental Science lead. Thinking about them gives me an almost transcendental feeling, and if that's what being a nerd means, then I will gladly accept the title.

This blog will be my attempt to convey my search for phenomenal things to all of my friends and family who wonder what a climate scientist in training does with her time. I'll post thoughts and questions on the fascinating seminars from all over campus that punctuate my day, I'll share the articles and news pieces that climate scientists are chatting about over the proverbial water cooler, and who knows what else.

Read, comment, question, and join me as I let down my hair and try to share what getting a PhD in Climate Science is really all about.