Climate Change And The Astrobiology Of The Anthropocene

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The Geologic History of Earth. Note the timescales. We are currently in the Holocene, which has been warm and moist and a great time to grow human civilization. But the activity of civilization is now pushing the planet into a new epoch which scientists call the Anthropocene.

You can't solve a problem until you understand it. When it comes to climate change, on a fundamental level we don't really understand the problem.

For some time now, I've been writing about the need to broaden our thinking about climate. That includes our role in changing it — and the profound challenges those changes pose to our rightly cherished "project" of civilization.

Today, I want to sharpen the point.

But first, as always, let's be clear: We have not gotten the science wrong. The Earth's climate is changing because of human activity. That part has been well-established for awhile now, in spite of the never ending — and always depressing — faux "climate debate" we get in politics.

But the part of climate change we've failed to culturally metabolize is the meaning of what's happening to us and the planet.

In other words, what we don't get is the true planetary context of the planetary transformation human civilization is driving. Getting this context right is, I think, essential — and I'm dedicating most of the year to writing a book on the subject. The book's focus is what I believe should be a new scientific (and philosophical) enterprise: the astrobiology of the Anthropocene.

I meet a lot of folks who've heard of both astrobiology and the Anthropocene before. In general, however, lots of people look at me a bit sideways when I use either word, much less lump them together as the future of humanity.

Given that experience, let's start with a couple of definitions.

A trip to NASA's astrobiology homepage will tell you the field is all about understanding life in its planetary context. It might seem strange to have an entire scientific domain dedicated to a subject for which we have just one example (i.e. life on Earth). But take that perspective and you'd miss the spectacular transformation astrobiology has brought to our understanding of life and its possibilities in the universe.

All those planets we've discovered orbiting other stars are part of astrobiological studies. The robot rovers rolling around Mars proving that the planet was once warm and wet — they are astrobiology, too. The same is true for work on Earth's deep history. These studies show us that Earth has been many planets in its past: a potential water world before major continents grew; a totally glaciated snowball world; a hothouse jungle planet. In understanding these transformations, we've gotten to see one example of life and a planet co-evolving over billions of years.

If you want an example, consider how cyanobacteria, or blue-green algae, completely reworked the planet's atmosphere 2.5 billion years ago giving us the oxygen-rich air we breathe today. Another example is the work showing how after the retreat of Ice Age glaciers, Earth entered a warm, wet and climatically stable period that geologists call the Holocene — about 10,000 years ago.

The Holocene has been a good time for human civilization to emerge and thrive. The seasons have been pretty regular, moving between relatively mild boundaries of hot-ish and cold-ish. That transition was the key change and allowed humans to get stable and productive agriculture started.

But, thanks to civilization, the Holocene is now at an end. That's where the story gets really interesting and where the Anthropocene makes its entrance.

Scientists now recognize that our impact on Earth has become so significant we've pushed it out of the Holocene into the Anthropocene, an entirely new geological epoch dominated by our own activity (see Andy Revkin's reporting on the subject). And it's not just about climate change. Human beings have now "colonized" more than 50 percent of the planet's surface. And we drive flows of key planetary substances, like potassium, far above the "natural" levels.

It may seem impossible to some folks that a bunch of hairless "primates" could change an entire planet. But that view misses the most important part of our story, the part that speaks directly to our moment in planetary evolution.

What I'm interested in, now, is putting these two ideas together: the astrobiology of the Anthropocene. That means looking at what's happening to us today from the broadest possible perspective. A couple of years ago, my colleague Woody Sullivan and I published a paper titled "Sustainability and the Astrobiological Perspective: Framing Human Futures in a Planetary Context." The idea was to show how much of what's been learned in astrobiology could be brought to bear in understanding what's happening to us now (a'la climate change, etc.). Going further, we wanted to know how the astrobiological perspective about life and planets might also help us understand what to do next. (Here is a piece I wrote for The New York Times about it, since the paper is behind a pay wall.)

Our robotic probes of Venus and Mars provide one good example of this intersection. Both planets have taught us about climate extremes. Venus is a runaway greenhouse world and Mars is freezing desert. Venus taught us a huge amount about the greenhouse effect. Even better, we have ample evidence that Mars was once a warm, wet and potentially habitable world. That means Mars provides us a laboratory for how planetary climate conditions can change.

So why does that matter so much?

Astrobiology is fundamentally a study of planets and their "habitability" for life. But sustainability is really just a concern over the habitability of one planet (Earth) for a certain kind of species (homo sapiens) with a certain kind of organization (modern civilization). That means our urgent questions about sustainability are a subset of questions about habitability. The key point, here, is the planets in our own solar system, like Mars, show us that habitability is not forever. It will likely be a moving target over time. The same idea is likely true for sustainability — and we are going to need a plan for that.

Woody and I are not the only ones thinking about astrobiology and the Anthropocene. David Grinspoon, a highly-respected planetary scientist has also been pursuing his own line of inquiry on the issue. As the Library of Congress's chair of astrobiology, Grinspoon began exploring his questions with experts in fields as diverse as history and ecology. His new book The Earth In Our Hands gives a beautiful and detailed overview of the ways we must change our thinking if we want to truly understand the transformation in our midst.

Thinking about the astrobiology of the Anthropocene in terms of just our species is, I think, a rich line of inquiry. But I think we can go even further. In the last part of my book I'm following a line of research that is also the focus on my sabbatical year.

As a theoretical physicist, I'm used to watching colleagues take the science we understand now and extend it to new possible domains of behavior. This is what happens when particle physicists think about new, but as yet unobserved, kinds of particles. Such theoretical investigations can prove enormously beneficial in widening our vision of the world's behavior.

There is no reason we can't take the same approach with the astrobiology of the Anthropocene. Earlier this year, Woody and I used the amazing exo-planet data (and some very simple reasoning) to set an empirical limit on the probability that we are the only time in cosmic history that an advanced civilization evolved. It turns out the probability is pretty low — one in 10 billion trillion. In other words, one can argue that the odds are very good that we're not the first time this — meaning an energy intensive civilization — has occurred. With that idea in hand, you can take a theoretical jump and ask a simple question: How likely is it that other young civilizations like our own have run into the kind of sustainability crisis we face today?

We know enough about planets and climate to begin investigating that question. In our 2014 paper, Woody and I presented an outline for this kind approach. One can ignore science fiction issues about alien sociology and just ask physics — i.e. thermodynamic — kinds of questions.

If young civilizations use some particular energy modality (combustion, wind, solar, etc.) what will the feedback on their planet look like? (By the way, as we've discussed before, there is always a planetary feedback when using lots of energy for large-scale civilization building. No free lunches folks. Sorry).

Woody and I sketched out the kind of behaviors you might expect from this kind of modeling. Considering just population, energy use and planetary feedback, one can imagine models showing trajectories of history that lead to collapse or to sustainability.

Which path a civilization finds itself on will depend on the parameters for their planet and the energy modalities (sources) they're using (or switching between). Of course, the models I am building are not reality. But they can prove to be a huge help in understanding the interplay of forces that shape the fate of planetary-scale civilizations like ours. In the end, this kind of understanding can help us at least understand what we're up against. Are we doomed, or is there a lot wiggle room in the choices we have to make?

The key point, for me, is that consideration of the astrobiology of the Anthropocene changes the frame of our debate and lets us see something we have been missing. We're not a plague on the planet. Instead, we are simply another thing the Earth has done in its long history. We're an "expression of the planet," as Kim Stanley Robinson puts it. It's also quite possible that we are not the first civilization is cosmic history to go through something like this. From that perspective, climate change and the sustainability crises may best be seen as our "final exam" (as Raymond PierreHumbert calls it). Better yet, it's our coming of age as a true planetary species.

We will either make it across to the other side with the maturity to "think like a planet" or the planet will just move on without us. That, I believe, is the real meaning of what's happening to us now. It's a perspective we can't afford to miss.

Adam Frank is a co-founder of the 13.7 blog, an astrophysics professor at the University of Rochester, a book author and a self-described "evangelist of science." You can keep up with more of what Adam is thinking on Facebook and Twitter: @adamfrank4

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