Earth in Human Hands

by David Grinspoon

  However you come down on extinction, if you regard mass human starvation as a tragedy, an ice age would be bad news indeed. It’s not the biosphere that is fragile, it’s our civilization. We’ve inhabited all the coastal regions and become dependent upon agricultural activities that span the globe. In our ten-thousand-year run we’ve come to depend on a climate stability that will not last.

  So, then, isn’t it a good thing if we’ve eliminated the threat of ice ages for the next several million years? Well, it might be, but there’s a hitch. Unfortunately, what Jacob’s results actually show is that Earth can be expected to be stabilized for all this time in an ice-free state. We’ve not only stopped the climate pendulum from swinging, but we’ve also got it pinned at one extreme end of its range. An ice-free Earth may in itself not sound horrible, unless you’re attached to the kind of planet we’ve always known and you are fond of penguins, polar bears, and the countless other species dependent on icy high-latitude environs. Yet we have no idea what this implies for the planet as a whole. How hot will the equatorial regions be in this new normal? What will happen to ocean circulation, sea level, precipitation patterns, and the rest of the biosphere? Nobody knows, but it is clear that this would be a drastically altered Earth.

  Yet, there is a potentially more hopeful aspect to these results. They show that the magnitude of the natural Milanković oscillations is not so large as to be beyond the reach of human tinkering. The amount of forcing that is required to change Earth from ice age to hothouse can be modified even with our current technology, which certainly pales in comparison to the technology of a civilization that has learned to survive for another ten thousand years. So, if and when we develop the capacity to apply our powers with a little more collective will and a lot more finesse, to apply them sensibly in the service of a healthy biosphere and a stable, healthy human civilization, it shouldn’t be that hard to adjust the climate of Earth to a desired state—not hard, at least, from a technical point of view. It wouldn’t be like trying to move Earth in its orbit or change the brightness of the Sun, projects that are perhaps not physically impossible but are completely unimaginable for us. By contrast, Earth’s greenhouse climate balance is clearly malleable. Obviously in the near term we quickly need to limit our CO2 emissions and reduce our impact on the climate. We don’t want to try to live on the perpetually ice-free Earth that would result from our present course. In the longer run, though, if we make it that far, we will likely choose not to take our hands completely off the scale. We would want to dampen these severe natural oscillations, not by pinning the system at either extreme end of its natural range. We’d want to choose a more moderate climate, something like the one we have become accustomed to.

  Is it possible that the most recent ice age may be the last one ever? Given the scale of inadvertent human climate interference, and the potential scale of thoughtful human climate intervention, and given at least the possibility of our long-term habitation on Earth, I’m going to say yes, this is quite possible. With us here, Earth may have no more glacial cycle. Would that be a bad thing? I’m going to vote no. No more glaciers? That would be bad. No more ice ages? Good riddance.

  Ultimately, the only way we could have such a prolonged and moderating effect is if we became a much more mature, thoughtful presence on this planet. If we simply use up our fossil fuels in an orgy of consumption, then our influence on the atmosphere will be catastrophic but geologically short-lived. After a few million years at the very most, the Milanković climate rhythms would resume their complex beat. The only way our influence could produce a more sustained interruption, sparing the planet the horror of future ice ages, is if we planned it that way. We would have to become something new, and fully make the transition to the kind of species that enacts planetary changes of the fourth kind. Our current planetary changes of the third kind might cause the glacial cycle to skip a few beats at most. If the cycle is shut down, it will be by a species that knows what it is doing and why.

  When it comes to very-long-term climate change, the range of what is natural goes far beyond what we are used to, and extends into some pretty scary territory. Famine and mass death are also natural, but probably not what reflexive nature lovers have in mind. On its own, Earth is capricious and cruel. If we want to keep our civilization for long enough, we’re going to have to deal with that. On the longer timescales of the ice ages, in order to prevent these deathly oscillations, we will have to learn to provide negative feedback that is missing from the natural Earth system.

  Planetary Engineering

  If we can talk about applying smart engineering to moderate the glacial cycle in the distant future, why not use it right now to deal with our much more urgent problem of anthropogenic global warming? Do we really need to give up our precious fossil fuels, or can we come up with some clever new way to interfere in the Earth system to counteract their undesirable side effects? Can we invent our way out of this problem, substituting innovation for self-restraint?

  Thus we come to the thorny subject of Earth climate intervention, or “geoengineering,” the idea that we could undertake purposeful climate manipulation to fix some of the problems we’ve inadvertently created. It may seem like I’m coming into this topic ass backward, introducing the contentious subject of present-day climate engineering after the more abstract topic of far-future climate meddling. Yet this is how I first learned about the subject: as a subset of the larger, more general problem of planetary engineering.

  Despite the rush of recent attention, it’s not a new idea. For a long time, planetary scientists and science-fiction writers have been exploring the problem of how to purposefully interfere in climate. In the years during which they were doing their fundamental studies comparing climates on Venus, Earth, and Mars, Carl Sagan and Jim Pollack also studied the problem of terraforming. This is the idea that someday we might be able to change the environment of another planet to be more Earth-like, turning it into a friendly place for terrestrial life. As a part of their wider study of climate manipulation they also looked into what is now called geoengineering.

  When I was at NASA Ames Research Center as a postdoc working with Pollack, he and Sagan were working on a paper entitled “Planetary Engineering” for an upcoming book, Resources of Near-Earth Space, edited by my PhD adviser, John Lewis. Lewis was a hands-on editor who had a lot of input into their chapter.* Since my three main scientific mentors were all collaborating on a project about purposeful engineering of climates around the solar system, I heard a lot about this topic.

  The idea of finding Earth-like havens elsewhere in the universe is an old one. In the 1600s, after we figured out that the planets were other worlds but still knew nothing of their environments, many scientists imagined them as essentially other Earths, inhabited by familiar kinds of life. Then, once we started to learn, first with telescopes and then with spacecraft, how alien those other planets actually are, people started wondering if we might someday remake them more in Earth’s image. What if at some point we wanted to change a planet such as Mars or Venus into a place where Earth life could thrive? How would we do it? Could we? Should we? Many scientists have seriously studied the problem for decades, with increasing sophistication as we’ve gathered data on the other planets and learned how climates can change.

  Terraforming has been the subject of several technical workshops and has generated a sizable literature of peer-reviewed papers. Since we’ve become aware that we are now inadvertently “Veneraforming” Earth (slowly making it more Venus-like), these models have new relevancy. While I was at Ames another group of planetary climate modelers, including Chris McKay, Brian Toon, and Jim Kasting, was also working on a paper about terraforming Mars, which was published in Nature in 1991. So this community of scientists who had collectively figured out the Venus greenhouse, Martian dust storms, the Titan anti-greenhouse, volcanic climate catastrophes, giant impacts, and nuclear winter was also involved in studying terraforming. It makes sense when you consider how t
hese studies are all connected, variations on the same overlying problem. For scientists interested in how climates can change, and how we might accidentally change a climate, it is irresistible and instructive also to explore how we might purposefully adjust a climate. It’s the same class of problem we solve when we predict long-term climate change on Earth, using the same physics, the same equations and similar models. You ask: How does this climate system function and change? How stable is it against different kinds of perturbations? What would be the best leverage points if we wanted to alter it? Where are the greatest sensitivities and what would be the cheapest way to influence them? How would these changes affect the rest of the system? Would the new state be stable or require continual inputs and meddling? On what timescales?

  Terraforming gives planetary climate modelers additional scenarios to study. It’s also undeniable that most of us space geeks have been influenced in some way by science fiction, most went through at least enough of a phase to gain familiarity with the canon, so we’ve all glimpsed the dream of a multiplanet human future even if some regard it as more of a fairy tale.

  Pollack and Sagan began their planetary engineering paper by mentioning global warming, ozone depletion, and nuclear winter, declaring, “These three processes demonstrate the general proposition that humans can now alter environments on a planetary scale… It seems possible, therefore,” they wrote,

  that within the not too distant future human technology should be capable of even more major alterations… An important issue is whether any can cause improvements rather than deterioration in the planetary environment—perhaps with high-precision negative feedbacks.

  Then they discussed each of the other three worlds of our solar system with solid surfaces and sizable atmospheres—those that could potentially be terraformed: Mars, Titan, and Venus. On Mars and Titan, the challenge would be to enhance the greenhouse effect, causing deliberate global warming, raising the temperature to the point where liquid water would be stable on the surface and plants could grow and begin to work their self-reinforcing magic. Eventually, with large increases in temperature, pressure, and oxygen level, people might someday live on Mars without need of an enclosed habitat or suit. Sagan and Pollack went through the different gases that might be released into the air on these worlds, and thus trigger feedbacks that might push them into warmer states.

  Venus presents the opposite problem. How do you get rid of enough CO2, or block enough sunlight, to battle that Godzilla of a greenhouse? Science fiction has traveled this subject deeply, with varying degrees of scientific realism. The best of it is pretty damn good. The word terraforming comes from a 1942 sci-fi story by Jack Williamson, but the topic was explored earlier, by British philosopher Olaf Stapledon in his masterful 1930 novel, Last and First Men, in which Venus is made habitable by using electrolysis to release oxygen from its oceans. (It seemed like a good idea at the time.4) The most sophisticated fictional exploration of terraforming is in the Mars trilogy of Kim Stanley Robinson (Red Mars, 1993; Green Mars, 1994; Blue Mars, 1996), which follows several generations of Martian settlers, and then terraformers, during a time when Earth suffers from ecological devastation. Through the views and experiences of these Earthlings who become Martians, Robinson explores in detail the physical, ethical, cultural, and political challenges of transforming worlds.

  Is Mars Ours?

  Okay, sci-fi is one thing, but is this even a serious idea? It sounds far-fetched, but so would have a modern city in the Nevada desert or high above the Arctic Circle if you had tried to describe one to our hunter-gatherer ancestors on the East African savannah. Spreading to new environments, including places that once seemed uninhabitable, and modifying them to suit our needs is something humans have always done—and now we’ve learned the hard way that we have the power to change whole worlds. Perhaps we can eventually learn to do it on purpose.

  What if it turns out there are already Martians? It seems pretty clear (I hope) that if we discover an indigenous biosphere thriving in current conditions, then it really changes the equation in a drastic way, and argues against any planetary engineering on Mars. In my view, if there are Martians, then Mars is theirs, and we should tread lightly there. We should explore but perhaps not exploit. Ironically, then, if we are too successful in our current mission to find possible signs of life, we may have to reconsider the next big mission of establishing human bases.

  If we find that Mars has no indigenous life, then our choices about whether, and how, to go to Mars are much less complicated. In that case, I think, the ethical equation is reversed. The brightest prospects for Martian biology may lie in the future, because Earth life may one day choose to spread there. You might ask how we would ever determine, for sure, that Mars is lifeless. Fair question. Such a conclusion may be beyond our present-day science. Yet once we’ve explored Mars thoroughly, and explored the universe more widely, our knowledge of life and planets may become mature enough (e.g., light-years beyond our present understanding) for us to recognize a planet with absolutely no life. In that case, I think a pretty good argument can be made for the moral imperative to bring life to Mars and Mars to life. Why? Because life is the most precious thing of all. Shouldn’t we try to spread it? If you lived in a thriving, luxuriant garden next door to a vacant dirt lot, wouldn’t you want to toss some seeds over the fence, turn that emptiness into another garden?

  Also, life on Earth is tough but not invulnerable. Things can happen to planets that would wipe out all life. Several times our planet has possibly come close. What if the largest mass extinction events had been a little larger? Knowing of another planetary biosphere, either because we discover or implant one, would mean knowing that the existence of all life in the universe does not ride on the fate of Earth. Think of an endangered species living only in one threatened habitat. Any reasonable environmental or conservation ethic would demand our trying to locate that species more widely. Well, as long as we are confined to one planet then all life on Earth is, at some level, like that threatened species. Once our biosphere becomes a multiplanet phenomenon, it is no longer vulnerable to a planet-destroying disaster. It will have come a huge step closer to immortality.

  If at some point we have the opportunity to safeguard life against such a possibility, then, by all that we hold dear, wouldn’t it be our highest moral duty to do so? Earlier I argue that once we gained knowledge of asteroid strikes and the potential to avert them, that became our responsibility. An extension of this same logic could imply a moral imperative to terraform. The greenest of the green philosophies, which treasure the intrinsic value of life above anything human made or influenced, should assign great importance to having life’s domain spread across many worlds.

  I’ve led public discussions on terraforming in classrooms and museums, and once in a church, and found that it gets people talking about our attitudes toward life, nature, and human responsibility and action. I sometimes start by showing a picture taken by one of our Mars rovers depicting its lonely tracks winding back into the distance across a vast, otherwise untouched Martian plain, and ask, “What do you see here? How does it make you feel?”

  Mars rover Opportunity looks back over where it’s been.

  Dune buggy tracks on a beach of Cape Cod.

  Do you see this as an act of vandalism, as the despoliation of an otherwise pristine landscape, equivalent to dune buggy tracks grinding through fragile dunes where seabirds are trying to nest?

  Or do you see it as the mark of an evolutionary moment, equivalent to the tentative tracks left on a lonely beach by the first creature ever to venture haltingly from the sea and onto the land?

  Three-hundred-ninety-five-million-year-old animal tracks in Poland, some of the oldest traces of land animals.

  I understand the former view, but I personally see it more as the latter. This discussion of how we see our presence on an otherwise lifeless world then progresses to the question of our right future action on that world. There is the obvious reaction
of “Hands off the cosmos!” What unbelievable arrogance to think that we can have the wisdom or the know-how to “fix” another world? Haven’t we done enough damage on this one? As Pollack and Sagan put it in their chapter, “Can we who have made such a mess of this world be trusted with others?”

  I find the conversation worthwhile, and as you might have guessed, I like to defend the possible justifications for terraforming against the reflexive reactionary opinions it sometimes evokes. Yet do I think we should terraform the other planets in our solar system? Hell, no. Not if “we” is the human race today, with our current scientific knowledge and institutions. We don’t know what we’re doing, and it would be foolish to pretend we do. It may indeed be our destiny someday to cultivate Mars, but we have to do our homework first. We won’t be ready until we’ve done much more outer and inner exploration and become much wiser about life, on Earth and off.

  These grandiose schemes don’t worry me though, because even if someone decided they wanted to terraform Mars, it’s not like they could just start tomorrow. The option is not on the table. Mars is safe for now. But in the meantime, terraforming dreams can help us think through our perplexing situation as reluctant engineers of our home world. When we imagine ourselves intentionally changing the climate of a planet, it flexes the right mind-muscles, those that will feed our ability to manage our own planet. This is the kind of thinking that humanity will need in order to survive in the long run. We’ll leave Mars alone for now, but we don’t have that option when it comes to Earth.