Earth in Human Hands

by David Grinspoon

  Carl was way ahead of the curve on the consequences of anthropogenic climate change. He was into warning about global warming before it was cool. He was also a fan of terraforming, and saw becoming a multiplanet species as part of the long-term plan of humanity. Yet he was also wary of foolish human tinkering. At the end of their 1993 paper, he and Pollack concluded that:

  Clearly more work is needed, but comparatively inexpensive and environmentally prudent methods of mitigating greenhouse warming on Earth may be within reach in the next few decades.

  Well, here we are now, after the next few decades. As I write this, nearly a quarter century has passed since their paper was written. When I look over the current literature on geoengineering, it remains clear that “more work is needed.”

  I believe that were he here today, Carl would urge extreme caution about geoengineering. I can close my eyes and hear his deep, resonant voice saying, “It would be an act of consummate recklessness and arrogance to try to jury-rig the only home we have, to attempt a quick-and-dirty repair job on the complex, deeply mysterious, and exquisitely balanced global mechanisms that all human life, and all other life we know of, depends upon, when we are still so ignorant about their functioning.” Yes, I know Carl would have found a way to say it more eloquently, but I feel pretty confident I know where he would stand on the issue.

  We are not ready to terraform Mars, or intrusively reengineer Earth, any more than Neolithic humans were equipped to design modern urban sewage systems or the inhabitants of King Arthur’s Court were able to understand the technology of Mark Twain’s Connecticut Yankee. Attempting such a fix now would be completely insane. Or, as my friend, climate scientist Ray Pierrehumbert, one of the coauthors on the recent National Research Council report on geoengineering by solar radiation management,9 put it, trying to do this anytime soon would be “wildly, utterly, howlingly barking mad.” Though there are a few loud voices advocating them, there is not really very much support for these risky quick-fix geoengineering schemes, and as people look into them more carefully, this support will continue to decline. The National Research Council reports released in 2015 endorsed further study but also stated strongly that none of the intrusive climate-intervention schemes should be implemented. The conversation is valuable if anything because it highlights the uncertainties, the incompleteness of our knowledge, and the fact that we really have no choice but to control our CO2 habit. Given how much we have yet to learn, we really should not be let anywhere near the controls of planet Earth.

  Only, it’s a little late for that. Without realizing it, we have grabbed hold of those controls and we’re… not exactly driving. We’re not in control, but we’re madly spinning the wheel, pushing buttons, and turning knobs. We have to try to understand how this planet works, ease up on the switches gradually without letting go entirely, and try to reengage some of the autopilot mechanisms we’ve disabled, while we work on a longer-term plan.

  Sagan and Pollack ended their review of planetary engineering with a statement about Earth:

  A short-term imperative for planetary engineering exists only for one world in the solar system, our own. Careless or reckless applications of human technological genius have put the global environment at risk in several different ways. The Earth is not a disposable planet. It is just conceivable, as we have discussed, that some of the techniques that in the long term might be applied to engineering other worlds might also be utilized to ameliorate the damage being done to this one. Perhaps a safe way to test our protocols is to implement them in carefully circumscribed ways on other worlds. But considering the relative urgencies, a useful indication of when the human species is ready to consider planetary engineering seriously is when we have put our own world right. We can consider it a test of the depth of our understanding and our commitment. The first step in engineering the solar system is to guarantee the habitability of the Earth.

  Roger that, Houston. Yet how do we guarantee that Earth remains habitable, not just for life (which is not really threatened) but for the present biota and a society of (approaching) ten billion human beings? As I’ve discussed, there is no easy, quick fix. Or, rather, there may conceivably be one, but we are not in a position to know about it and safely apply it. Perhaps some wise, advanced technical civilization somewhere in the universe knows exactly how to cure what ails us (more on this in chapter 6). At some future date people may look back on our time and say, “If only they had known.” Just as we can look back and say, “If only we had known about antibiotics in the Middle Ages, the tragedy of the Black Death in Europe could have been avoided,” or “If we had known about the smallpox vaccine in the sixteenth century, the history of indigenous Americans could have been very different and much less tragic.” The aversion of tragedy sometimes comes down not to what is physically possible or impossible, but what is known when.

  Some have, understandably, called for a moratorium not just on the deployment of these technologies, but even on studying them. The Australian environmental philosopher Clive Hamilton wrote an editorial in Nature entitled “No, We Should Not Just ‘At Least Do the Research.’” Along with many others, he feels that even by studying how we might undertake these radical geoengineering proposals, we are making them seem like more acceptable options. He is right to voice concern about this. If we operate with the fantasy that a quick fix is near at hand, and it lessens motivation or pressure to reduce carbon emissions, then the existence of the research program itself would indeed be harmful. Certainly if we are studying these options, we should be extremely careful not to give the impression that—well, that they are options. Yet those who advocate a research prohibition are wrong for three reasons.

  First, studying this makes us smarter about the climate system. Understanding human interactions with other planetary subsystems is now part of learning about Earth. We are already “engineering” it in various ways. Okay, engineering is not quite the right word, as it implies some larger degree of understanding than we have. We are perhaps engineering Earth only in the way that your infant is “engineering” your home media system when she sticks cookies in the DVD slot. Yet if you wanted to figure out why it wasn’t working in the right way, you would not want to ignore this activity.*

  We cannot model the climate system without including, in our equations, factors representing human actions—or we could, but these studies would be irrelevant representations of a world we do not actually inhabit. In fact, there is reason for us to pay particular attention to these terms in the equation: they are the ones that we ought to be able to change. Our collective behavior is now a component of the climate system. So when we talk about changing our own behavior in ways that will have a beneficial influence, we are in fact discussing a kind of climate engineering. We should focus first on our unintended contributions. Only when we get a handle on that will we possibly have graduated to the point of being able to experiment with other terms of the equation.

  Second, we know we will need to intervene eventually, some millennia hence, because eventually climate will change dangerously if we let it. At that point our intervention could save a lot of species from extinction. In the meantime, learning to think on these longer timescales is a necessary survival skill. As I’ve discussed, over the long run, if we have a long run, we will be morally obligated to interfere with Earth’s climate through some form of geoengineering to stop the dangerous climate change that would occur if we left it alone. In the short run, we are obligated to try to have a long run.

  Third, we need to be ready with risky rescue options just in case the very worst-case climate scenarios do unfold and force us to try something desperate. Global warming could conceivably become rapidly more intense than our best models predict. Complex systems with positive feedbacks do contain “tipping points,” where new modes of behavior can suddenly emerge. Some of the scarier scenarios involve the release of vast methane deposits trapped on the seafloor, or frozen in the Arctic tundra. There are projections where the release
of these reserves starts to warm Earth, triggering further release, and causing a rapid runaway effect. There are other scary outcomes in which the Antarctic ice sheets could collapse rapidly and spectacularly, causing a sudden huge rise in sea level. Earth’s climate record seems to show some episodes where the system jumped quickly to a significantly warmer state.

  I don’t believe these are the most likely paths for Earth’s climate in the next couple of centuries. My sense is that there are too many complex negative feedbacks built into the system to let one of these positive feedbacks completely take over, and even given the unprecedented provocation we’re introducing, the system tends to move slowly on human time. The climate change I’m personally most worried about is the kind we can reliably predict will progress throughout the next century if we continue on our current course: the slow, inexorable warming and acidification that is already under way. But the fact that we can’t rule out the scarier, rougher scenarios is deeply unnerving, considering what is at stake. Given this, it is our duty to research the more intrusive geoengineering options now. At the same time, we need to be doing everything we can so that we never need to use them.

  Would you be comfortable about someone trying to reengineer, during flight, an airplane that you and your family were flying in? No, of course not. Unless you knew the plane was in trouble and going down. Then you would probably very much want them to try something. We don’t want to be in that position with our planet, and with a little luck and a fast learning curve, we won’t be. Still, just as NASA builds safety contingency plans into missions, and hopes never to use them, we need to have contingency plans for the possibility that planetary climate could take a sudden turn for the worse.

  We Are Apprentice Planetary Engineers

  We have no choice at this point but to engineer Earth, in the sense that we need to thoughtfully interact with it. Our actual choice is between methods: what kind of planetary engineering we should undertake, how and when we should intervene in the Earth system. We should regard ourselves now as apprentice planetary engineers, easing up on those behaviors that have been throwing the system out of balance, taking those steps we know are safe, and learning all that we can about how the system works so that by the time we need to call upon more intensive interventions, we will be ready to do so safely and wisely.

  The most necessary and near-term geoengineering strategies are the least intrusive: moving to alternative energy, reducing our emissions of greenhouse gases, intensifying agriculture to take up a smaller land footprint, and halting and reversing deforestation. Then there are somewhat more intrusive schemes that must be employed only with caution, after further study, and starting on a small scale, such as ocean fertilization. On the other end of the continuum are those that, given our current level of knowledge, would be far too risky to attempt, such as artificially clouding the stratosphere.

  On the most basic level of systems engineering, we can see that we have been unconsciously acting to promote positive feedbacks in the climate system, and these increase instability. Yet the mere fact that we are now studying this system, including our own role in it, potentiates a huge change to planetary dynamics. With awareness comes the possibility to alter, and reverse our role. First we can learn to stop our unconscious destabilization. Then we can choose to introduce more negative feedbacks. We can shift to being stabilizers.

  The best way to change the equation right now is to enact a “sign change” on one quantity in particular: the rate of accelerating CO2 input into the atmosphere. Our urgent task is to shift that from positive to negative. The more we learn about how the system works, and the role we are playing in it—and the more we share and spread this knowledge—the more impetus is created to enact this change. That’s going to be tricky, but we are going to do it. There’s no doubt about that. Fossil fuels won’t be around forever and, over time, will only become more expensive, and their extraction more difficult and ruinous. Timing is everything, though. It takes a generation to transform a civilization’s energy system, so we had better hurry up. Alternative energies are getting cheaper and more widespread. Fossil fuels are gaining more and more of a deserved stigma, but economic forces are slow to change. Also there is another dynamic at play that needs to be spelled out even in this very basic discussion of energy futures: the developing world needs and deserves a lot more energy. Hundreds of millions are in need of lights, sanitation, and so much that we in my country take for granted. If we want them to do this without burning coal—and believe me, we do—then we have to help them.

  The Earth system can absorb a certain outflow of CO 2—it’s been doing that for a lot longer than we’ve been here. It’s easy to imagine a global technological civilization that dumps some amount of carbon into the atmosphere without causing long-term climate change. If we hadn’t already pushed things so far out of whack, with an excess atmospheric carbon load that will last for thousands of centuries, this inevitable deceleration of our carbon effluence might ultimately prove to be enough. Yet given how far we are pushing the system, we are going to need to think about taking our level of engineering intervention up a notch and enacting a second “sign change” in the equations: transform the total human input of CO2 into the system from positive to negative, actively removing some CO2 to help restore balance. As I’ve just discussed, the most unobtrusive way to do that would be by planting lots of trees. The more intrusive ways include ocean fertilization, algae farms, genetic engineering, and artificial photosynthesis.

  Some might object at all to calling the greener, less intrusive steps “geoengineering,” but they are conscious choices, enacted at a global level, to change properties of our planet. The more hard-core, brute-force methods we usually associate with the term geoengineering are, appropriately, more controversial. We certainly don’t want to make the cure worse than the disease. Still, they are all on a continuum of actions we might take purposefully to change the planet.

  Returning to the medical analogy, consider the sometimes false dichotomy between “natural” medicine and more invasive and aggressive interventions. Any good doctor will tell you that you need both. It is always a good idea to do what you can to maintain and restore health with nutrition, diet, and lifestyle, fostering your body’s own homeostatic tendency toward health and equilibrium. Yet sometimes you need medication or even surgery or chemotherapy. In these latter cases you wouldn’t want to try a cure that had never been tried and tested, but if you found yourself or your loved one in rapidly declining health, you might gladly sign up for an experimental trial.

  It’s interesting to compare intrusive geoengineering with planetary defense against dangerous asteroids. Each of these is a capacity that, with luck, we won’t need right away but we know we’ll have to call on eventually. In both cases we can’t afford not to study the problem to increase both our awareness of the dangers and our ability eventually to act. This means better and more complete Earth observations, better climate modeling, more thorough planetary exploration, and more complete surveying of the small-body population of the solar system, so we know just what we’re dealing with. To gain both the knowledge and the wisdom to undertake such solutions, we’ll need to keep exploring other worlds and integrating what we learn about how climate unfolds in different planetary scenarios.

  On the longer timescales (tens of thousands of years) over which Earth will go through huge climate changes, and more likely than not enter into the path of some very dangerous space rocks, it will be essential to know how to meet these threats.

  Certainly if there is still a human civilization on Earth within one hundred thousand years (ten times longer than there has been one to this point), we will have employed both these defense mechanisms. Either one might be needed much sooner—in the case of climate, if worst-case scenarios and feedbacks are underestimated or unknown, and in the case of planetary defense, if we get unlucky or decide to mitigate against those smaller, more frequent impactors that would not decimate civilization but could
destroy cities.

  Especially as long as humanity, and all life, is confined to one planet, we are obligated to study these problems and learn how to intervene intelligently when the alternative is catastrophe.

  Yet we are also morally forbidden from trying either of these technologies on any large scale at this point. Planetary defense, like climate engineering, is not without risk if attempted ignorantly. If we’re changing the trajectory of giant space rocks that could cause calamitous impacts, we need to know what we’re doing. Here also there will be difficult governance issues. In the case of long-term climate intervention, once we have moved beyond the emergency mitigation of dangerous warming, there will be the question of who gets to set the thermostat, and where it should be set. Governance challenges for planetary defense may arise, for example, if a city-destroying space rock is found to be heading for an impact point in a particular country. Altering its trajectory will mean, at first, that other countries are put in the crosshairs before it is safely deflected to miss Earth entirely. We’ll need to temporarily increase the risk for some in order to save others. Those placed in harm’s way will need reason to feel confident that the system will continue functioning long enough for us to finish the job. These problems can be surmounted, but we’ve got work to do on the technical, political, and cultural fronts.

  In the case both of planetary defense and global warming, the larger challenge is the same: to become aware of ourselves as actors in a planetary system that is evolving over timescales much longer than our individual lives. We need a long-term plan for humanity’s future. It needs to be flexible and to include a wide continuum of solutions, but we need to start enacting it now, knowing full well that the plan will change as events unfold and our knowledge increases. Part of dealing with uncertainty ought to be the realization that we need approaches that are sustained but flexible, subject to modification when we see how the planet actually responds to our poking and prodding. It is essential that we research much more extreme or risky maneuvers than we ever hope actually to use.