Astronomer Carl Sagan, in the 1960s and 70s, detailed how this might be done both with Venus and Mars. For Venus, a planet with a greenhouse problem far worse than the Earth’s, Sagan suggested seeding its atmosphere with algae, which would lock water, nitrogen and carbon dioxide into various organic compounds. As carbon dioxide was removed from the atmosphere, temperatures would drop to “comfortable” levels. Unfortunately, later findings showed that the clouds on Venus are far thicker than previously believed, and they contain such high levels of sulfuric acid that algae would not be likely to survive.
The problem on Mars is the opposite: terraforming the red planet would require building up a suitable atmosphere and warming it. NASA was sufficiently intrigued with the notion of making Mars habitable that it held several conferences following up on Sagan’s ideas. The general idea for Mars is to unlock the carbon dioxide in the planet’s ice cap in order to increase its atmospheric pressure, and then to use phytoplankton to create a balanced atmosphere. As the planet warmed up, its frozen reserves of water would become accessible, allowing for the introduction of plants.
While re-engineering Mars to suit human purposes is theoretically more feasible than dealing with Venus, the effort involved would be enormous, since vast quantities of materials would have to be brought to the planet. Depending on the methodology, it would require the mining of ammonia on asteroids, methane or other hydrocarbons on Saturn’s moon Titan, or the mining of fluorine on Mars itself. There are also suggestions for space-based mirrors and the diversion of small asteroids to crash into the Martian surface.
Most of the schemes for doing this assume the development of self-replicating robot technology to carry it out. In other words, a well-programmed set of unmanned robotic craft is sent out to Mars, Titan, and/or the asteroid belt, and they proceed to mine materials and fuels for self-replication and self-maintenance as well as to carry out their mission of delivering supplies for the modification of Mars. Meanwhile — and this could be a period of hundreds of years — humankind would patiently wait for the planet’s terraformation before booking any vacations.
In the movies, such as in the Star Trek series, this inconvenient interval is bridged by the invention of a handy terraforming gadget called the Genesis Device, capable of reshaping a planet in a matter of hours, but even in Star Trek, the Device turns out to have flaws and ultimately backfires, so we can only count on very slow planetary transformations. And before we even start, we probably need a vast improvement in our ability to build digital models of planetary systems so that we can fine-tune the artificial environments we build there. But this, also, could eventually happen when very sophisticated computers themselves learn to build even more sophisticated computers.
Terraforming, or partial terraforming, has also been proposed for Mercury, for Jupiter’s moons Europa, Callisto, Ganymede, and Titan, Saturn’s moon Enceladus, for our own Moon, and for the dwarf planet Ceres, which orbits between Mars and Jupiter.
Now, all of this is great fun to think about and has been fodder for lots of interesting science fiction plots. But the subject of this paper is the terraforming not of Venus or Mars, but the planet between them, our own terra firma. We have been unintentionally terraforming our world for millennia. The question is whether we should now consider some intentional terraforming, or geoengineering as the concept is more often called in reference to Earth, to counteract the negative consequences of our own activities.
Let’s have a look, first, at the unintentional modifications we have been making to our planetary habitat. They are not limited to the currently most debated one, global warming due to increased carbon dioxide levels, and other climate changes resulting from increased temperatures. We have been at this for thousands of years, although our impact has vastly accelerated over the last hundred years or so.
Consider a few of the alterations we have wrought, and are still inflicting on the Earth:
Until the middle of the twentieth century, the earth had a stable area of about 6 million square miles of tropical forest. Since 1947, about half of that has been cut down, and at the rate it is disappearing, only about 10 percent of the original area will be left by 2030 — 17 years from now. But this is just the latest chapter in the disappearance of the world’s forests. Nearly all of the original forest that covered much of Europe was cut down between by the year 1500 to supply the needs of that continent’s growing population. Norman Cantor described this in The Civilization of the Middle Ages as follows:
Europeans had lived in the midst of vast forests throughout the earlier medieval centuries. After 1250 they became so skilled at deforestation that by 1500 they were running short of wood for heating and cooking. They were faced with a nutritional decline because of the elimination of the generous supply of wild game that had inhabited the now-disappearing forests, which throughout medieval times had provided the staple of their carnivorous high-protein diet. By 1500 Europe was on the edge of a fuel and nutritional disaster [from] which it was saved in the sixteenth century only by the burning of soft coal and the cultivation of potatoes and maize [fortuitously imported from the newly discovered Americas].
2. Wetland drainage
Just as humans have rarely encountered a forest they didn’t want to cut down, they have been even more eager to drain any swamp or other wetland they found. Not only were swamps seen as economically unproductive, they appeared to be refuges for wildlife destructive of crops. In the United States, although they are now better protected, more than half of the original wetlands have been eliminated. Globally, the figure approaches 60 percent. And if a wetland sits in the way of development, there are still often convenient ways to get around restrictions by creating equivalent wetlands elsewhere. In other words, geoengineering our way around the problem.
3. Destruction of ecosystems and elimination of species
Humans have deliberately as well as accidently eliminated many species, beginning in prehistoric times. Climate change and ecosystem change following the last ice age decimated populations of the woolly mammoth in northern Europe and Asia, but human hunting is believed to have contributed significantly to their extinction. In North America, half of the large mammal species — including mammoths, mastodons and giant ground sloths — disappeared very suddenly about 13,000 years ago, precisely at the same time that humans spread their way across the continent. Human causation remains unproven — other factors like ice-age climate changes could have been involved, but there is no doubt that early humans had a significant impact on many ecosystems. These impacts can be found and studied with accuracy in isolated ecosystems such as those on Pacific islands. Along with hunting, human impacts came from activities like burning of forests to create space for agriculture, and from the importation of non-native species like cats, dogs, pigs, rats and microbes. Even marine ecosystems in coastal area, lakes and rivers were impacted by early human activities.
4. Ocean acidification
Rivers and streams have carried the detritus of human civilization to the ocean since prehistory, but since the advent of the industrial revolution in the 18th century, our use of the seas as a waste repository has gradually increased its acidity, and this trend has been accelerated by the absorption of CO2 from the atmosphere into seawater. While this absorption helps mitigate the effects of atmospheric CO2 injections by human activity, it spells disaster for marine life. The current rate of acidification is 100 times faster than any changes over the last 20 million years — a habitat modification that is certain to have an enormous effect on marine organisms that cannot adapt fast enough to the change. We are already seeing the deaths of coral reefs and impacts on spawning activities on the continental shelves.
5. Alteration of natural land uses
We have covered thousands of square miles with cities, many of them with minimal green space, and with roadways connecting cities and towns. More than 61,000 square miles of the United States is paved for roads and parking lots — that’s a little more than the state of Georgia, but smaller than Wisconsin. As it happens, this is about the same amount of land we plant with wheat each year. Which brings us to:
6. Agricultural activities
Keep in mind that planting wheat, and every other kind of agriculture, is also a form of terraforming, of artificial transformation of the planet’s surface to suit our needs. In the U.S., counting all 50 states, we use about 27 percent for pasture and rangeland for animals, and 18 percent to grow crops. Our cities, towns and rural residential areas take up about 6.8 percent. By the way of that, 46.5 million acres, about 2 percent of the land area of the 50 states, the equivalent of Pennsylvania, Delaware and Rhode Island combined, consists of our monocropped lawns, one component of the terraforming activities that each of us is personally engaged in. Overall, only about 11 percent of the surface of the United States consists of parkland and wildlife areas, and another 24 percent is forest, much of it actively managed for timber. So about 35 percent of our country is in a relatively natural though certainly not pristine state, and 65 percent is altered to a greater or lesser degree by human uses.
On a global scale, the pattern is not very different. More than 40 percent of the earth’s land surface is given over to agriculture. About thirty percent remains forested, but again, much of that is actively managed or otherwise vulnerable, and as noted earlier, those forests are disappearing rapidly.
I cite all these facts and statistics to make the point that since prehistoric times the activities of humans have actively shaped their environment and turned nearly every region of the earth into something much different from what it would be if humans had never evolved on earth. Our current biosphere is what it is largely because of intentional as well as unintentional geoengineering by humans. When you visit the Netherlands, you’ll hear the saying that “God made the world, but the Dutch made the Netherlands.” And that’s true, because much of the country simply would not exist if it were not for centuries of dike-building, marsh drainage, and continual pumping of water from areas below sea level. But on a global scale, the same thing is true. God made the world, but humans have pretty thoroughly remodeled it to suit their needs. In the long run, we’re going to have to slow down the pace of the changes we’re making. But to get to some kind of long-term stability scenario, we may have to consider taking some steps that are even more radical than those we have historically taken.
The problem we face is that some of the effects we are having on our planetary home are clearly not sustainable, and will soon begin to have unpredictable, almost unimaginable consequences. We know for a fact that the carbon dioxide we are spewing into the atmosphere, liberated from fossil fuels that kept the carbon locked up for millions of years, is elevating the average temperature of the atmosphere at an increasing rate. That might not be so bad by itself, but the increase is having consequences that are all predicted to get worse: melting glaciers and polar ice that will raise sea levels and flood huge coastal areas, more extreme weather of all kinds including more intense storm systems, droughts in some areas, excessive rainfall in others, stressing and extinction of plant and animal species, and ocean acidification.
There will also be huge social impacts, including famines and wars, resulting from all of these effects, especially from flooding of coastline cities and agricultural regions. Beyond all this there could be as yet unforeseen consequences such as the alteration of major ocean currents and weather patterns, and increases in volcanic activity and earthquakes due to the tectonic effects of the removal of the weight of glaciers and ice caps from the earth’s crust.
All in all, this is not a comforting vision. And the worst part is that right now, none of the efforts to do anything about it are having any real impact at all on the problem. Yes, the United States and other countries have reduced their carbon emissions. U.S. emissions are down about 11 percent from 2005 levels. Some attribute this reversal to new energy-saving technologies, gains in efficiency and increased use of renewable energy sources. But Congress never passed any real carbon-reduction plan and the U.S. has refused to ratify any international agreements on emission reductions. Instead of a planned reduction, we have a reduction mostly by happenstance: the recession and continuing economic sluggishness played a part, and the rapid development of hydraulic fracturing technology and the consequent surge in natural gas usage account for most of the reduction.
The European Union has also cut its emissions and has actually been fairly stable since about 1980. But meanwhile global emissions of carbon dioxide rose to a record high in 2012, with a one-year increase of 2.6 percent. Carbon emissions are now 58 percent higher than they were in 1990, and the global rate of increase has not slowed down at all. A huge increase is coming from Asia. So the atmospheric concentration of carbon dioxide continues to rise. It is now 392 parts per million, well above the level of 350 parts per million that many environmentalists see as a red line — a level to which we must return to avoid irreversible consequences. Not only are we well beyond 350, we are growing by two or three parts per million per year, and we nothing in place to stop that trend, let alone reverse it. No political agreements. No reductions in the global amounts of carbon-based fossil fuels we are burning. Clearly no indications on the part of China or other major developing countries to even slow down growth in carbon emissions until they achieve economic parity with the US on a per-capita basis. And by the way, we really are not about to run out of these fuels. The jury is very much out on whether we have actually reached the so-called peak oil stage, and even if we have, it means we’ve only used up half the world’s oil and still have 50 percent left to burn. And even if we used that up, we still have hundreds, perhaps even thousands of years of coal and natural gas supply left.
So the big problem the world faces is that any process we can imagine by which developing countries can approach economic parity with the developed world involves massive increases in their use of energy. While we can certainly encourage that to happen as much as possible with renewable energy, the fact is that as long as renewable options are more expensive, and as long as fossil fuels are there for the taking, they will be taken. As a consequence, global emissions could actually double or triple over the next half century before even beginning to level off. Global temperatures would continue to rise much longer.
So what are we to do? Option One falls under the rubric of sustainability. It boils down to: “let’s all collectively do the right thing, creating sustainable economies with sustainable energy systems.” This is pretty much the working scenario— to stabilize, and then gradually reduce, the world’s carbon emissions by throttling the fossil fuel usage of the developed world, while at least dampening the rate of increase in the developing world. The Kyoto Protocols, which originally intended to stabilize atmospheric CO2 at 400 parts per million, tried to accomplish this, and failed. We will pass that target level in a few years, without even slowing down. There have been annual followup gatherings and agreements, notably in Copenhagen and Doha. The stabilization target has now been reset to 450 parts per million, which is estimated to have a 50-50 chance of limiting the average temperature increase to 2 degrees Celsius by the year 2100.
Option One, in my opinion, is simply not going to work. If it were discovered that an asteroid were heading our way, the world might very wel decide that it is in our collective best interest to work on a plan to deflect it. We actually did, collectively, decide to stop producing chorlofluorocarbons to propel our shaving cream and spray paints, when we realized that these chemicals were going to deplete the ozone layer and give us all skin cancer. This was accomplished in 1987 under the Montreal Protocol on Substances that Deplete the Ozone Layer, a treaty ratified by every single member of the United Nations as well as several non members and the European Union.
But unfortunately, the threatened impacts of global warming are not as real as those posed by asteroids and chlorofluorocarbons. At least not yet. It’s certainly possible that the many uncoordinated but significant efforts by individual families, communities, companies and governments around the world will have mitigating effects. But as long as overriding economic interests, and very real issues of fairness and equity with regard to living standards between developing and developed nations, get in the way of dealing with global warming, we are not going to get the kind of unanimity that such threats as asteroids and ozone depletion are able to garner.
So, what’s option two? While Option One hopes for sustainability, option two suggests resilience — the ability to adapt to challenges and new situations, recognizing that things may not stay the way they’ve been or the way we’d like them to be. The resilience option says we must put a priority on effectively adapting to the climate changes we know are coming. The concept of resilience also entails preparedness at a local level for things like interruptions in power or localized flooding, but let’s confine our thinking to the mega-projects that will be needed to deal with the larger effects of climate change.
Resilience means smarter design of cities, buildings and infrastructure. It means not rebuilding in coastal areas and river valley areas that are prone to flooding, but moving communities to higher ground. It could mean the construction of huge barriers at the harbor entrances of major cities like New York. The Dutch, who raised their dikes and built massive flood barriers after their national disaster of 1953, are raising their dikes once again to prepare for higher tides. Resilience planning is not simply defensive — it puts a real premium on working with nature rather than against it. So for example, various nations have proposed the construction of floating cities in which higher water levels become irrelevant.
Resilience also means adapting crops to warmer temperatures, and finding ways to mitigate the inevitable ecological challenges that will arise when native species of flora and fauna are stressed or made extinct by climate change. And planning for resilience means being ready for the human consequences of climate change — the economic and sociological effects of migration necessitated by rising sea levels, the health impacts of higher temperatures, frequent floods, damaged water and sewer systems, and so forth. Resilience means developing better early warning systems for storms and floods, and more effective evacuation procedures.
But is it realistic to limit our response to options one and two? Will striving for sustainability while planning for resilience save the planet? We really don’t know. The EPA’s projections for parts per million of CO2 include scenarios ranging from stabilization at around 450 PPM, to indefinite growth with more than 1000 PPM by the end of this century with no stabilization in sight. Under these scenarios, projected global average temperature increases by the end of the century range from 2 degrees to 11.5 degrees Fahrenheit. Sea level increase projections range from two feet to six feet. Enormous amounts of methane, now locked under frozen tundras, would be released, exacerbating the greenhouse effect.
It’s natural to hope for the less problematic end of these scales, but the reality is that sea level is currently rising about 60 percent faster than the UN’s best projections in 1993. Part of the problem is that we have no idea how fast the Greenland and Antarctic ice caps may melt, but the melt rates in those areas and most other glaciers continues to proceed faster than expected. If the Greenland and Antarctic ice caps melted in their entirety, as they certainly might if CO2 levels rose beyond 1000 parts per million. oceans would rise nearly 200 feet. No one expects that to happen, but even a little more melting in those areas than currently expected could translate into several feet of additional ocean rise and make all current coastal defense systems obsolete. If we refuse to observe the red lines drawn at 350, 400 or 450 part per million of atmospheric CO2, we must certainly observe a red line at some very moderate level of ocean level rise.
This brings us to Option 3, the terraforming or geo-engineering option —implementation of actual countermeasures on a global scale to counteract the warming effects of greenhouse gases. And surprisingly, at least one Option 3 strategy is technically simple, and not terribly expensive. It doesn’t involve mining asteroids or building self-replicating robot fleets. Should we reach a global consensus that Options 1 and 2 are not working well enough, the basic blueprint is ready to roll. We’ve got a little time to think about it, to do more research on its side effects. And once we start it up, we can gear it up slowly so as to monitor how it’s doing and calibrate it as we go along. Should we decide that sustainability and resilience are not saving the day, here’s what’s involved in the terraforming option, as described in a recent Technology Review article:
Here is the plan. Customize several Gulfstream business jets with military engines and with equipment to produce and disperse fine droplets of sulfuric acid. Fly the jets up around 20 kilometers—significantly higher than the cruising altitude for a commercial jetliner but still well within their range. At that altitude in the tropics, the aircraft are in the lower stratosphere. The planes spray the sulfuric acid, carefully controlling the rate of its release. The sulfur combines with water vapor to form sulfate aerosols, fine particles less than a micrometer in diameter. These get swept upward by natural wind patterns and are dispersed over the globe, including the poles. Once spread across the stratosphere, the aerosols will reflect about 1 percent of the sunlight hitting Earth back into space. Increasing what scientists call the planet’s albedo, or reflective power, will partially offset the warming effects caused by rising levels of greenhouse gases.This is not the idea of a crackpot scientist, but a well-vetted, though controversial proposal by David Keith, a professor of applied physics at Harvard. Keith calculates the annual cost, at full deployment in 2040, would be about $700 million per year to completely balance out the warming effects of carbon emissions. A key point is that the amount of sulfur needed is a small fraction of the sulfur that’s already annually spewed into the atmosphere, but that sulfur mainly stays at lower altitudes and is washed out of the air by rain. Sulfate particles injected into the stratosphere will stay there for several years. And this geoengineering process has the key benefit of actually being able to reverse the temperature increase — to turn down the thermostat and re-freeze the polar seas, even if carbon emissions continue unabated. By contrast, if somehow Option 1 were able to halt all emissions tomorrow, or at any point along the projected emissions curve, the atmospheric warming we have already caused, and all of its consequences, would not subside for many hundreds of years. Keith himself doesn’t want to begin geoengineering any time soon, and urges that emissions be cut as much as possible. But if that doesn’t work, and I’ve laid out the reasons why I don’t think it will work, there’s a solution on the table.
There are certainly unanswered questions in this terraforming scheme. The potential side effects, such as how sulfate injections might affect precipitation, are not known. Keith suggests carrying out experiments at a very limited scale, but many scientists oppose that on the grounds that once first steps are taken, full scale deployment would become too tempting, too easy a solution as against the preferable path of throttling emissions. Moreover, we have in place no decision-making process, no governance structure for a global terraforming project. And there is likely to be fierce opposition from folks like the chemtrail conspiracy theorists, who believe that the ordinary contrails of commercial and military jets are evidence of some kind of geoengineering scheme.
In any case, since the potential benefits of sulfate injections would come relatively quickly after the start of the program, we have some time to work on these issues. Perhaps NASA should convene some more conferences on terraforming, not to talk about Mars or Venus, but about our own planet.
Unfortunately, this sulfur injection plan would not solve the equally significant problem of ocean acidification. In fact, since sulfur seeding would not actually affect the accumulation of CO2 in the atmosphere, but rather permit it to continue unabated, the absorption of CO2 into the oceans that causes acidification would continue as well. So, once we decide on the terraforming option, we’ll need an aquaforming solution as well. There are some ideas, but they are not as cheap or simple as that fleet of Gulfstream jets.
One suggestion involves building a fleet of floating factories, fueled by wind and solar power, which would extract carbonic acid from seawater to produce synthetic fuels such as methane, gasoline, diesel fuel, jet fuel and ammonia. To prevent these fuels from returning CO2 to the atmosphere, this plan requires carbon capture and sequestration during the combustion process. One can imagine this combustion taking place on the same floating platforms, generating electricity which would in turn desalinate water, thus addressing another pressing human need.
Another proposal to mitigate ocean acidification involves iron fertilization of upper ocean layers. This would stimulate the growth of phytoplankton, which would convert dissolved CO2 into carbohydrates that would sink to the ocean floor. While the phytoplankton would potentially benefit the marine food chain, the lowering of acidity at the upper ocean layers would come at the expense of higher acidity at deeper levels.
Ultimately, terraforming options for the atmosphere and the oceans should be seen as temporary measures — perhaps continuing for a century or so, not forever. They will give us time to work on the better solutions of resiliency measures, and ultimately, sustainability. But we don’t really know what a sustainable long-term human-dominated ecosystem for earth looks like — how many humans can the earth support, at what standard of living? Just answering those questions could take a century, and arriving at a stable and sustainable biosphere could take another century, or longer. Meanwhile, the terraforming options could allow us to get from here to there.