Geoengineering for Atmospheric Restoration
ROBERT B. JACKSON
A few decades ago, the notion of actively controlling Earth’s climate resided primarily in the writings of science fiction authors such as Frank Herbert, Isaac Asimov, and Arthur C. Clarke.
Today, planetary engineering is being discussed openly by scientists and policymakers in Congress, the UK House of Commons, and many other settings.
Clarke’s advice apparently struck a chord: “Politicians should read science fiction, not westerns and detective stories.”
Geoengineering can be thought of as intentionally manipulating Earth’s climate to offset the warming from greenhouse gas emissions. Its activities can be ...view middle of the document...
It can also be industrial. Industrial options include using chemicals to capture CO2 from the air, with renewable energy regenerating the chemicals, or mining silicates or other geologic materials that react naturally with CO2, reburying the deposits after they have absorbed carbon. Whether biological or industrial, the goal of the activities is to reduce greenhouse gas concentrations in the air.
The second type of geoengineering reflects or blocks sunlight to cool Earth without reducing CO2 concentrations. Some commonly proposed “sunshades” include placing dust into the stratosphere with rockets and airplanes, placing space mirrors between Earth and the Sun, or increasing the extent and brightness of ocean clouds. Sunshade approaches are conceivable because reducing sunlight by a couple of percentage points is all that is needed to offset the warming from a doubling of atmospheric CO2. There is a natural analog for this approach: volcanic eruptions, such as Mt. Pinatubo in 1991, which blasted sulfur dust into the stratosphere and cooled Earth by 1° Fahrenheit for more than a year. A concise description of both types of approaches can be found in the Royal Society report Geoengineering the Climate, published in 2009.
Sunshade and carbon removal approaches differ in how fast they can be applied and what they will cost. Sunshade technologies could be applied quickly and fairly cheaply to reduce Earth’s temperature, at a price of perhaps several billion dollars per year and within months of a policy mandate for stratospheric dust seeding. This combination of speed and cost is the main reason why sunshade approaches are being discussed. No other technology allows us to alter the effects of global warming so quickly if Earth’s climate begins to spin out of control.
In contrast, carbon removal technologies would take decades to scale up, at significantly higher cost. For instance, at a price or tax of $100 per metric ton of CO2—roughly five times the European CO2 price in May 2010 but cheaper than industry can scrub CO2 from air today—removing a billion tons of CO2 using industrial approaches would cost $100 billion. Removing the entire fossil fuel emissions from the United States would take about $600 billion annually, and $3 trillion would pay for removing the 30 billion tons of CO2 emitted globally each year. These numbers dwarf the cost of sunshade approaches, even if cheaper biological options such as tree planting can help bring the price down.
How should we think about the geoengineering option? One promising model resides in the principle of restoration. In a well-cited primer from 2004, the Society for Ecological Restoration defined ecological restoration as “the process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed.”
We propose to extend the concept of restoration to the atmosphere, suggesting the term “atmospheric restoration” as a guiding principle for prioritizing geoengineering efforts. The...