In 2006, James Hansen, noted climate activist and at the time director of the Goddard Institute for Space Studies, made a dire prediction. “We have at most 10 years, not 10 years to decide upon action, but 10 years to alter fundamentally the trajectory of global greenhouse emissions,” he wrote. If we fail to do so, he added, “Climate disasters will become unavoidable.”
It is now more than a decade later, and the trajectory of greenhouse gas emissions has not been fundamentally altered. Yet, we should not be too quick to laugh Hansen out of court. His claim was not that the earth would cease to exist in 10 years and that one day only dangerous levels of global warming would become unavoidable if emissions were not cut, although on the latter point he was right. Under any realistic scenario, humanity has already committed to pump enough greenhouse gas into the atmosphere to raise global temperatures to levels not seen for thousands of years.
But this is not the end of the story. As the prospects for limiting global warming solely through emissions cuts have dwindled, scientists are giving more attention to technology that could counteract this, either by sucking carbon dioxide out of the air or by using heat blocking particles to cancel the warming from trapped heat. Known as geoengineering, these techniques are likely to be the subject of a major report by the United Nations panel on climate change. Despite its potential importance, however, geoengineering has yet to enter the popular consciousness.
Some geoengineering ideas sound like something out of science fiction. One common idea is known as solar radiation management. This proposes spraying particles into the upper atmosphere that will reflect sun rays and thus have a cooling effect. But as strange as solar radiation management sounds, it has a firm scientific basis. The huge eruption of Mount Pinatubo sent 20 million tons of sulfur dioxide into the atmosphere. This resulted in average temperatures dropping by nearly one degree from 1991 to 1993.
One advantage of solar radiation management is that it is cheap. Injecting enough particles to stabilize temperatures would be in the range of a few billion dollars a year, easily within the ability of some developing countries or even wealthy individuals. The flip side of all this is that solar radiation management would be difficult to control. While it would keep average temperatures constant, the cooling would be uneven, and there could be unpleasant side effects, many of which are as yet poorly understood. The “unnaturalness” of this technology has also raised political opposition.
Other geoengineering technology would counteract global warming by removing carbon dioxide from the atmosphere. Some of this technology sounds more politically acceptable in the abstract, even though many of the same considerations raised against solar radiation management would also apply to them. Various types of carbon removal technology are also very costly and may require significant tracts of land to operate at scale.
Most of the opposition to all forms of geoengineering is based on moral hazard. If people knew that there was an inexpensive way to guard against global warming that did not require costly emissions cuts, why would they cut emissions at all? Some have even opposed preliminary research on geoengineering on these grounds. This approach is wrongheaded. Even without geoengineering as part of the conversation, the efforts to reduce greenhouse gas emissions have been small and lackluster. Governments may promise big emissions reductions in the future, but insofar as these promises have proven costly, they have not followed through on them.
Far from discouraging climate action, more talk about geoengineering could increase support for emissions reductions. In the last few years, opponents of climate action have been shifting their arguments from saying that global warming is not a problem to saying it is too late to do anything. The potential for geoengineering to provide a temporary stop gap while emissions are reduced shows this is not true. Some research also suggests that people become more receptive to climate solutions generally when they hear the geoengineering idea, perhaps because it underscores just how serious a problem climate change can be today.
Geoengineering raises a host of scientific, political, and even moral and philosophical issues. While some may find it an interesting trick to solve our global climate problem, others view it as strange and disturbing. But climate change is not going away in the future, and it is time we started to talk about geoengineering as a possible part of the solution for our planet.
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