This is a topic I’ve increasingly become involved with over the past few years. I’ve taught a couple of Geoengineering courses at Colby College in Maine, and have several research projects that are directly or tangentially associated with aspects of greenhouse gas (GHG) removal, only one of them fits in the Geoengineering category, more on that later.
There is a general scientific consensus now that reducing GHG emissions alone is not going to be enough to keep global temperatures below a 2°C increase by the year 2100. Achieving this benchmark is viewed as necessary to prevent global warming induced changes to the environment of a scale that could threaten human civilization. To meet these goals will require active measures to capture and remove GHG’s, principally CO2 and methane from the atmosphere in addition to substantial reductions in emissions.
Geoengineering as popularly defined is attempts to do large regional, or even planetary scale efforts to mitigate the impacts of global warming. These range the gamut from injecting aerosols into the atmosphere to block sunlight from reaching Earth’s surface, to putting giant mirrors out in space to reflect some sunlight from reaching Earth, to a plethora of ways to try to remove GHG’s, principally carbon dioxide, from the atmosphere. GHG removal generally falls into one of two categories, either enhancing natural processes for capturing and removing CO2 from the atmosphere, or developing novel technical approaches for capturing CO2 and storing it.
Of course, the concept of Geoengineering is controversial, as well it should be. Specifically trying to intentionally modify Earth in such a way as to control planetary climate poses lots of risks. In many cases, we barely know enough about the processes that the solution is trying to use to control climate as to have a clue about a) whether or not it will work in practice (as opposed to theory), and b) what are the unintended consequences, or will the unintended consequences be worse than the problem it is trying to solve. It would be nice to set out a rational 20 to 30 year course of research, starting from testing foundational aspects of different approaches, and then to scale-up of those that look most promising. This would allow us to learn what are the capacities and limitations of any geoengineering approach, if there are synergisms between approaches, and how to mitigate the associated risks.
On the other hand, it’s reasonable to argue that humans embarked on geoengineering of the planet with the advent of systematic farming practices 10,000 years ago, and then 200 years ago scaled these efforts up dramatically with the industrial revolution, and rapid increases in both population and greenhouse gas emissions. So planetary scale manipulation of the environment, especially with little concern for the consequences is definitely not a new thing for us. The reality is that our approach to geoengineering is likely to be ad hoc as well, and time really does seem of the essence. We need to pretty quickly move beyond socio-economics analyses of different approaches, for which there are lots, and get to the hard science and technology of testing implementation strategies, for which there are surprisingly few, and ultimately to scale-up, for which there are no current examples.
I just read a nice paper from a group in Germany that is experimenting with adding alkaline materials, mostly rock, to soil. The basic idea is that these added materials are of a type that react with CO2 to make carbonate minerals, which effectively traps the CO2 for 1000’s of years (at least) in the soil. This mimics natural weathering processes that are the master controller of CO2 levels in the atmosphere on geological timescales of 1,000s or tens of 1,000s of years. The hope is that by manipulating the system this natural process can be sped up -- a lot, maybe a hundred or even a thousand times.
The German group did quite a large experiment both in the field, and in greenhouses, testing dozens of different permutations of soil type and material addition type over several years. They found a number of approaches that didn’t work along with identifying some faulty assumptions they started with. They had success as well, some of this was also unexpected, for example using steel slag as the alkaline material. They come to the conclusion that it’s going to require a bunch of these kinds of larger scale experiments that test lots of permutations before we have enough information that we, and by ‘we’ I probably mean artificially intelligent algorithms, can guide the most effective methods to actually achieve meaningful CDR using the purposeful addition of alkaline materials to soil. I think this work does a nice job of pointing out the realities in terms of costs, time, and perseverance that are going to be required for any geoengineering approach.
With colleagues at Bigelow Laboratory, I am involved in a ‘blue carbon’ project assessing the efficacy of certain seaweed cultivation practices to capture carbon on long time scales. I don’t technically consider blue carbon geoengineering since much of it is based on restoration of degraded ecosystems like mangroves or saltmarshes, or regionally based mariculture (seaweed farming), which is what we are focused on. There are notions of growing massive amounts of seaweeds in the open ocean and sinking the biomass to the deep ocean floor, and that would be geoengineering, but that’s another story. At any rate, our findings, thus far, are also sobering in terms of ‘magic bullets’, but incrementally promising towards finding something real and sustainable. Again, this is real work and needs real money.
The point here is that developing meaningful CDR methods is not going to be easy, but will require concerted effort and substantial expense (although likely an infinitesimal amount compared to the cost of ‘doing nothing’).
Will we summon the will to do it? We are an incredibly adaptable species. Modern civilization put us on a rapid trajectory towards modifying Earth with little awareness of the consequences. We’ve since gained greater and greater awareness of what those changes have wrought. We can recognize the paths towards solutions. Were we to dedicate the effort required to geoengineer Earth to its current state (without awareness) to reverse geoengineering the planet (with some awareness) to a more climate stable state, we could certainly pull it off. Whether or not we’ve given ourselves enough time, especially given current intransigence, or have really put ourselves on a collision course with base planetary physical, chemical, and biological reality that doesn’t end well for human civilization as we currently know it? That is an open question.
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