Is manipulating the climate God’s work? Mankind, since Moses and ancient Cherokee tribes, has always tried to control the sun and the wind. Nowadays, thanks to advances in climatology and meteorology, controlling the climate has become a feasible option. This topic falls under the name of geoengineering, the science of weather and climate manipulation, which ranges from rain cannons to complex molecular dispersion into the atmosphere. Now a new wave of geoengineering technology could play a role in solving climate change: a panacea or a false solution?
We talked about this controversial issue with Ken Caldeira, a senior member of the Carnegie Institution’s Department of Global Ecology and a professor at Stanford’s Environmental Earth System Sciences department. Professor Caldeira has a wide-spectrum approach for analyzing the world’s climate systems. He studies the global carbon cycle; marine biogeochemistry and chemical oceanography, including ocean acidification and the atmosphere/ocean carbon cycle; land-cover and climate change; the long-term evolution of climate and geochemical cycles; and energy technology. He is one of the lead authors of the “State of the Carbon Cycle Report”, a study requested by the U.S. Congress.
«The scientific debate – Caldeira says – is increasingly focusing on climatic geoengineering. Research is being carried out to find technologies that reduce the amount of CO2 in the atmosphere (today there are over 400 ppm of CO2) and limit the effect of the changing climate».
Professor Calderia explained to us that today two main categories of geoengineering technologies exist: «The first one is called solar radiation management, which includes weather modification. It is based on the assumption that it is possible to reflect sunlight in the atmosphere or on the ground to avoid heat absorption and cool down the earth’s surface. We have learned from volcanic eruptions that putting particles in the stratosphere can reflect the sunlight away from the Earth and cool it rapidly. This has happened three times in the last Century».
Now the technologies are replicating this effect of solar radiation, for instance, the use of stratospheric sulfate aerosols disseminated by airplanes such as F15-C fighters that could create a strata of sulphate particulates. This would recreate an effect similar to the Piñatubo eruption that in 1991 injected large amounts of aerosol into the stratosphere – more than every eruption since the Krakatoa one in 1883. Over the following months, the aerosols formed a global layer of sulfuric acid haze. Global temperatures dropped by about 0.5 °C (0.9 °F), and ozone depletion temporarily increased substantially. In which way could solar radiation management serve mitigation strategies?
«Whenever climate change would become irreversible – Caldeira answers – climate models show that this could be a potentiality effective solution. If governments considered using stratospheric aerosols, they could be arranged in less than 2 years. A single plane, flying constantly, could disperse sufficient SO2»
What about the cost? Estimates show that it could cost over 10 billion dollars. «Something that can be afforded worldwide would allow us to see results in a couple of years. But we have to be careful: the effects on the ozone layer are unknown. Furthermore this solution won’t reduce the concentration of GHG in the atmosphere, nor fix ocean acidification related to the increase in CO2»
Other geoengineering technologies include cloud seeding (weather modification). This peculiar “cultivation” is used to modify the quantity and the type of precipitation that falls from clouds, by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical processes within the cloud. Chemicals include silver iodide and dry ice (solid carbon dioxide). Liquid propane, which expands into a gas, has also been used. The aim is to increase cloud coverage to limit solar radiation. However, application on a large-scale can be difficult.
Professor Caldeira explains that Cloud reflectivity modification could be more interesting: «Especially “Brightening marine clouds”, aimed to decrease absorption and increase reflectance above the ocean. The basic idea is that right before clouds produce rain, they become grey due to the thickness of the droplets: the solution is to inject tiny particles in the remote marine atmosphere, in order to produce smaller cloud droplets. Thus the cloud will appear white instead of gray, reflecting more sunlight back to space. Until now experiments have shown limited effects».
At Washington University, Professor Rob Wood has carried out a set of experiments to test cloud brightening presented by the Philosophical Transactions of the Royal Society. Wood has hypothesized special ships that can spray the atmosphere with a seawater nebulizer: this would form white clouds that would lower the earth’s albedo.
However, Caldeira is not convinced. «Other solutions exist, such as roof whitening and selecting brighter crops that reflect more sunlight, but the results are limited. ».
The second main category of geoengineering technologies is CO2 capture, which offers several options. «The simplest thing – Caldeira explains – is planting trees that absorb CO2 (carbon sink). There are also industrial systems of carbon capture from fossil fuel plants and storage underground (called CCS). Nowadays the main problem with this CCS technology is that it is too expensive».
However, there are other less known options. Ocean Fertilization is also known as iron seeding. This strategy employs iron to the upper ocean to stimulate a phytoplankton bloom. This process intends to enhance biological productivity, which can benefit the marine food chain. It is being investigated to see whether it is a successful means of facilitating increased carbon dioxide removal from the atmosphere (see J.A. Raven and P.G. Falkowski, 1999, “Oceanic Sinks for Atmospheric CO2″ Plant, Cell and Environment).
«Most people believe it works, even though it is not particularly effective and would require managing large areas of the ocean» observes the Stanford Professor. There are multiple risks, for instance harmful algal blooms could damage the food chain to anoxic areas (see Oschlies, A., W. Koeve, W. Rickels, e K. Rehdanz, 2010. Side effects and accounting aspects of hypothetical large-scale southern ocean iron fertilization” Biogeosciences Discuss). So far, planting trees and limiting soil consumption are indeed the most effective ways.
Until today nations have allowed limited testing. Precaution is the guiding principle since the effects are unknown. In 2010 the CBD, Convention on Biological Diversity (decision COP10 X/33) voted to outlaw geoengineering projects “until there is an adequate scientific basis on which to justify such activities and appropriate consideration of the associated risks for the environment and biodiversity and associated social, economic and cultural impacts”. The agreement exempted “small-scale scientific research studies”. In 2012 the CBD confirmed the decision, expecting further analysis based upon the IPPC’s Fifth Assessment Report (AR5) results.
Professor Caldeira says that, «Reflecting on geoengineering isn’t easy. In general, some approaches, such as putting particles into the atmosphere, would work well and wouldn’t be very expensive to put into place. But these approaches could work in a very limited sense: though they would cool the Earth, I think there are a lot of concerns related to the potential risks that can be associated with them».
The risks of at least two categories.
«First: direct environmental risk. For instance, what effect will these technologies have on the ozone layer or how will they affect ecosystems? Any time we start interfering on a large-scale with something as complicated as our planet, it is difficult to foresee the consequences. When we started using fossil fuel, we did not expect to see the planet warm up. Second: we have to deal with a wide array of social and political responses to geoengineering . For example, you can imagine a citizen saying: “ We have a quick and easy technological solution; let’s use it, so that we don’t need to do anything for GHG emissions.” But emissions continue to increase, leaving the stratosphere full of greenhouse gases. This is negative. The other concern is that we don’t live in a world where everyone can participate in decision making through democratic institution. So, imagine if one or more governments oppose to invest in geoengineering solutions, or are suspicious of them: this could lead to political or even military tension and eventually conflict. If governments start using these technologies and suddenly a devastating catastrophe happens, such as a drought, bad weather, or a terrible storm, people might blame geoengineering , even if there is no correlation, which could lead to social tension». Skepticism is understandable.
And what about the politics? It is quite unusual to listen to officials talking about the geoengineering issue.
«Politics are idle. I have been talking to several federal experts in the US (Caldeira belongs to the US delegation in climate negotiation, editor’s note), and politicians prefer not to talk about this issue because it too controversial. If politicians do not address this topic, they will not risk losing too many votes. But if they do address it, election camping adversaries could use it against them. My feeling is that politicians know that it is too risky to discuss this topic and they don’t want to be associated with it».
(Interview by Emanuele Bompan)
- Ken Caldeira personal page at Carnegie Institution Department of Global Ecology (Stanford University)
- Rethinking wedges – a paper published on Environmental Research Letters (Open Access)
- The Great Climate Experiment: How far can we push the planet? – a paper published in Scientific American
- Negative emissions: a special issue of Climatic Change, edited by M. Tavoni (CMCC) e R. Socolow (Princeton), read the post on the CMCC blog
- Carbon turnover rates in the One Tree Island reef: A 40-year perspective – Ken Caldeira in a video by Carnegie Institution’s Department of Global Ecology (Stanford University)