It is well known among climate researchers that an eruption of sulphate particles from Mount Pinatubo in the Philippines in 1991 resulted in a global cooling by about 0.5 degrees Celsius for the next two years… wait, did someone just say natural experiment?
If there’s one thing that unites (applied) economists, it’s their love for a good natural experiment. Nobel laureate David Card kicked off the craze by leveraging a mass emigration event (the Mariel Boatlift of 1980) to study the effect of immigration on the Miami labor market. These days, top publications typically need more than a clever identification strategy: ideally, the idea should stand a chance to be replicated at a larger scale (‘high voltage’ in John List’s recent book).
At first glance, exploiting volcanic eruption events appear to tick both boxes – it seems like a research design that could easily satisfy the causality police and the ‘high voltage’ criteria. The basic idea is that sulphate particles reflect more solar radiation back into space and mass production of such particles to shoot into the atmosphere is highly feasible. So, if there is an empirically verified way to wipe out two centuries of accumulated human-caused global warming, what is everyone waiting for? Why is such an approach not being discussed more in conversations regarding global warming and climate change? Is it time to google the timings of the other volcanic eruptions around the world and to use those as natural experiments in research?
Is geoengineering the solution to global warming?
The field that investigates climate solutions such as the use of sulphate particles is called geoengineering. It is an umbrella term that includes solutions such as shooting reflective particles in the atmosphere (i.e., managing solar radiation) and directly removing carbon dioxide from the atmosphere. A seminal essay in 2006 by Paul Crutzen, an atmospheric chemist who was awarded the Nobel Prize in Chemistry in 1995, did much to spur interest in geoengineering, once considered a taboo topic among researchers.
As highlighted by economists Gernot Wagner and Martin Weitzman in their 2015 book “Climate Shock”, while there were benefits of Mount Pinatubo’s eruption on global temperatures, it is not a panacea. Importantly, the eruption did nothing to counteract the direct effects of carbon pollution, the main cause of human-induced climate change. There are also uncertainties regarding the longer-term effects of introducing more sulphate particles into the atmosphere and the possible disruption to other environmental systems.
Controversies and uncertainties
Geoengineering remains a controversial topic with many people divided on the issue of whether engaging in climate interventions to manipulate the environment is a good idea. Some people believe that this would be a good way to reduce the effects of climate change, while others believe that it would have more negative consequences than positive ones. Yet others like Tim Flannery, Australian of the Year in 2007 for his work and advocacy on environmental issues, believe in a third way, geoengineering methods that are perceived as “natural”. They include planting trees or building artificial trees that capture CO2 from the air; producing and using biochar; farming CO2-absorbing seaweed; and constructing buildings from carbon-neutral cement capable of capturing CO2 from the air.
The issue of governance is a major difficulty for geoengineering. There is also the issue of moral hazard, the concern that the potential use of scientific strategies for global cooling might lead to increased carbon emissions, making the long-term climate problem even worse.
On the optimistic side, there are perhaps some parallels here with how the science of genetically modified crops helped increase global food production and has made inroads in partially tackling the issue of world hunger, despite health concerns about consuming them and their nutritious value.
Public awareness
One thing seems clear: the topic gets relatively little attention from the public. According to a 2019 Pew Research Center survey, 53 percent of Americans say they’ve heard nothing about cloud seeding and the idea of solar geoengineering is familiar to only a small share of the public – just 4 percent say they have heard or read a lot about it. The fact that a large proportion of the population is unaware of the severity of the climate crisis and the dire need for workable solutions is a clear indication that broader discussions are needed in the policy arena.
There is also no mention of geoengineering strategies in the recent 2021 report by the Intergovernmental Panel on Climate Change (IPCC). If a leading governing body stays mum on the topic, does this suggest there’s no clear path forward?
Nonetheless, based on the latest research, climate economist Gernot Wagner advocates in his recent book “Geoengineering: the Gamble” published in 2021 that we have to take the gamble, despite the risks and the fact that geoengineering is at best a technofix. The issue is now “not if, but when”.
With numerous other natural experiments like Mount Pinatubo’s eruption available for empirical investigation, I think there is a conceivable role for applied economists to contribute to this research agenda.
Wang-Sheng Lee
9 November 2022