Are there urgent solutions that can stop climate change? Technological approaches to artificial climate modification have been discussed for some time under the terminology of geoengineering. However, most climate researchers are critical of these methods: the risks are high and the consequences for future generations will be immeasurable. Scientists in Bern have now explored the feasibility of halting the melting of the West Antarctic ice sheet by artificially dimming the sun.Their findings show that without decarbonization, artificial impacts will be ineffective and pose significant risks.
In a study just published in the journal Nature Climate Change, researchers led by Johannes Sutter from the Department of Climate and Environmental Physics (KUP) of the Institute of Physics of the University of Bern and the Oschger Center for Climate Research investigated whether the melting of the West Antarctic ice sheet can be prevented by artificially influencing solar radiation. Researchers also warn about unforeseen side effects of geoengineering.
Avoiding critical climate tipping points
"The window of opportunity to limit global temperature rise to less than 2 degrees is closing rapidly," said ice model expert Johannes Satter. "Therefore, it is possible that technological measures to influence the climate will be seriously considered in the future." This, he said, is why it is necessary to use theoretical models to study the impacts and risks of "solar radiation management." Solar radiation management (SRM) is a term used to describe various methods of blocking solar radiation to keep the Earth cooler.
An important reason for the growing interest in geoengineering is to avoid tipping points where the climate could change suddenly and irreversibly. These tipping points include the melting of the West Antarctic and Greenland ice sheets and the associated sea level rise of more than a meter. "Observations of the West Antarctic ice stream show that we are very close to the so-called tipping point, or have already passed it. Therefore, in our study we wanted to find out whether the ice sheet could theoretically be prevented from collapsing through solar radiation management," Johannes-Sutter explains.
Artificially dimming the sun
Specifically, Sutter and his colleagues studied if so-called aerosols -- suspended particles in gases -- introduced into the stratosphere managed to block solar radiation from Earth -- the equivalent of dimming the sun. To date, research has mainly focused on the global impacts of solar radiation management (SRM). Bern's study is the first to use ice model simulations to show what impact such measures would have on the Antarctic ice sheet. The study looked at the likely development of the ice sheet under different greenhouse gas scenarios in the future and came up with mixed results: If emissions continue unabated and particularly stringent controls are implemented by mid-century, the collapse of the West Antarctic Ice Sheet may be delayed to some extent but not prevented. Under moderate emissions scenarios, sustainable cooling mechanisms in Antarctica deployed by mid-century could prove to be an "effective tool" in slowing or even preventing ice sheet collapse.
According to model calculations, SRM will be most effective if implemented early and combined with ambitious climate mitigation measures. However, the study authors stress: "Our simulations suggest that the most effective way to prevent long-term collapse of the West Antarctic Ice Sheet is rapid decarbonization. The ice sheet has the best chance of long-term stability if greenhouse gas emissions are reduced to net zero without delay."
Possible side effects are difficult to study
But in real life, how should we imagine the sun dimming? According to Johannes Sutter, an entire fleet flying at extremely high altitudes must disperse millions of tons of aerosols in the stratosphere. However, this technological intervention in the climate must continue uninterrupted for centuries. If intervention were stopped as long as greenhouse gas concentrations in the atmosphere remained high, temperatures on Earth would quickly rise by several degrees.
Johannes Sutter points out that the consequences of such termination shocks are just one of the possible dangers of SRM. Potential side effects have not been fully studied, ranging from changes in monsoon regimes to changes in ocean and atmospheric circulation. Ocean acidification will also continue. Critics also warn of the political and social impact: the use of technologies such as dimming could lead to slower climate protection measures or even make them impossible to implement.
Thomas Stocker, professor of climate and environmental physics at the University of Bern and one of the co-authors of the study, said: "Geoengineering would be another global experiment and a potentially dangerous human intervention in the climate system, which should be prevented at all costs according to Article 2 of the United Nations Framework Convention on Climate Change."