Larsen C: Climate Engineering and Polar Ice Melt
This week, the Larsen C ice shelf broke away from Antarctica, setting a one trillion ton iceberg afloat in the Wedell Sea. While this event was natural and expected, scientists predict further calving events as temperatures rise, potentially unleashing several feet of sea level rise. We asked members of our Board of Advisors and other experts: Could proposed solar climate engineering technologies prevent or slow Arctic and Antarctic ice melt?
Tom Ackerman: “There are two perspectives from which this question can be addressed. On the short time scale, the answer is a pretty clear no. The loss of ice is a complex subject and we don’t know the answers in detail. We do know that it is not a simple function of global temperature but involves changes in atmospheric circulation and ocean warming. So, even deploying some sort of solar climate engineering now would likely take considerable time to stabilize the ice sheets.
On the longer time scale, we simply don’t know. The cryosphere has a long time scale and is asymmetric in terms of growth and decay. It is easy to melt ice (in a warming world) but takes much longer to grow it back because of the slow growth rates. The latter is especially true for land ice (Antarctica and Greenland) because you have to wait for snowfall accumulation and conversion to ice. Sea ice can grow more quickly but again has limitations because the ice insulates the ocean water from cooling so as the ice grows thicker it grows more slowly.
If this all sounds a bit hand wavy, it probably is. Unfortunately, there is a lot we don’t know about ice. Given that situation, it is hard to be definitive about the effects of solar climate engineering, about which we also know relatively little. I think the operative statement is that we simply do not know enough about solar climate engineering to have much confidence in the outcome of some action taken to stop ice loss in the Antarctic. We need to do the research so we have some idea of the potential outcomes.”
Thomas Ackerman is Executive Director of the Joint Institute for the Study of the Atmosphere and the Ocean (JISAO) at the University of Washington and a member of the FCEA Board of Advisors.
Doug MacMartin: “I think there is no question that (solar) climate engineering could be used to avoid further Arctic or Antarctic ice loss. What we don’t know is what the other impacts on the climate system would be, and we’re quite a long ways off from understanding our options well enough to make any informed judgment about the advisability of doing so. For the Antarctic in particular, the processes of ice loss are complicated, and dependent more on ocean than air temperatures, so a lot more modeling is needed to understand how much geoengineering would be required and what that might do elsewhere. And once an ice sheet collapses, geoengineering isn’t going to restore it.
There are two important take-aways from this. First is the need for research. We know far too little to consider solar geoengineering as an option today. Should something far more catastrophic happen in 10 or 20 years, the last thing we want is someone to make hasty decisions about deploying geoengineering without the knowledge to support that. Second, and even more important, is underscoring the importance of reducing our carbon emissions today, to reduce the probability of something catastrophic happening in the future. On the course we’re on right now, it’s pretty much guaranteed that sometime in the future (we just don’t know whether it is a few decades or a century) we’ll have destabilized enough of the Antarctic ice to raise sea levels by many metres, which would be catastrophic.
To clarify, I agree completely with Tom, with the caveat that I’m quite confident we can cool enough to halt further ice sheet loss in Antarctic – but that might require a sufficiently high forcing that it would be a really really bad idea for the rest of the climate. (That is, if we simply held global mean temperature constant by injecting aerosols into the stratosphere, I have no idea whether that would be enough to halt Antarctic ice loss – probably not, in fact almost certainly not, though it would mean less ice sheet loss than would occur if we didn’t do it.”
Douglas MacMartin is a Senior Research Associate and Senior Lecturer in Mechanical and Aerospace Engineering at Cornell University and a member of the FCEA Board of Advisors.
Jane Long: “Boy, do we need more research!”
Jane Long is former Dean of the Mackay School of Mines at University of Nevada, Reno and director of the Great Basin Center for Geothermal Energy and a member of the FCEA Board of Advisors.
Ken Caldeira: “Melting in Antarctica is strongly influenced by interactions involving the circulation of seawater, and its interaction with glacial ice, sea ice, surface winds and temperature, sunlight and so on. Many important interactions are occurring on small spatial scales that have not yet been successfully integrated into models simulating large-scale phenomena — and so the influence of various possible solar geoengineering deployments on Antarctic ice sheet dynamics remains largely unknown and unexplored.
The governing hypothesis is that if warming temperatures lead to ice melt, cooler temperatures are likely to help slow or even stop that melt.
It might turn out that it is effectively impossible to cool the water adjacent to ice shelves with solar geoengineering techniques. However, I would be surprised if that turns out to be the case. My expectation is that the primary factors limiting the amount cooling produced by solar geoengineering would be unintended consequences and sociopolitical acceptance.
We should be researching the potential effectiveness and unintended consequences of using solar geoengineering techniques to reduce the amount of damage caused by climate change. However, I would want to know a lot more about potential efficacy and unintended consequences, and understand how the solar geoengineering deployment fits into the broader spectrum of efforts undertaken to avoid climate damage, before I would want to consider using solar geoengineering approaches to protect Antarctica.”
Ken Caldeira is a climate scientist working for the Carnegie Institution for Science, Department of Global Ecology at Stanford University. He investigates issues related to climate, carbon, and energy systems. His primary tools are climate and the carbon cycle models, although he does field work related to ocean acidification.