In the past month, three unusually strong hurricanes devastated parts of the Caribbean, Texas, and Florida. Hurricane Harvey came ashore near Houston, Texas, dropping over 40 inches of rain and displacing over 30,000 people. Hurricane Irma, with winds peaking at 185 miles per hour, devastated several Caribbean islands. Hurricane Maria hit Puerto Rico as a Category 4 storm, leaving the entire island without power. There are some indications that climate change, and the warmer oceans it causes, is driving stronger, more devastating hurricanes, carrying more rain.
There have long been fringe proposals for human interventions to weaken hurricanes, born out of the hope for some control over these natural disasters. While early research efforts were abandoned, the possibility of hurricane modification has reemerged as the climate engineering research field grows. Some researchers talk about using proposed climate engineering technologies, such as those that might brighten marine clouds, or those that might increase the albedo of the earth’s upper atmosphere by scattering a small amount of incoming sunlight using introduced aerosols, to steer or weaken storms, or to reduce the ingredients for the formation of these storms
Climate engineering technologies are not yet real in the world. Most of the conversation about research into such technologies has been broadly about responding to the phenomenon of climate change, specifically global warming. An increased focus on impacts is starting to emerge in some of the literature. People are beginning to consider the concept of climate engineering technologies for use in countering specific climate change impacts, for instance; to end a drought, prevent a famine, slow Arctic ice loss, among others.
The feasibility of this idea, using climate engineering to reduce the frequency or intensity of damaging hurricanes, or to steer a storm once it is formed, is not clear. Further, critics argue that discussing the possibility of hurricane modification a distraction from the emergency response, coastal resilience, and climate mitigation policies that are most likely to prevent damage from hurricanes.
With this in mind, we asked members of our Board of Advisors, made up of physical and social scientists, to comment on the question “Could climate engineering technologies be used to slow or weaken hurricanes? Is this a research question worth proposing or a distraction?”
This is what they told us:
Janos Pasztor, Executive Director, Carnegie Climate Geoengineering Governance Initiative
Not being an earth-atmosphere-system scientist, I cannot answer your question with any authority. Nevertheless, a few thoughts may be relevant:
Mark Lawrence, Managing Scientific Director, Institute for Advanced Sustainability Studies
First, modification of individual hurricanes would fall under the topic of weather modification, rather than climate geoengineering; and second, there is not nearly as much research on [hurricane modification] as on the possible effects of climate geoengineering on slowing the melting of ice sheets.
It actually has a very long history, going back 70 years to 1947 and the Project Cirrus experiment with Hurricane King – you can see Jim Fleming’s book (Chapter 5) for an overview of that. But that went awry in the public eye, and since then the research was mostly very tentative.
Some of the best work on the topic has been published by Kelly Klima, who works with Granger Morgen. Particularly interesting in the context of the FCEA is likely to be the work on public perception and policy perspectives:
Klima, K., Bruine de Bruin, W., Morgan, M. G. and Grossmann, I. (2012), “Public Perceptions of Hurricane Modification. Risk Analysis,” 32: 1194–1206. doi: 10.1111/j.1539 6924.2011.01717.x http://onlinelibrary.wiley.com/wol1/doi/10.1111/j.1539-6924.2011.01717.x/full
“Thoughts on whether the government should steer a tropical cyclone if it could,” Kelly Klima & M. Granger Morgan, Journal of Risk Research Vol. 15 , Iss. 8,2012 http://www.tandfonline.com/doi/abs/10.1080/13669877.2012.686054
“Hurricane Modification and Adaptation in Miami-Dade County, Florida” Kelly Klima, Ning Lin, Kerry Emanuel, M. Granger Morgan, and Iris Grossmann. Environmental Science & Technology 2012 46 (2), 636-642 DOI: 10.1021/es202640p http://pubs.acs.org/doi/abs/10.1021/es202640p
Doug MacMartin, Cornell University
Of course, any of the global climate modification ideas will cool sea surface temperature and thus will reverse trends in hurricane strength that result from global warming; that could return the statistics back to where they were, but that is quite different from modifying an individual event.
I would only add that if you could somehow steer a hurricane (no idea if that is technically possible), rather than simply weakening it, that has much more profound moral complications that worry me enough that I don’t even want to explore that technically; it’s quite a different problem in every respect from managing climate.
Tom Ackerman, University of Washington
The answer to this question is yes, no, or maybe depending on how the question is qualified. The consensus of the meteorological community is that hurricane intensity will increase during this century as sea surface temperature rises. (See, for example, https://www.gfdl.noaa.gov/global-warming-and-hurricanes/.) Hurricanes draw their energy from the ocean and warmer waters provide an increase in both temperature and moisture content of the tropical atmosphere, which leads to storm intensification. There is less certainty about whether the number of hurricanes will increase. Thus, in some general sense, cooling the surface of the ocean through solar climate engineering will weaken hurricane intensity. This at best, however, addresses a global population of hurricanes (and typhoons and cyclones) rather than an individual event.
If one asks the question in terms of a single, existing hurricane such as Hurricane Harvey, which just devastated the Texas Gulf Coast, the answer is most probably no. Harvey was a Category 4 storm with winds in excess of 130 mph. The forces involved in such a storm are enormous due to the tremendous amount of kinetic energy generated through the transfer of heat from the ocean surface and subsequent condensation in the hurricane. The forces that we can affect through climate engineering are tiny by comparison and unlikely to have any significant impact on an already formed and propagating tropical storm/hurricane. This is certainly true for solar climate engineering, but I think it is also true for other suggested techniques such as bringing cooler water to the surface of the ocean using pumping of some kind. There are published reports on such work.
The answer of maybe comes from a somewhat different scenario. Solar climate engineering can potentially affect climate by applying small forces over extended periods of time. So, one could propose to reduce the solar energy to the Gulf of Mexico starting in early summer and extending through the fall. If such a plan had been in place this year, then the sea surface temperatures in the Gulf might have been reduced by a few degrees, which would, in turn, have reduced the intensity and magnitude of Harvey. The potential pitfalls of such a plan are obvious. The decision to mitigate temperatures would have to be made long before the appearance of any tropical storm heading into the Gulf. The technique to be used, presumably marine cloud brightening (since it is the only way to apply a local forcing) may or may not be effective in the summertime Gulf given the air quality and lack of low clouds. It is unclear whether one could predict the amount of cooling in the Gulf if MCB were applied and what impact that would have had. Harvey would still have been a devastating hurricane even if it were a Category 2 (or 1) storm. And, one would also need to understand the impact of cooling on marine life and the circulation of the Gulf.
An even more complex question arises if one considers the fact that the greatest damage in Texas due to Harvey will most likely be associated with the rainfall rather than the intensity. The intense rainfall was due to a complicated interplay between the intensity of the hurricane, its path, and the fact that it stalled over the coast with part of it still over the water so the storm dynamics could access the heat and moisture of the Gulf. Whether cooler water would have affected any of these factors other than the wind intensity is unclear.
Given our current limited understanding of how climate engineering processes and whether their effects can be adequately predicted, it seems that we would be better advised to develop a general research program that explores climate engineering processes through both experiments and computer simulations than to develop a narrow focus trying to address a specific application. Such a narrow focus is likely to distort the development of the broader science and direct activities into paths that may lead to dead ends. Conversely, it would be helpful to have a program that allowed exploration of applications to complex phenomena in order to broaden our understanding of possible uses.