Until recently, climate engineering was considered too risky to warrant serious attention, but as we edge closer to irreversible climate tipping points, that has begun to change. In April the first-ever tests of cloud brightening technology were carried out in the hope that it could save the Great Barrier Reef.
In these unusual times, it is easy for things to fly under the radar. The recent test of “cloud brightening” equipment off the coast of Australia in April is one such thing. Not only has it has not received the coverage it deserves, but where it has been reported, its true significance does not seem to have been grasped. This test is so very important because it acts as a proof-of-concept for a previously untested geoengineering technology, and arguably brings us one step closer to the acceptance and possible deployment of climate engineering as a weapon in the fight against climate change. I use the word weapon because, like wielding a double-edged sword, this technology gives us both enormous power and the ability to do great harm.
Let’s look at some definitions. Like the name suggests, climate engineering means the deliberate attempt to manipulate the climate to serve human purposes. Its first major use was by the US military during the Vietnam War, when they attempted to “seed” clouds to extend the monsoon season in the hope of disrupting North Vietnamese troop movements. Since then, climate engineering – or geoengineering – has become a general term for a number of techniques designed primarily to mitigate global warming. Some of these, such as carbon capture or stratospheric aerosol injection, you may have heard of.
Marine cloud brightening (MCB) is a type of solar radiation management (SRM) – a subcategory of geoengineering techniques which were developed with the aim of cooling the earth’s atmosphere by decreasing the absorption of sunlight. MCB works by spraying nano-sized sea salt crystals into the air, where they are carried by wind turbulence into low-altitude clouds. The salt crystals act as nuclei around which moisture can collect, thereby thickening and brightening the clouds so that they reflect more sunlight back into space.
It is important to note that geoengineering methods have never been deployed at scale, and even testing has been severely restricted due to the perceived risks.
What’s the Problem?
Unfortunately, when it comes to dealing with the climate crisis, there is no magic bullet. Among the gravest concerns around MCB is what it could do to the water cycle. Research using climate models have shown that cloud seeding in certain parts of the world can affect rainfall in other regions. Worryingly, one study showed that MCB near Namibia could even result in a reduction in rainfall over the Amazon. Its proponents argue that this should not dissuade us – we should use these models to cleverly plan where seeding takes place, not only avoiding unwanted side-effects but also creating positive ones.
The problem is that the climate is incredibly complex, and our understanding of it is far from complete, so climate scientists only have limited confidence in their ability to predict the outcomes of geoengineering. MCB could go drastically wrong, causing unforeseen droughts or severe monsoon seasons.
Another major concern is that it only deals with a symptom of the problem (i.e. warming), but may distract us from addressing its root causes (i.e. carbon emissions). This is highly problematic for a number of reasons. Firstly, CO2 is responsible for other environmental impacts beyond just heating the atmosphere – most notably ocean acidification, which poses a major threat to marine food chains that humans ultimately rely upon. Secondly, if MCB, by artificially delaying the global heating response merely provides a cover for irresponsible governments and businesses to continue to burn fossil fuels, it will be like sealing over a hole in an overstretched balloon but continuing to blow air into it. This is because CO2 sticks around for a long time. If for whatever reason (and there may be many – from geopolitical instability, to drastic unforeseen side-effects resulting from cloud brightening), the cloud seeding machines are abruptly turned off again, the balloon would burst. The world could face a rapid release of pent-up warming, which could trigger a rate of climate change unprecedented in Earth’s history. But even if the machines were to be kept on indefinitely, the effectiveness of the technique to compensate for ever-greater amounts of CO2-induced warming diminishes over time, as the amount of seeding required to create the next degree of brightening increases logarithmically, meaning that further brightening is likely at some point to become prohibitively difficult. NASA
These are just some of the concerns around MCB. Others include fears: that it could be weaponised; that its climate effects may not be measurable without irreversible large-scale deployment; and that it would be likely to have uneven impacts across the world, posing a huge challenge for global governance. Similar risks are involved with other geoengineering techniques.
It is not surprising, then, that until very recently geoengineering was considered to be too dangerous, and something best avoided. But as circumstances change, so does the debate around ‘acceptable’ levels of risk. The world is hurtling towards the precipice of runaway climate change at alarming speeds, and scientists have argued that we only have 11 years left to drastically curb greenhouse gas emissions, or face catastrophe. As a result, SRM and other strategies have increasing appeal and are quickly gaining traction among scientists and policymakers. The IPCC, the UNEP, and the US National Academy of Sciences have all begun to seriously consider research into, and the possible future deployment of, geoengineering.
Recent Cloud Seeding Trial off Australian Coast
The recent trial off the coast of Australia is the first time MCB technology has ever been tested in the real world. The project was funded as part of a $150 million government-backed program that is looking into experimental methods in a desperate attempt to save the Great Barrier Reef, which this year suffered its fifth and largest-ever major bleaching event (corals turn a ghostly white when they die, hence “bleaching” is synonymous with coral death). The test was only small-scale and limited in scope, but the first full-scale test to cool the surrounding ocean by brightening the clouds over the entire area of the reef is expected to take place within the next four years. ARC Centre of Excellence
Until recently, SRM strategies have been centred on tackling climate challenges on a global level, but the novelty of this approach is that it is focussed on a very specific area, with a very specific goal in mind, and for specific periods of time only (during summers months that experience marine heat waves). Daniel Harrison, the project leader, believes this means it will avoid the dangers associated with global geoengineering. “I don’t think [downstream effects] across significant distances are very likely from this. If the [conditions] were adverse enough… then you’d be aware of them fairly quickly. The atmospheric lifetime of the salt crystals is only a day or two, so you could stop it very quickly and see if conditions returned to normal.” That may be so, but critics fear that successful small-scale testing would legitimise geoengineering research and pave the way for much larger-scale implementation. While he is not naïve to this possibility, he is not too concerned. “It’s going to be quite challenging from an engineering feasibility point of view to even get this working at a large enough scale for the Great Barrier Reef, so I’m not at all convinced that it really is feasible to scale up cloud brightening to have a global impact.”
What about the worry that it could provide governments with an excuse not to cut carbon emissions? “I think we are passed that point,” he says. “Our modelling so clearly shows that if you don’t have very aggressive emissions reductions along with this technique, then there’s really very little point in doing it at all.” Even if we meet Paris-type goals, MCB would only buy the reef a couple of decades, he explains. “The real worry for us is that even if you do have those really aggressive emissions reductions, we’ve left it too late… The reef isn’t going to make it through to the other side without some additional assistance.” Business-as-usual, then, is not an option.
If the experiments over the Great Barrier Reef prove successful, we may be able to cautiously roll out MCB to include other targeted regional applications, such as protecting polar ice or Siberian permafrost. This approach has advantages over both global-geoengineering and no-geoengineering scenarios, because the risks of unwanted side-effects and problems of unequal international impacts are significantly lower, and because it could delay the onset of climate tipping points. In the case of permafrost, more than just dealing with a symptom of climate change, it could actually prevent the release of millions of tonnes of methane – a potent greenhouse gas.
What is not often mentioned in the public discourse is that, due to the delayed climate impacts of carbon, we could be committed to decades or even centuries of warming, even if we cut all emissions now. This implies that we may be unable to meet our Paris climate targets without carbon sequestration or some other form of climate engineering, especially if emissions continue to rise.
By plastering over the biggest cracks emerging in the stability of the global climate, MCB could buy us another 20 years or so to develop carbon capture technologies and scale up renewable energy deployment and other mitigation strategies. If we are lucky, and we use this extra time wisely, we might just be able to stop it breaking apart completely.