Should we engineer the climate? A social scientist and natural scientist discuss

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Ekaterina Karpacheva/

This is an article from The Conversation’s Head to Head, a series in which academics from different disciplines chew over current debates. Let us know what else you’d like covered – all questions welcome. Details of how to contact us are at the end of the article.

Rob Bellamy: 2018 has been a year of unprecedented weather extremes around the world. From the hottest temperatures ever recorded in Japan to the largest wildfire in the history of California, the frequency and intensity of such events have been made much more likely by human-induced climate change. They form part of a longer-term trend – observed in the past and projected into the future – that may soon make nations desperate enough to consider engineering the world’s climate deliberately in order to counteract the risks of climate change.

Indeed, the spectre of climate engineering hung heavily over the recent United Nations climate conference in Katowice, COP24, having featured in several side events as negotiators agreed on how to implement the landmark 2015 Paris Agreement, but left many worried that it does not go far enough.

Matt Watson: Climate engineering – or geoengineering – is the purposeful intervention into the climate system to reduce the worst side effects of climate change. There are two broad types of engineering, greenhouse gas removal (GGR) and solar radiation management (or SRM). GGR focuses on removing anthropogenically emitted gases from the atmosphere, directly reducing the greenhouse effect. SRM, meanwhile, is the label given to a diverse mix of large-scale technology ideas for reflecting sunlight away from the Earth, thereby cooling it.

An engineered future?

RB: It’s increasingly looking like we may have to rely on a combination of such technologies in facing climate change. The authors of the recent IPCC report concluded that it is possible to limit global warming to no more than 1.5°C, but every single one of the pathways they envisaged that are consistent with this goal require the use of greenhouse gas removal, often on a vast scale. While these technologies vary in their levels of maturity, none are ready to be deployed yet – either for technical or social reasons or both.

If efforts to reduce greenhouse gas emissions by transitioning away from fossil fuels fail, or greenhouse gas removal technologies are not researched and deployed quickly enough, faster-acting SRM ideas may be needed to avoid so-called “climate emergencies”.

SRM ideas include installing mirrors in Earth’s orbit, growing crops that have been genetically modified to make them lighter, painting urban areas white, spraying clouds with salt to make them brighter, and paving mirrors over desert areas – all to reflect sunlight away. But by far the best known idea – and that which has, rightly or wrongly, received the most attention by natural and social scientists alike – is injecting reflective particles, such as sulphate aerosols, into the stratosphere, otherwise known as “stratospheric aerosol injection” or SAI.

MW: Despite researching it, I do not feel particularly positive about SRM (very few people do). But our direction of travel is towards a world where climate change will have significant impacts, particularly on those most vulnerable. If you accept the scientific evidence, it’s hard to argue against options that might reduce those impacts, no matter how extreme they appear.

Do you remember the film 127 Hours? It tells the (true) story of a young climber who, pinned under a boulder in the middle of nowhere, eventually ends up amputating his arm, without anaesthetic, with a pen knife. In the end, he had little choice. Circumstances dictate decisions. So if you believe climate change is going to be severe, you have no option but to research the options (I am not advocating deployment) as broadly as possible. Because there may well come a point in the future where it would be immoral not to intervene.

SRM using stratospheric aerosols has many potential issues but does have a comparison in nature – active volcanism – which can partially inform us about the scientific challenges, such as the dynamic response of the stratosphere. Very little research is currently being conducted, due to a challenging funding landscape. What is being done is at small scale (financially), is linked to other, more benign ideas, or is privately funded. This is hardly ideal.

A controversial idea

RB: But SAI is a particularly divisive idea for a reason. For example, as well as threatening to disrupt regional weather patterns, it, and the related idea of brightening clouds at sea, would require regular “top-ups” to maintain cooling effects. Because of this, both methods would suffer from the risk of a “termination effect”: where any cessation of cooling would result in a sudden rise in global temperature in line with the level of greenhouse gases in the atmosphere. If we hadn’t been reducing our greenhouse gas emissions in the background, this could be a very sharp rise indeed.

Read more:
Time is running out on climate change, but geoengineering has dangers of its own

Such ideas also raise concerns about governance. What if one powerful actor – be it a nation or a wealthy individual – could change the global climate at a whim? And even if there were an international programme, how could meaningful consent be obtained from those who would be affected by the technology? That’s everybody on Earth. What if some nations were harmed by the aerosol injections of others? Attributing liability would be greatly contentious in a world where you can no longer disentangle natural from artificial.

And who could be trusted to deliver such a programme? Your experience with the SPICE (Stratospheric Particle Injection for Climate Engineering) project shows that people are wary of private interests. There, it was concerns about a patent application that in part led to the scientists calling off a test of delivery hardware for SAI that would have seen the injection of water 1km above the ground via a pipe and tethered balloon.

MW: The technological risks, while vitally important, are not insurmountable. While non-trivial, there are existing technologies that could deliver material to the stratosphere.

Most researchers agree that the socio-political risks, such as you outline, outweigh the technological risks. One researcher remarked at a Royal Society meeting, in 2010: “We know that governments have failed to combat climate change, what are the chances of them safely implementing a less-optimal solution?”. This is a hard question to answer well. But in my experience, opponents to research never consider the risk of not researching these ideas.

The SPICE project is an example where scientists and engineers took the decision to call off part of an experiment. Despite what was reported, we did this of our own volition. It annoyed me greatly when others, including those who purported to provide oversight, claimed victory for the experiment not going ahead. This belies the amount of soul searching we undertook. I’m proud of the decisions we made, essentially unsupported, and in most people’s eyes it has added to scientists’ credibility.


Moral hazard

RB: Some people are also worried that the promise of large-scale climate engineering technologies might delay or distract us from reducing greenhouse gas emissions – a “moral hazard”. But this remains to be seen. There are good reasons to think that the promise (or threat) of SRM might even galvanise efforts to reduce greenhouse gas emissions.

MW: Yes, I think it’s at least as likely that the threat of SAI would prompt “positive” behaviour, towards a sustainable, greener future, than a “negative” behaviour pattern where we assume technology, currently imaginary, will solve our problems (in fact our grandchildren’s problems, in 50 years time).

RB: That said, the risks of a moral hazard may not be the same for all climate engineering ideas, or even all SRM ideas. It’s a shame that the specific idea of stratospheric aerosol injection is so frequently conflated with its parent category of SRM and climate engineering more generally. This leads people to tar all climate engineering ideas with the same brush, which is to the detriment of many other ideas that have so far raised relatively fewer societal concerns, such as more reflective settlements or grasslands on the SRM side of things, or virtually the entire category of greenhouse gas removal ideas. So we risk throwing the baby out with the bathwater.

MW: I agree with this – somewhat. It’s certainly true all techniques should be given the same amount of scrutiny based on evidence. Some techniques, however, often look benign but aren’t. Modifying crops to make them more reflective, brightening clouds, even planting trees all have potentially profound impacts at scale. I disagree a little in as much as we simply don’t know enough yet to say which technologies have the potential to reduce the impacts of climate change safely. This means we do need to be thinking about all of these ideas, but objectively.

Anyone that passionately backs a particular technology concerns me. If it could be conclusively proven that SAI did more harm than good, then we should stop researching it. All serious researchers in SAI would accept that outcome, and many are actively looking for showstoppers.

RB: I agree. But at present there is very little demand for research into SRM from governments and wider society. This needs to be addressed. And we need broad societal involvement in defining the tools – and terms – of such research, and indeed in tackling climate change more broadly.

Read more:
Why you need to get involved in the geoengineering debate – now

The question of governance

MW: Some people think that we should just be getting on with engineering the climate, whereas others feel even the idea of it should not even be discussed or researched. Most academics value governance, as a mechanism that allows freedom to explore ideas safely and there are very few serious researchers, if any, who push back against this.

A challenge, of course, is who governs the governors. There are strong feelings on both sides – scientists either must, or cannot, govern their own research, depending on your viewpoint. Personally, I’d like to see a broad, international body set up with the power to govern climate engineering research, especially when conducting outdoor experiments. And I think the hurdles to conducting these experiments should consider both the environmental and social impact, but should not be an impediment to safe, thoughtful research.

RB: There are more proposed frameworks for governance than you can shake a stick at. But there are two major problems with them. The first is that most of those frameworks treat all SRM ideas as though they were stratospheric aerosol injection, and call for international regulation. That might be fine for those technologies with risks that cross national boundaries, but for ideas like reflective settlements and grasslands, such heavy handed governance might not make sense. Such governance is also at odds with the bottom-up architecture of the Paris Agreement, which states that countries will make nationally determined efforts to tackle climate change.

Which leads us to the second problem: these frameworks have almost exclusively arisen from a very narrow set of viewpoints – either those of natural or social scientists. What we really need now is broad societal participation in defining what governance itself should look like.

MW: Yes. There are so many questions that need to be addressed. Who pays for delivery and development and, critically, any consequences? How is the global south enfranchised – they are least responsible, most vulnerable and, given current geopolitical frameworks, unlikely to have a strong say. What does climate engineering mean for our relationship with nature: will anything ever be “natural” again (whatever that is)?

All these questions must be considered against the situation where we continue to emit CO₂ and extant risks from climate change increase. That climate engineering is sub-optimal to a pristine, sustainably managed planet is hard to argue against. But we don’t live in such a world. And when considered against a +3°C world, I’d suggest the opposite is highly likely to be true.

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This blog was written by Dr Rob Bellamy, Presidential Fellow in Environment, University of Manchester and Dr Matthew Watson, Reader in Natural Hazards, University of Bristol Cabot Institute. This article is republished from The Conversation under a Creative Commons license. Read the original article.

Rob Bellamy
Matt Watson

Play stops rain: could ‘cloud seeding’ deliver perfect Wimbledon weather?

Image credit: Carine06, Wikimedia Commons

Wimbledon, 2026. Bright blue skies and a wonderful late afternoon sun lights up the lush green grass of centre court. Out strides the British number one and four-time winner, Andy Henman, to the cheers of the excitable, partisan crowd.

Somewhere nearby, at the headquarters of WeatherMod Inc, a group of technicians are busily checking data, confident that their efforts have worked. They have been in contact with two pilots who have just completed their spray sorties and are returning to land at Heathrow’s new third runway. Thanks to the delivery of 4kg of, in its pure form, a yellowish powder known as Silver Iodide (AgI) into clouds upwind of London, it is now raining over the Salisbury Plain, 100 miles away, and the rain predicted for later in SW19 is now 92% less likely.

This scenario probably sounds a little far-fetched, and not least the bit about the repeatedly successful home-grown tennis player. However, weather modification occurs more often than most people are aware. For example, as I wrote that first paragraph I genuinely didn’t realise that a Weather Modification Incorporated actually already exists in Fargo, North Dakota. They, and other companies like them have sprung up over the past few years promising to manage water for crops, clear fog and even protect wedding days from ill-timed hail.

But two questions need further investigation to consider the likelihood of the above scenario at Wimbledon: can we do it (that is, does it work) and should we do it? Neither, it turns out, are particularly easy to answer.

Changing the weather

In order to make rain several processes need to occur. First, small particles known as cloud condensation nuclei (CCN) are required onto which water can condense. Then these droplets need to grow to a size where they precipitate out of the cloud, finally falling where and when required.

In our hypothetical scenario we would therefore need to be able to either control or at least predict accurately the concentration of CCN, the rate at which droplets form, and the evaporation rates within the clouds. We’d also also need to have some handle on the rate and direction in which rain would fall.

Silver iodine dumped into a cloud attracts water, which turns into rain.
Smcnab386 / wiki, CC BY-SA

In reality, cloud seeding with AgI – the current default option – only really tackles the first of these processes, forming the condensation nuclei. Even if clouds are seeded, it is still a matter of debate as to whether they actually create much additional rain. While companies claim success, some scientists are more wary. Although other seeding agents (and methodologies) exist, it is worth noting that, in the case of AgI, the nature of the clouds into which the particles are injected will govern the outcome.

Seeding works best in clouds which have a pre-existing mixture of water droplets and ice, as this type of nucleation requires ice-crystals to form. Following the production of CCN we’d then need to be able to predict, through computer modelling, how small droplets will form into rain and eventually fall.

One of the major drawbacks of cloud seeding is a lack of proof that it works: given weather forecasting remains imperfect, how would you know what would have happened without intervention? The second part of the question is arguably even harder to approach. What are the ethics of removing water from one part of the world, even on a small scale, and moving it somewhere else? Is this “messing with nature” or “playing God”? Water is, after all, the most precious commodity on Earth.

Let’s assume for now that it is possible to alter local weather patterns and to prevent or cause rain. This could be used for both good and evil, and the potential for abuse is worth considering. While manipulating the weather as a weapon is now explicitly outlawed by the UN’s ENMOD treaty, there have been efforts to alter the outcome of conflict using cloud seeding.

‘Operation Popeye’: the US used cloud-seeding to extend the monsoon season during the Vietnam war, causing delays on the waterlogged Ho Chi Minh Trail.
manhhai, CC BY

Deliberate and accidental effects from commercial activity also seem possible. That dreamy, rain-free wedding ordered up by an anxious billionaire could easily ruin a school sports day in a nearby town.

The question of attribution is possibly the most challenging. Without any alternative outcomes to analyse, how can you really know what are the impacts from your actions. Some even say, quite incorrectly, that cloud seeding experiments caused floods, such as those that killed 35 people in the English village of Lynmouth in 1952. Expert opinion leans strongly against that idea being correct. Nonetheless, conspiracy theories persist. If, in our hypothetical Wimbledon scenario, bits of Wiltshire flooded, who would foot the bill?

It’s certainly possible in theory to prevent rain in one place by using cloud seeding to induce it in another, upwind. But there are huge challenges and the jury is still out about whether such efforts really work.

There are some very good causes, such as inducing rainfall in Sub-Saharan Africa during drought, where I would sanction intervention. For something as frivolous as a sporting event I feel differently. Just last weekend I played cricket for four hours in unrelenting drizzle (thanks Skip). While not a massively enjoyable experience it was at least familiar, and is part of the essence of both cricket and tennis. There’s some comfort in that.

The Conversation

This blog is by Matthew Watson, Reader in Natural Hazards at the University of Bristol.
This article was originally published on The Conversation. Read the original article.

Matthew Watson

Why we must Bridge the Gap

Much of the climate change of the past century has been caused by our burning of fossil fuels. And without a change in that fossil fuel use, continued climate change in the next century could have devastating impacts on our society. It is likely to bring increased risk and hazards associated with extreme weather events. Refugee crises could be caused by rising sea levels or droughts that make some nations uninhabitable. Climate change will also make our world a more uncertain place to live, whether that be uncertainty in future rainfall patterns, the magnitude of sea level rise or the response of global fisheries to ocean acidification.  This uncertainty is particularly problematic because it makes it so much harder for industry or nations to plan and thrive.  Or to grapple with the other great challenge facing humanity – securing food, water and energy for 7 billion people (and growing).  Because of this, most nations have agreed that global warming should be held below 2°C.

Flooding on Whiteladies Road, Bristol. Image credit Jim Freer

These climatic and environmental impacts will be felt in the South West of England.  We live in an interconnected world, such that drought in North America will raise the price of our food. The effects of ocean acidification on marine ecosystems and UK fisheries remain worryingly uncertain. The floods of last winter could have been a warning of life in a hotter and wetter world; moreover, it will only become harder to protect our lowlands from not only flooding but also salt water incursions as sea level rises.  The proposed Hinkley Point nuclear power station will have an installation, operating and decommissioning lifetime of over 100 years; what added risks will it face from the combination of more severe weather, storm surges and rising sea level?  Climate change affects us all – globally, nationally and locally in the 2015 European Green Capital.

That requires reductions in emissions over the next decade.  And it then requires cessation of all fossil fuel emissions in the subsequent decades.  The former has been the subject of most negotiations, including the recent discussions in Lima and likely those in Paris at the end of this year. The latter has yet to be addressed by any international treaty. And that is of deep concern because it is the cessation of all fossil fuel emissions that is most difficult but most necessary to achieve.  Carbon dioxide has a lifetime in the atmosphere of 1000s of years, such that slower emissions will only delay climate change.  That can be useful – if we must adapt to a changing world, having more time to do so will be beneficial. However, it is absolutely clear that emissions must stop if we are to meet our target of 2°C.  In fact, according to most climate models as well as the geological history of climate, emissions must stop if we are to keep total warming below 5°C.

In short, we cannot use the majority of our coal, gas and petroleum assets for energy.  They must stay buried.

Can we ‘geoengineer’ our way to alternative solution?  Not according to recent research. Last November, a Royal Society Meeting showcased the results of three UK Research Council Funded investigations of geoengineering feasibility and consequences. They collectively illustrated that geoengineering a response to climate change was at best complicated and at worst a recipe for disaster and widespread global conflict.  The most prominent geoengineering solution is to offset the greenhouse gas induced rise in global temperatures via the injection of stratospheric particles that reflect some of the solar energy arriving at Earth.  However, on the most basic level, a world with elevated CO2 levels and reflective particles in the atmosphere  is not the same as a world with 280 ppm of CO2 and a pristine atmosphere. To achieve the same average global temperature, some regions will be cooler and others warmer.  Rainfall patterns will differ: regional patterns of flood and drought will differ. Even if it could be done, who are the arbitrators of a geoengineered world?  The potential for conflict is profound.

In short, the deus ex machina of geoengineering our climate is neither a feasible nor a just option.  And again, the conclusion is that we cannot use most of our fossil fuels.

One might argue that we can adapt to climate change: why risk our economy now when we can adapt to the consequences of climate change later? Many assessments suggest that this is not the best economic approach, but I understand the gamble: be cautious with a fragile economy now and deal with consequences later.  This argument, however, ignores the vast inequity associated with climate change.  It is the future generations that will bear the cost of our inaction.  Moreover, it appears that the most vulnerable to climate change are the poorest – and those who consume the least fossil fuels.  Those of us who burn are not those who will pay.  Arguably then, we in the UK have a particular obligation to the poor of the world and of our own country, as well as to our children and grandchildren, to soon cease the use of our fossil fuels.

Energy is at the foundation of modern society and it has been the basis for magnificent human achievement over the past 150 years, but it is clear that obtaining energy by burning fossil fuels is warming our planet and acidifying our oceans.  The consequences for our climate, from extreme weather events to rising sea levels, is profound; even more worrying are the catastrophic risks that climate change poses for the food and water resources on which society depends.  It is now time for us to mature beyond the 19th and 20th century fossil-fuel derived energy to a renewable energy system of the 21st century that is sustainable for us and our planet.

We must bridge the gap.