Human modification of the atmosphere since the industrial revolution

Humanity has altered Earth’s systems (that is the ecosystems and the biodiversity they contain (including atmosphere, geosphere, hydrosphere, cryosphere and biosphere)) for millennia. The industrial revolution from the late eighteenth century saw these impacts ramp up with the intensive burning of fossil fuels to provide the almost unlimited energy that drove through technological revolutions in production of goods and services, food and medicine. Humanity’s impact on earth systems has accelerated almost exponentially since the early 1950s with the onset of technological innovation and marked increase in globalisation and co-operation—the Great Acceleration (Steffen et al. 2015). These rapid changes in earth systems which go beyond natural variability have led to the call for a new Epoch to be formally defined, the Anthropocene (Head et al. 2022), where human impact rivals geological forces on the earth. An Anthropocene atmosphere is characterised by rapid, often exponential increases in greenhouse gases (including carbon dioxide (CO2), methane (CH4) and nitrous oxides (NOx)), pollutants (including sulphur and heavy metals), and radioactive isotopes from atomic weapons testing (Dean et al. 2014). That is, we have radically altered the chemical composition of airspace that exists above us.

Humanity has altered the Earth’s atmosphere and the air that we breathe to such an extent that the concentrations of many naturally occurring greenhouse gases are at levels not seen since before the evolution of modern humans. For example, concentrations in atmospheric CO2 from fossil fuel burning and land-use change are the highest they have been for several millions of years (Monastersky 2013) and are largely responsible for driving recent global warming and ocean acidification. Increases in atmospheric pollutants, such as sulphur, lead and particulates, on the other hand, are strongly regional, especially in regards to environmental concerns such as acid rain and impacts on human health. Every year, air pollution from the burning of fossil fuels accounts for almost 7 million premature deaths alongside significant increases in associated non-communicable diseases.1

Acid rain results from the burning of fossils fuels and agriculture, both of which release huge amounts of sulphur dioxide (SO2) and nitrogen oxides (NOx), which are then converted in the atmosphere to sulphate and nitrate where they acidify rainfall. When sulphates and nitrates are transferred from the atmosphere to freshwater and terrestrial ecosystems (e.g. through acid rain), they cause biological damage in particular regions where the acids cannot be easily neutralised (Grennfelt et al. 2020). These are mainly regions where catchment geology contains low concentrations of calcium, including large parts of North America and Europe, areas that were responsible for causing the acid rain in the first place. However, as we will see below, increased atmospheric sulphates also cool the atmosphere, off-setting some of the global warming that would otherwise have accelerated temperatures even more quickly in recent decades (Brasseur and Roeckner 2005). Injection of sulphate aerosols into the atmosphere is, in fact, proposed as a key geoengineering approach to limit global warming, despite its potential environmental consequences.

Global warming acts as an essential backdrop to understand motivations towards weather and climate modifications, now and into the future. I consider both because they are tied together by historical technological innovation and legislation, and indeed share some similarities especially with regard to manipulating the air above us with chemicals, albeit in different parts of the atmosphere. The two approaches are distinct in terms of their scale, local versus regional/global, but as detailed below, recent weather modification programmes blur these spatial distinctions. Finally, given that the UN in 20222 declared that healthy environment (including air) is a human right, how we manipulate the air above us gives rise to new and continuing threats to this newly established human right and those associated with it.

Cloud-seeding and weather modification

Societies have long tried to influence local weather conditions, either to, for example, stimulate rain during drought (the “pluviculturalists”), or have a military impact on the outcome of war (Orville 1954). Cloud seeding to increase precipitation was established during a programme called Project Cirrus (1942–1948), funded by the US Army Signal Corps and the Office of Naval Research (Darak 2019). Potential applications of Cold War weather weaponization were outlined in an influential article by President Eisenhower’s weather advisor, Captain Howard Orville (Orville 1954). Writing in Collier’s magazine (Fig. 1), Orville outlined a two-staged approach, whereby (i) in the immediate future, weather forecasting needed to be improved through a network of radar stations and intensive computational data analyses, alongside (ii) a future goal of subsequently controlling weather through cloud-seeding techniques. Suggested military applications included: induce droughts so that an enemy’s agriculture would fail; induce flooding to disrupt transport networks and movement of armoured vehicles; increase cloud and rain cover to hamper aircraft-carrier operations. Orville even postulated that the other chief actor in the Cold War, Russia, would be at a disadvantage in the weaponization of weather because weather systems effectively moved west to east.

Fig. 1
figure 1

Front cover of Collier’s magazine, spotlighting article by Howard Orville on weather modification. Image version used supplied by Paleofuture

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During the 1960s, Project Skywater was funded by the National Science Foundation, to research weather modification using cloud seeding to increase water supplies in the USA. However, the optimism for weather control in the 1950s gave way to greater realisation of the limitations of what could be achieved due to the complexity of weather systems (Rogers and Gahan 2013). But while the aims of Project Skywater became more modest, private and military efforts to control weather continued. Perhaps the most infamous attempt to weaponize weather was the US Military’s Operation POPEYE (1967–1972) that undertook extensive seeding of the tops of very cold clouds in Laos, Vietnam and Cambodia with lead and silver iodide to extend summer monsoon rains to influence the outcome of the Vietnam War (Fleming 2007; Harper 2008). The American Weather Service covertly undertook 2,600 cloud seeding sorties and deployed over 47,000 silver iodide flares into the atmosphere (ibid). Silver iodide, when it is released into the atmosphere, causes water and condensation to cluster around it and that causes rainfall. This was done specifically to try to disrupt the transport networks, especially along the Ho Chi Minh Trail. Of course, it is difficult to target weather and so this intervention affected American camps as well. POPEYE was not the first time that the USA weaponized weather in SE Asia; the CIA were subsequently found responsible for trying to weaponize weather through cloud-seeding to suppress protests in south Vietnam by Buddhist monks in 1963 (Fleming 2007). Cloud seeding operations in SE Asia only ceased after being exposed by the New York Times in 1972 (Harper 2008).

After the USA renounced the use of weather modification techniques for hostile purposes in 1972, global discussions led to the UN’s Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (ENMOD) that came into force in 1978. Key to the Convention were for Party signatories under Article I “not to engage in military or any other hostile use of environmental modification techniques having widespread, long lasting or severe effects as a means of destruction, damage or injury to any other State Party”.3 The Convention, however, also specified that these techniques could be used for peaceful purposes to benefit humanity, which is why weather modification techniques are still being tested and applied in many countries, especially as droughts intensify in many regions of the world. For example, cloud seeding was undertaken in several drought-stricken regions of China in 2022 to create rainfall to offset the impact of one of the greatest droughts the country has experienced in modern times. Texas, USA, has a relatively long and well-documented history of cloud-seeding,4 with results suggesting almost 25% more rainfall in seeded storms compared to unseeded ones. Different technologies are being trialled elsewhere, for example in the UAE, where unmanned drones are being used to stimulate precipitation in this water-scarce country (Harrison et al. 2021).

One of the most ambitious and controversial weather modification programs, however, is China’s Tianhe Project or Sky River project,5 which aims to alter monsoon patterns over the Qinghai–Tibetan Plateau, such that concentrated atmospheric water vapour flows [or sky rivers; Wang et al. 2018)] are encouraged to flow northwards to the Yellow River basin region from the Yangtze River Basin, increasing Yellow River flow into drought-prone regions of northern China. Again, the principal technique is seeding clouds, though the method involves burning fuel in specially constructed chambers at altitudes of over 4000 m (Fig. 2). The smoke from the burning fuel released through upright chimneys attached to the chambers contains the silver iodide needed to stimulate precipitation. Although the Sky River Project is still under development, about 500 to 1,000 chambers have already been deployed and the plan is to build tens of thousands more (Hunchuck et al. 2021). This is a major operation, and what is still uncertain is the extent to which causing precipitation in one region will reduce precipitation in others. The project attempts to control longer term patterns of atmospheric water resources rather than just short-term weather events (Wang et al. 2018). Concern has been expressed, however (Bluemling et al. 2020), that the sheer scale of such regional schemes will contribute to the legitimisation for geoengineering approaches, i.e. the “…deliberate large-scale interventions in the Earth’s climate system” (Royal Society 2009) that I outline below.

Fig. 2
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Specially constructed chamber and chimney situated in the Tashkurgan region of the Northwest Tibetan Plateau as part of the China’s Tianhe or Sky River project. See Hunchuck et al. in the Avery Review (2021) for full details. Photo courtesy of Marco Ferrari and Elise Hunchuck

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Geoengineering and climate modification

We have known since the nineteenth century that the release of CO2 by the burning of fossil fuels will lead to an increase in atmospheric temperatures. The extent of disruption to environmental health and human society from weather and climate modification was detailed in a 1965 report by the US President’s Science Advisory Committee. A key point, amongst many, was the likelihood of increased destabilisation both in societal and ecological contexts. However, because of the UN Convention on Environmental Modification, the appetite for weather modification at large-scale was diminished (because military applications were explicitly banned) and the focus on geoengineering dropped away. Theoretical considerations as to how to mitigate against impacts from global warming were still being published, although they were few in number (e.g. Marchetti 19776). Since the late 1990s and successive publication of the Intergovernmental Panel on Climate Change (IPCC) reports, the evidence for anthropogenic global warming became more robust, as did the realisation that the implications of global warming on society and the environment would be extremely serious. It is against this backdrop that Nobel Prize winner Paul Crutzen wrote a seminal essay in 2006, asking if injection of sulphate particles (which act to cool the atmosphere because they are reflective, and scatter a small fraction of incoming sunlight back into space) into the stratosphere was a feasible solution to tackling climate change (Crutzen 2006). This provocation was highly influential, causing a rapid increase in studies specifically looking at the role that geoengineering may play in mitigating against future climate change (Boettcher and Schäfer (2017).

Here, I will briefly outline the two main approaches to climate geoengineering: radiative forcing management (e.g. solar geoengineering) and negative emission technologies (e.g. carbon dioxide removal). Solar geoengineering techniques range from the fantastical, such as installing mirrors in space that can reflect sunlight away and cause the earth to cool (Early 1989), to the more down-to-earth: painting buildings white in urban environments to reflect heat and light (Akbari et al. 2009). Crutzen’s proposition of injection of sulphate particulates into the atmosphere (stratospheric aerosol injection (SAI)) is a form of solar geoengineering. We saw above that sulphate pollution from burning of fossil fuels attenuates atmospheric warming caused by greenhouse gases. However, explosive volcanic eruptions also naturally inject millions of tonnes of sulphate into the stratosphere. It is estimated that SAI could cool global climate by as much as 2 °C (Barrett et al. 2014). SAI is one of the most widely modelled radiation management techniques, although its potential use is controversial; while these aerosols have the potential to cool the climate temporarily, they do not address the root of the problem, increasing greenhouse gas concentrations.

Many negative emission technologies (NETS), such as increasing carbon sequestration, are already in use and are fundamental to IPCC mitigation scenarios, i.e. to achieve emission reductions to keep future global warming from increasing above 1.5 °C (IPCC 2022). Techniques range from what are seen as ‘natural’ approaches, e.g. afforestation & deforestation, to technological solutions such as biomass energy with carbon capture and storage (BECCS). But while some of these techniques are more palatable in terms of policy making (e.g. planting more trees), they still come with their own threats, especially if scaled-up to reduce the huge amount of excess carbon already in our atmosphere (Oschlies and Klepper 2017). For example, covering large areas of land with new forest poses significant threats to biodiversity, food security and water quality. And while most modelling scenarios for reduction in atmospheric carbon involve the use of BECCS (Minx et al. 2018), the crops required to produce the energy would take a vast area of land conversion (possibly the size of Australia), posing real and significant threats to biodiversity and food security, and even carbon losses themselves (Harper et al. 2018).

Geoengineering: risks, governance and human rights

NETS aim to reduce greenhouse gases, the main cause of global warming, while solar geoengineering schemes such as SAI only aim to counteract the effects of global warming. SAI therefore does nothing to address the burning of fossil fuels nor changes in land use that contribute to increasing greenhouse gases in the atmosphere. Yet its appeal persists because it is seen as both an emergency measure to limit global heating and as a stop-gap until NETS schemes scaled-up are able to reduce atmospheric greenhouse gases (Barrett et al. 2014). However, very little is known about the environmental and health consequences of SAI should it be deployed (MacMartin et al. 2016). Here I will consider a few of the potential implications of deploying SAI as a climate engineering technique.

First, in the natural world, SAI from major volcanic eruptions not only acts to cool atmospheric temperatures for a year or two, but it also causes major changes to regional and global precipitation patterns (Fig. 3) (e.g. disruption of Asian monsoons (Iles et al. 2013)). Modelling large-scale deployment of SAI as a geoengineering tool results in temporary global cooling (Brovkin et al. 2009) but also the disruption of Asian and African monsoon systems (Robock et al. 2008), with significant reductions in Asian summer monsoon (Brovkin et al. 2009) threatening the livelihoods and food supply of billions of people.

Fig. 3
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The ecological effects of solar radiation management using sulphate aerosols. The schematic shows change in the drivers of ecosystem responses (blue) that are probable to arise from the use of sulphate aerosols, compared with not using sulphate aerosols, given current trends of increasing greenhouse gas concentrations, and the probable ecosystem responses (green). Drivers that are probable to change include temperature, precipitation, irradiance, monsoons and sulphate deposition. Ecosystem responses will be complex, with implications for food production, freshwater supplies, soil and water chemistry, and human health. They will also be spatially variable, creating both winners and losers, and uncertain, possibly causing large changes in ecosystems and in the availability of resources. Reprinted with permission from Barrett et al. (2014)

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Second, we know from monitoring volcanic eruptions that injection of sulphate particles into the stratosphere leads to ozone destruction, and SAI as a geoengineering tool would lead to the same effect (Fig. 3). While Crutzen (2006) suggests that SAI would only lead to modest ozone losses, losses are in reality likely to be higher, given the huge concentrations of aerosols that would now be needed annually to counteract ever increasing impact from anthropogenic greenhouse gases (Niemeier and Timmreck 2015). Increased penetration of UV radiation when ozone is depleted is likely to have an impact on human health (Carlson and Trisos 2018). Ecosystem damage from increased UV radiation (e.g. damage to plankton near ocean surfaces), would sit alongside terrestrial and freshwater damage from, for example, increased acid rain (Barrett et al. 2014) (Fig. 3).

Third, and this is important to re-emphasise, SAI does nothing to combat the underlying causes of global warming. Unchecked, increasing greenhouse gas emissions will continue to cause wide-scale ocean acidification, leading to major damage to marine ecosystems and human communities reliant on them (Doney et al. 2020). Moreover, should large-sale deployed SAI be stopped for any reason, e.g. due to war or other geopolitical/natural event, then atmospheric temperatures would rebound dramatically (as much as 5 °C in a few decades (Brovkin et al. 2009)). This would likely cause instability in global systems such as agriculture, and perhaps even stability of civilisation itself through ‘termination shock’ (Tang and Kemp 2021), and, although the risk of termination shock is contested, it should not be discounted (Parker and Irvine 2018).

It is clear that such large-scale climate engineering interventions pose huge risks to human society, which makes governance of geoengineering approaches at a global level fundamentally important. And although it is even been suggested that schemes such as SAI would violate the UN ENMOD convention because they would adversely affect regional climate patterns (Robock 2008), there are, as yet, no international or even national governance laws or initiatives that cover the emerging risk of SAI (Talberg et al. 2018; Grieger et al. 2019).

Alongside the uncertainties and concerns outlined above, the human rights implications of geoengineering in all its forms need to be urgently evaluated. For example, SAI has the potential to disrupt agriculture and water quality through changes in hydrological patterns (e.g. decline in monsoon intensity) and even increase the impacts of acid rain in some regions (Fig. 3), thereby impacting human rights related to food production and clean water. But although this perspective has focussed on SAI, techniques to reduce carbon in the atmosphere all require significant land-use changes which in one respect pose more immediate threats to human rights linked to access to food, safe water, and protection of biodiversity. In 2022, the Centre for International and Environmental Law issued a statement,7 requesting that the Advisory Committee of the Human Rights Council should report in 2023 on how new technologies related to climate change (including geoengineering) will impact on human rights. Concern that human rights are not being considered in the development and application of new technologies appears to be justified, especially given the lack of coherent national and international strategies to evaluate the risks inherent in all geoengineering approaches.

The proposed new human right to protect the freedom to live without physical or psychological threat from above could strengthen the case for protection for people and their environment from the threats of geoengineering (especially those who are most vulnerable or in the most vulnerable regions (Grief et al. 2018)). While weather modification to improve access to freshwater for drinking and agriculture is a clear benefit to local society, the threat to vulnerable populations elsewhere or ‘down-stream’ is poorly understood. The proposed new human right would allow considerations of citizens and displaced peoples from different legal jurisdictions to be taken into account as large-scale schemes are developed. As discussed by Grief (2020), we are still at relatively early stages of acknowledging the scale and long-term severity of psychological impacts on people affected by threats to airspace, e.g. through armed-conflict. Altering the airspace above us through technological means for long-term manipulation of the weather and possibly even climate may constitute such a threat in terms of psychological harm. Adopting a new human right could also act to strengthen the new human rights to access to food, safe water, and protection of biodiversity, by for example, ensuring that the concept of safe water includes quantity of water not being threatened in one region by manipulation of the weather/climate in another.

Notes

  1. 1.

    WHO (2022) https://www.who.int/news-room/fact-sheets/detail/household-air-pollution-and-health.

  2. 2.

    https://www.unep.org/news-and-stories/story/historic-move-un-declares-healthy-environment-human-right.

  3. 3.

    UN’s Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (ENMOD) https://www.un.org/disarmament/enmod/.

  4. 4.

    https://www.tdlr.texas.gov/weather/summary.htm.

  5. 5.

    https://averyreview.com/issues/53/prologue-to-the-sky-river.

  6. 6.

    This is also the first time geoengineering was used as a term to control impacts from climate change.

  7. 7.

    https://www.ciel.org/wp-content/uploads/2022/08/AC28_CIEL-statement.pdf.