Our Burning Planet


Day Zero or Day Sulphur – new Cape Town study re-opens controversy on human manipulation of the world’s climate 

Space satellite orbiting the earth. Elements of this image furnished by NASA.

Local and international climate scientists think it may be possible to significantly reduce the risk of another Day Zero water crisis in Cape Town by… wait for it… pumping clouds of sulphur dioxide particles high up into the sky to manipulate the world’s climate artificially.

This may sound like a crazy science fiction movie plot, but reputable scientists from across the world are busy examining the impacts of such proposals. And now climate analysts at the University of Cape Town and colleagues in France, US and Norway, suggest that the heat of the sun can in theory be dimmed artificially by “injecting” large volumes of sulphur dioxide into the stratosphere (about 10-50km above the Earth’s surface) to reflect solar radiation back into space, thereby altering climate patterns and potentially counteracting the global warming crisis.

The scientists used computer models to simulate what might happen to Cape Town’s climate and rainfall patterns if global governments – or some of them – opt to deploy controversial and as yet untested “geo-engineering” strategies such as Solar Radiation Management (SRM).

Geo-engineering (which involves a variety of proposals to manipulate the Earth’s complex natural processes to slow the rate of global warming) is a highly contentious topic because of the risk of large-scale unintended effects – and the fact that this technological approach dodges the need to drive down industrial emissions and other greenhouse gases heating the atmosphere.

Before exploring those issues further, however, the headline conclusion of new research published today, noon SAST Wednesday, November 18 is that injecting large volumes of sulphur into the sky above the tropics would help to reduce the risk of future “Day Zero” level droughts in Cape Town by as much as 90% in the future. 

See the full paper here

Dr Romaric Odoulami, a postdoctoral climate scientist at the University of Cape Town’s African Climate and Development Initiative, told Daily Maverick that there were still several uncertainties about the consequences of climate experiments and there could also be “winners and losers” if sulphur dioxide injection was adopted.

Dr Romaric Odoulami, a post-doctoral climate researcher at the University of Cape Town, is lead author of the new study.  Photo:Supplied

In simpler terms, he explained that solar manipulation could lead to more rainfall in some places, and significantly less rainfall than normal in other places.

Odoulami, lead author of the study in Environmental Research Letters, said that while SRM could potentially preserve current winter rainfall patterns on a local scale around Cape Town, other researchers suggest it could also lead to less rainfall over some parts of Southern and Western Africa.

A separate research paper published earlier this year on similar sulphate geoengineering simulations suggests that it could boost rainfall over parts of the Sahel region – but also lead to a simultaneous and significant decrease in summer monsoon rains in parts of West Africa.

In that study, the authors also referred to a series of projects which indicate that sulphate aerosol injection (into the Northern Hemisphere only) could induce drought in the Sahel, whereas sulphate aerosol injection (in only the Southern Hemisphere) may lead to a significant increase in the Sahel vegetation productivity. Such experiments might also change the position of the Inter tropical Convergence Zone (ITCZ) and cause shifts in rainfall.

Odoulami’s paper attempts to address some of the uncertainties on the impact of sulphur injection on drought and water availability at the very local scale through the lens of the Cape Town Day Zero drought. It does not explain the complex manner in which such technology might alter wind, atmospheric pressure or hydrological cycles around South Africa, although reducing the volume of heat which reaches the Earth’s surface could theoretically reduce water evaporation from dams and the soil.

Last year, Odoulami and Dr Izidine Pinto of the UCT Climate System Analysis Group, published a separate study on potential impacts for Sub-Saharan Africa. It notes that there is still a considerable lack of knowledge about the potential impacts of geo-engineering at the regional scale.

While it seemed likely that sufficiently large injections of sulphur could limit future surface temperature increases or even reduce global surface temperatures, this would not directly reverse the impact of past and ongoing greenhouse gas emissions.

Overall, they concluded that such technologies could lead to less extreme temperature and rainfall anomalies than in a world without solar radiation management. However, up to 40% of Africa’s land – including parts of West and Southern Africa – would not experience any benefits in terms of rainfall.

Odoulami did not respond directly to questions on whether scientists were opening a potential Pandora’s Box by pursuing such studies on the impacts of climate manipulation. However, he stressed that very little research had been done so far on potential impacts for Africa, one of the regions expected to suffer inordinately from human-induced global warming.

“We would like to be able to inform (African) policymakers when it comes to making climate-related decisions . . . so that they have access to the right information on what the impacts may be.”


An expert report from the UK Royal Society says a range of geoengineering proposals have already been made – including plans to inject large volumes of sulphur particles in the stratosphere to reflect solar radiation away from the Earth. However, the expert report says the subject remains bedevilled by much doubt and confusion. “Some schemes are manifestly far-fetched; others are more credible, and are being investigated by reputable scientists; some are being promoted over-optimistically, ”it said. Photo:Supplied


.Photo: Supplied


Photo: Supplied

Dr Mark New, a fellow UCT scientist and co-author of the latest study on Day Zero droughts around Cape Town, said: “We already know the best way to avoid global warming and its impacts: It is to cut greenhouse gas emissions radically. But we also have to understand other options and their wider implications. In case emission cuts prove insufficient to avoid climate damages, and this study is an important step forward for African involvement in SRM research.”

However, this “Plan B” fallback strategy, sometimes hailed as the only quick and relatively cheap way to drive down rising temperatures, has nevertheless drawn strong criticism from several quarters, including the Canadian-based Action Group on Erosion, Technology and Concentration (ETC Group).

ETC, which monitors the impact of emerging technologies and multinational corporate strategies on biodiversity, agriculture and human rights in Africa, Asia and Latin America, has called on governments to consider a complete ban on any forms of SRM.

In a briefing paper distributed at the United Nations Environment Assembly in Nairobi last year, the group said this technology posed significant risks to human food security and the environment in Africa and urged government to strengthen the de facto moratorium adopted in 2010 on this technology by the UN Convention on Biological Diversity.

There are several other geo-engineering proposals to reflect more light back into space, including spreading rubberised micro-bubbles into the sea; using drones to spray dust and ice onto the clouds or growing genetically-modified crops with shiny leaves.

Other geo-engineering proposals include dumping thousands of tons of iron filings or urea into the sea to stimulate phytoplankton growth to absorb carbon, or burying vast quantities of industrial carbon dioxide and other greenhouses deep beneath the sea or in underground geological bunkers.

The ETC group believes the precautionary approach should be strengthened and governments should also consider a total ban on SRM “to prevent a group of powerful countries from continuing to develop and eventually deploying geoengineering with catastrophic consequences for the continent”.

“The climate system is complex and highly nonlinear in its behaviour, and perturbing one element of it in this way can lead to unforeseen changes.”

For example, selective injections in parts of the world could ward off heat waves in one country, but precipitate storms in a neighbouring nation.

“Blasting sulphates into the stratosphere, enhancing albedo (sun reflection) over oceans or land, and other SRM techniques will not reduce carbon dioxide concentrations. SRM would merely postpone the impacts for as long as the technology continued to be deployed.”

Quite apart from concerns around atmospheric sulphur injections leading to acid rain or an increase in health-damaging air pollution, some researchers say that if SRM was halted after a few years, it could result in very abrupt and more extreme climate change.

No data is provided in the recent Cape Town study on the volumes of sulphur dioxide used in the computer modelling experiments, but some previous modelling experiments have proposed that 45 Tg (45 million metric tons) of sulphur dioxide would be needed to maintain current global temperatures if the world does not cut greenhouse gas emissions dramatically.

The recent research on Cape Town drought impacts has been sponsored by the DECIMALS Fund, which supports the Solar Radiation Management Governance Initiative (SRMGI) which describes itself as the world’s first international SRM research fund, and the first aimed at researchers from the Global South.

“It supports eight teams of scientists as they model how SRM could affect their regions. In time, it is hoped this will transform the international conversation around SRM geoengineering. The DECIMALS research projects will put developing countries and emerging economies at the centre of efforts to understand its local risks and benefits, and will kick-start further conversations about the ethics, governance and politics of engineering the climate.”

It says the fund is administered by The World Academy of Sciences which distributes more than $1-million in research grants every year to support science across the developing world.

According to the SMRGI website, this theoretical approach to reducing some of the impacts of climate change by reflecting a small amount of inbound sunlight back out into space is still in the early stages of research, but acknowledges that it has become a controversial topic. 

“It is clear that SRM has the potential to be very helpful or very damaging for those people and species most threatened by climate change, but it is very unclear what its full effects would be,” says SMRGI project director Andy Parker.

“SRM would not directly reduce concentrations of greenhouse gases, and therefore numerous expert reports have concluded that it could never be a complete solution to global warming and does not represent a substitute for mitigation of greenhouse gas emissions.

“However, they have also concluded that it might be able to reduce some climate risks to which Earth is already committed, though even for this more limited purpose, whether it can be net positive to humanity and the environment is unclear.”

Parker led the production of the Royal Society’s Geo-engineering the climate report and is currently an Honorary Senior Research Fellow at the University of Bristol, UK. DM.



Comments - Please in order to comment.

  • Glyn Morgan says:

    Potentially a great idea! Or maybe not a great idea at all! BUT I have the answer to global warming! This is IT! Reduce the number of unwanted children born every year, reduce the average birth-rate and the population density. Then land area per capita will increase, poverty will decrease, productivity will increase, pollution will decrease, per capita income will increase and the need for more infrastructure will decrease. The world will be a better place for all mankind. Without the risk of unforseen consiquences of science gone wrong. Or grow trees. Read this book from 2005. The Golden Toad is Dead, published by lulu.com A badly written book but it has a great slant!

  • Franz Dullaart says:

    More “Burning Planet” nonsense and scientist hubris.

  • Ben van der Bank says:

    Sulpher dioxide injections, must be Trump.

    • Don Mingay says:

      Could somebody please remind me why a fortune is spent on coal fired stations to prevent emissions of sulphur into the atmosphere. I seem to remember that acid rain was one considered problem but there are there not also several more health issues?

      • Harro von Blottnitz says:

        Sulphur dioxide in the stratosphere is what this article is about – here it impacts the earth’s radiation balance by reflecting more incoming energy out. In the troposphere, sulphur dioxide indeed has several negative environmental consequences.

  • John Cartwright says:

    The problem with this approach is that it is using – or planning to use – advanced hi-tech measures to resolve a problem (climate change) which has to a large extent been brought about by the uncontrolled application of hi-tech measures, mostly involving fossil fuels. We’ve seen enough ‘unintended consequences’ of our recklessness already, thanks.

  • Rodney Weidemann says:

    So let me get this straight: In order to prevent climate change, these guys are proposing that we actively change the climate?
    Have we learned nothing from the disaster that occurred a century ago in Yellowstone Park, when one of its top predators – wolves – were hunted to extinction because of a perceived threat to humans and to livestock in the surrounding areas?
    without wolves, coyotes ran rampant, and the elk population exploded, overgrazing willows and aspens. Without those trees, songbirds began to decline, beavers could no longer build their dams and riverbanks started to erode. Without beaver dams and the shade from trees and other plants, water temperatures were too high for cold-water fish.
    And here we are talking about the elimination of one species from a single ecosystem – that sounds far less risky than injecting chemicals into atmosphere, where we have to potential to impact the incredibly more complex global climate system in ways we cannot understand yet!!

  • Don Mingay says:

    I tried to be gentle in my first reply through a rather innocuous question to which I knew the answer. However, more plainly, this is regurgitating a long dead topic, dismissed by global awareness as a result of the unknown consequences long ago and for many good reasons. In this release I find nothing new to warrant starting up this pie in the sky concept once again.

  • Rory Short says:

    The whole earth systems are complex in their interactions beyond anything that we humans can currently comprehend or successfully model. So what are we to do about global warming? I have been a practicing Quaker for nigh on 60 years now and I know from experience that, permeating the physical universe, there is a benign Spirit, which is conscious like ourselves, that wants the best for it’s creation(s). Now, because we too are conscious and can thus have an effect on the Universe, it needs to guide us into doing what is best for us and by natural extension what is best for the rest of the Universe. But first, because we are conscious, we have to choose to follow it’s guidance. The greater number of individuals who seek and action the Spirit’s guidance the more certain we will be of escaping from the abyss we are blindly creating for ourselves.

  • Carsten Rasch says:

    Ludicrous suggestion… science and our capitalist system has effed up our world beyond repair, but wait! we can fix it by pumping poisonous gasses into the sky! This is Plan B to save our planet which consists of countries which collectively cannot even make a simple decision to clean up our air, lest they get voted out at the next election by the growing cohort of climate denialists. The other option is to find faith super fast and start praying. Ironically, our best option is a benevolent dictator (not Trump. Or Bolsanero, Putin, Modi or any of the present “kragape”) who will just make the necessary changes regardless of public opinion.

  • mike muller says:

    This idea is not as controversial as is made out. It was developed by (amongst others) Paul Crutzen, who was awarded a Nobel Prize for fixing the ozone hole that was threatening to greatly increase melanoma cancers globally. He proposed it not as a solution but as a holding action while greedy people argued about who would lose and who would gain from global climate change mitigation programmes.

    So it is good to see that UCT doing the research. The problem faced by SSAfrica is that we are one of the regions likely suffer most from the impacts of warming. In some other regions (think northern Europe, Russia, Canada) it is suggested that there may be gains from increased agricultural productivity etc. while Africa burns.

    If we can demonstrate that regionally driven geoengineering could be beneficially undertaken, it becomes a negotiating chip in the larger global climate discussions.

    We already know that solar radiation management works on a grand scale: Nature provided lessons from volcanic explosions that had substantial cooling effects; while decreases in manmade industrial emissions have been shown to accelerate warming. What Crutzen and his colleagues pointed out was that targeted delivery of relatively small quantities of a reflectant like SO2 could significantly reduce warming.


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