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.
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.”
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.
"Philosophy begins in wonder" ~ Plato