Almost six decades later, “solar geoengineering” research has made scant headway.
It attracts less than 1% of climate science budgets, amid fears that tampering with the global thermostat could produce unexpected consequences - and distract from an overriding need for deep cuts in greenhouse gas emissions.
But governments are facing ever starker choices as global warming creeps towards 1.5 degrees Celsius (2.7 Fahrenheit) - a threshold set in the 2015 Paris Agreement, agreed by about 200 countries, to avert ever more damaging floods, droughts, wildfires and melting ice.
Such impacts are already surging with temperatures now just 1.1C above pre-industrial levels.
Last year, opposition from indigenous peoples forced the cancellation of an early, high-profile outdoor test of solar geoengineering technology by Harvard University.
The planned balloon flight over Sweden was designed as a first step toward releasing tiny reflective particles 20 km high in the atmosphere, to see if they could form a planetary haze mimicking a volcanic eruption.
Major eruptions - like that of Mount Pinatubo in the Philippines in 1991 - can cut global temperatures for more than a year, as an ashen mask circulates in the stratosphere.
This year, after the setback, backers of research into the risks and benefits of solar geoengineering are turning to diplomacy to advance their work.
“There is no question that in the public battle, if it is Harvard against indigenous peoples, we can’t proceed. That´s just a reality,” said David Keith, a professor of applied physics at the Harvard School of Engineering and Applied Sciences, who was involved in the balloon project, known as SCoPEx.
Harvard was considering alternative launch sites but Keith said “we also could kill the project. We really don’t know.”
Åsa Larsson-Blind, vice president of the Saami Council of reindeer herders, which led opposition to the test, sent an open letter to Harvard University in June urging an end to SCoPEx.
The group said the project violated indigenous peoples’ principles of living in harmony with nature. So far, “we haven’t heard back”, she said.
Janos Pasztor, executive director of the Carnegie Climate Governance Initiative, said the focus of solar geoengineering research efforts was shifting to winning broader backing for them.
He said he doubted there would be any outdoor experiments in the upper atmosphere this year.
“There is diplomatic work behind the scenes – you don’t see a lot of this on Twitter,” he said.
One aim of the push is to have solar geoengineering discussed for the first time by the UN General Assembly, the top UN policy making body, in a session starting in September 2023.
Pasztor said that the risks of geoengineering - such as a potential skewing of global weather patterns and monsoon rains - had to be judged against fast-worsening climate change impacts.
“Are the risks of a 2C (warmer) world worse than the risks” of geoengineering?, he asked.
That is a question expected to rise on the global diplomatic agenda.
FACING UP TO OVERSHOOT
The Paris Peace Forum, a non-governmental group, plans to appoint in coming weeks a commission of former government leaders to consider options if global temperatures overshoot the Paris Agreement’s goals.
The "Global Commission on Governing Risks from Climate Overshoot", to be chaired by Pascal Lamy, a former head of the World Trade Organization, will have 12-15 members and report back late next year.
Adrien Abecassis, who coordinates the work at the Paris Peace Forum, said the commission would consider both solar geoengineering and ways to extract carbon from the air, along with options such as more climate finance to help developing nations adapt to climate change.
Switzerland also is considering submitting a resolution to the UN Environment Assembly, which is likely to meet in April, to seek UN-level consideration of climate altering technologies and measures (CATM).
“Switzerland is of the view that an authoritative report by the UN system is key to enable an informed debate on CATM and their governance,” said Felix Wertli, head of the global affairs section of the Swiss Federal Office for the Environment, in an email.
Switzerland, backed by 10 other nations, withdrew a similar resolution at the UN Environment Assembly in 2019 after it failed to win sufficient support.
Some prominent scientists opposed to geoengineering say there is no need to advance consideration of such technologies as a way to address runaway climate change.
“It is dangerous to normalise solar geoengineering research,” Frank Biermann of Utrecht University wrote in the journal Nature last year, on behalf of 17 scientists, after the journal argued for more research.
Instead, “a global moratorium is needed”, he said.
Biermann and more than 60 climate scientists and governance experts on Monday launched an appeal for an "international non-use agreement on solar geoengineering", aimed at halting development and deployment of the technology.
Decarbonising economies needs to be the global priority, they argued, terming solar geoengineering neither ethical nor politically governable.
Lili Fuhr, head of international environmental policy at Germany's Heinrich Böll Foundation, which opposes geoengineering research, said “any next stage of research would basically take us down a slippery slope towards deployment. We know enough about its dangers that we can never use it.”
Also this year, the UN’s Intergovernmental Panel on Climate Change is expected to provide a scientific update on geoengineering research as part of a report due in early April about ways to combat climate change.
DEVELOPING WORLD VIEWS
Research on geoengineering options by scientists in developing nations is also growing.
Projects under a fund known as Decimals include how "solar radiation management" (SRM) - another term for solar geoengineering - could affect malaria rates in Bangladesh and dust storms in the Middle East.
A team led by Inés Camilloni of the University of Buenos Aires is looking at how SRM might affect rainfall in the basin of the La Plata river in South America, home to 160 million people.
“A key area of concern is the insufficient knowledge about the potential impacts at regional scale - and in this sense much more research is needed,” she said.
Andy Parker, who heads the Degrees Initiative and who helped create the Decimals project, said research into SRM in developing countries "is feasible, it is desirable.”
The Degrees Initiative, a UK non-profit group, was launched in 2010 as a partnership between the UK Royal Society, the Italy-based World Academy of Sciences, and the UN Environmental Defense Fund.
It says it wants to help developing nations evaluate the “controversial technology” of SRM.
Back in the 1960s, Parker said, UN President Johnson’s science advisors had little inkling that global warming would become so severe in the 21st century.
He predicted that the looming 1.5C threshold would force people to face up to what he called “the big question: what are our options if emissions cuts prove insufficient?”