Series of superimposed pictures of a person releasing a large white balloon, with mountains in the background.

NOAA is using balloons like this one (shown being released in a photographic time lapse) to measure the size and number of aerosols in the stratosphere.Credit: Patrick Cullis, CIRES/NOAA GML

The US government should launch a federal research programme to explore whether it’s feasible — or even wise — to artificially cool Earth by altering clouds or injecting particles into the atmosphere to reflect sunlight, according to a report released by the National Academies of Sciences, Engineering and Medicine (NASEM) last week. Two years in the making, the academies’ report is the most explicit call yet by an elite scientific body for a coordinated government research programme into solar geoengineering, aimed at exploring an emergency measure to blunt the climate crisis. Scientists say it comes at a politically opportune moment, with a climate-friendly US president, Joe Biden, now in office and bipartisan support for this type of research growing in Congress.

Released on 25 March, the report advises that the US government invest between US$100 million and $200 million over five years in solar-geoengineering research — including modelling and possibly field experiments, such as those to determine how aerosol particles injected into Earth’s stratosphere behave. Ideally in partnership with other nations, it says, the programme should advance basic environmental science, as well as address the ethics, governance and public perception of solar geoengineering. The report also recommends the creation of a comprehensive framework to oversee the research, including a code of conduct for scientists, an open-access registry for research proposals and results, and a process for granting permits for any outdoor experiments.

Although scientific agencies in the United States and abroad have funded solar-geoengineering research in the past, governments have shied away from launching formal programmes in the controversial field. In addition to fears that tinkering with Earth’s atmosphere could backfire in unpredictable ways, many environmentalists worry that focusing on geoengineering could reduce pressure on politicians — and the powerful fossil fuel-industry — to curb greenhouse-gas emissions. The report does not in any way advocate deploying the technology, but says research is needed to understand the options if the climate crisis becomes even more serious.

“Climate change is a genuine crisis, and we have been way too slow to get our act together,” says Christopher Field, an ecologist at Stanford University in California and co-chair of the committee that produced the report. “That’s part of the reason that we need to have a clear understanding of all of our options, including options that we would have not been willing to consider all that long ago.”

Shifting politics

Previous recommendations on the subject by elite scientific panels in the United States and abroad have gone largely unheeded. In 2009, the UK Royal Society issued a landmark report on solar geoengineering, and NASEM weighed in for the first time in 2015. But governments have yet to open the tap on funding, and most of the technical geoengineering research done so far has been limited to modelling studies.

What’s different today is the political atmosphere on Capitol Hill, says Kelly Wanser, executive director of SilverLining, a non-profit group based in Washington DC that advocates research into solar geoengineering and other climate-intervention technologies. Over the past two years, Congress has approved its first direct investments in the core climate science on clouds and stratospheric aerosols that is needed to understand solar geoengineering; the money has gone to the US National Oceanic and Atmospheric Administration (NOAA) and the US Department of Energy. Wanser says the discussion has been driven by an increased awareness of climate impacts, as well as national-security concerns and a sense that the United States needs to understand both the risks and the potential of such technologies.

“This is really about assessing risks,” she says. “There isn’t enough information today for policymakers to take a position.”

Moreover, former US president Donald Trump was against climate-mitigation efforts that negatively affected industry. With him out of the White House, many scientists say that Biden’s administration has the credibility to advance geoengineering research without rousing fears that doing so will merely displace regulations and other efforts to curb greenhouse gases, and give industry a free pass.

“Had the Trump administration tried to fund this research, the environmental-advocacy community would have rightly come down on them like a ton of bricks,” says David Keith, a physicist at Harvard University in Cambridge, Massachusetts, and co-leader of the Stratospheric Controlled Perturbation Experiment (SCoPEx), a front runner to be the first field experiment to test injections of aerosols into the stratosphere. Funding for the project comes from Harvard, as well as philanthropic sources.

Sustained investment

So far, the US Congress’s most significant investments in federal geoengineering research are at NOAA, which has received some $13 million over the past two years to advance basic-science studies of the stratosphere. A team of agency scientists has been deploying balloons that carry a lightweight, laser-based device to measure the size and quantity of aerosol particles in the stratosphere. And later this year, if things go according to plan, NOAA will conduct its first test flight aboard NASA’s WB-57 aircraft, which can carry additional research equipment into the stratosphere.

The researchers’ goal is to establish baseline information about what kinds of aerosol are already in the atmosphere, and to improve understanding of their origins — which include wildfires and volcanic eruptions. There has not yet been much in the way of sustained investment in this kind of stratospheric research, says David Fahey, an atmospheric scientist who heads NOAA’s chemical-sciences laboratory in Boulder, Colorado.

“That’s one of the troubles: the missions and the funding are not scaled to the problem,” says Fahey. A coordinated federal programme of the kind being advocated by NASEM could make all the difference when it comes to attracting talent and advancing research, he says. “It could create the impetus to invest, fly and bring on young scientists.”

For Sarah Doherty, an atmospheric physicist who manages the Marine Cloud Brightening Project at the University of Washington in Seattle, federal funding for solar-geoengineering research would bring something even more precious: advances in basic atmospheric and climate science. Finding money to pursue this kind of science has been difficult precisely because it gets entangled with moral and ethical quandaries posed by solar geoengineering. “It’s been a difficult area for the federal funding agencies to know how to handle,” she says.

Still, some scientists worry about the United States going it alone with a solar-geoengineering research programme, given the global ramifications of any efforts to alter Earth’s atmosphere. The NASEM report does call for the United States to promote international partnerships, and Keith says the country should do exactly that, if it moves forwards with the proposed strategy.

“That’s one of my biggest caveats: it would be unhealthy if this were only the United States,” he says. “International coordination is vitally important.”