The U.S. government office that oversees federally funded climate research has recommended studies into two areas of geoengineering research, marking the first time scientists in the executive branch have formally called for studies in the controversial field. The move, part of a climate science planning report sent today to Congress, will likely further normalize discussion of deliberate tinkering with the atmosphere to cool the planet, and of directly collecting carbon from the sky, both topics once verboten in the climate science community. Yet the new endorsement of geoengineering research comes amid deep uncertainty about the direction that climate research will take under the new administration of President-elect Donald Trump.

Geoengineering is discussed in just two paragraphs of the 119-page plan, which aims to set out a research roadmap through 2021. The planned research program would provide “insight into the science needed to understand potential pathways for climate intervention or geoengineering and the possible consequences of any such measures, both intended and unintended,” the report states. One near-term step researchers could take, it says, “is defining the scale and scope of observations and mod­eling capabilities necessary to detect the signal of any future field experiments” of geoengineering techniques, and ways “to evaluate their consequences. Such research would also define the smallest scale of intervention experiments that would yield meaningful scientific un­derstanding.”

The report also states that “[w]hile climate intervention cannot substitute for reducing greenhouse gas emissions and adapting to the changes in climate that occur, some types of deliberative climate intervention may someday be one of a portfolio of tools used in managing climate change.”

The U.S. Global Change Research Program (USGCRP), which produced the report, coordinates climate research across 13 departments and agencies. Currently, none expressly supports geoengineering research, though federal climate science officials have been quietly reviewing the idea for the entirety of the Obama administration. In 2009, in his first public interview after receiving Senate confirmation for the job of White House science adviser, John Holdren said he had discussed the controversial idea in his new position. A kerfuffle followed over whether the White House was “considering” geoengineering or not. In the aftermath, federal scientists rarely broached the topic publicly, though influential institutions like the Royal Society in the United Kingdom, the U.S. National Academies of Sciences, Engineering, and Medicine, and the House of Representatives science committee subsequently called for government-funded geoengineering research.

The agencies haven’t answered the call, as Science reported in 2015:

In recent years, scientists—often working on their own time—have published hundreds of theoretical or modeling papers on sun-blocking or carbon removal. But they’ve encountered numerous road blocks at funding agencies. When Douglas MacMartin of the California Institute of Technology in Pasadena approached the National Science Foundation for support on a modeling effort on [albedo modification], officials told him the work was too theoretical for the engineering division and too applied for the atmospheric science program. At [the Department of Energy], Columbia University physicist Peter Eisenberger’s proposed demonstration of a carbon sucking machine fared poorly since the department’s carbon-capture program focuses on coal, he says.

Of the two main geoengineering approaches—altering the albedo, or reflectivity, of Earth, and removing carbon from the atmosphere—there have been more actual experiments involving carbon removal, including work at several companies. A federal report released in November 2016 laid out a strategy for the United States to “deeply decarbonize” its economy by 2050, and said that developing carbon dioxide removal techniques “may be necessary in the long run to constrain global average temperature increases to well below 2°C.”

Excuse for inaction?

Some observers quietly worry that, under Trump, a new focus on climate engineering could become part of a justification for delaying government action to curb carbon emissions, with the reasoning that geoengineering technologies could later be used to remove carbon from the atmosphere, or prevent the warming effects of solar radiation.

Some types of deliberative climate intervention may someday be one of a portfolio of tools used in managing climate change. U.S. Global Change Research Program report

International relations professor Simon Nicholson, who co-runs the Forum for Climate Engineering Assessment at American University in Washington, D.C., says the new call for federal geoengineering research, in the last days of the Obama administration, is “ironic and extraordinarily sad.” Nicholson, like many researchers, has wanted federal research agencies to support more work in this area. Now, he fears that having “climate intervention on the radar of the new administration would be a distraction.” He’s reluctant to discuss the idea, he says. “The most important work to do with the new administration is to be sure they keep intact important international work on climate mitigation and adaptation.” Over the long term, he worries that climate skeptics in the policy world, after dismissing climate change as a risk in recent years, could later change positions and say it was real, embracing climate engineering “as this magic solution that could solve the problem.” (Many analysts believe reducing carbon emissions is first priority for preventing major climate disruptions.)

It’s far too early to know what the new administration will do regarding a relatively obscure issue such as geoengineering. Nicholson says that even if research agencies under Trump avoid research into geoengineering techniques such as albedo modification, the U.S. intelligence community might remain interested, especially in whether other countries are pursuing their own planetary cooling technologies, which could affect many nations.

The USGCRP report acknowledges this international aspect of the geoengineering challenge. “The need to understand the possibilities, limitations, and potential side effects of climate intervention becomes all the more apparent with the recognition that other countries or the private sector may decide to conduct intervention experiments independently from the U.S. Government,” the report says. Nicholson, however, is concerned that a focus on geoengineering purely as a security risk would be “a dangerous framing,” because it could promote secrecy around climate engineering studies. Solar geoengineering studies should remain in the open and under the purview of academic and government scientists, he says, in order to build trust with the public and the global community of nations.

*Update, 9 January, 10:40 a.m.: This story has been updated to provide further detail on the report's recommendations.

*Correction, 12 January, 1:47 p.m.: A previous version of this article misnamed Simon Nicholson. It has been corrected.