LONDON - As climate change accelerates, the United Nations Environment Assembly will this week consider whether to start assessing, and setting rules on, technologies that could pull carbon out of the atmosphere or block some of the sun's warmth to cool the Earth.
Delegates at the week-long meeting in Nairobi will debate a proposal from Switzerland, backed by 10 other countries, to begin examining geoengineering technologies, which backers say could help fend off the worst impacts of runaway climate change.
If adopted, the proposal could lead to the highest-level examination yet of the controversial technologies, which have gained prominence as efforts to curb greenhouse gas emissions fall short.
"We need to have an understanding on the implications of using such technologies, and how they would be governed in the future," Siim Kiisler, Estonia's environment minister and president of the Nairobi meeting, told journalists on Monday.
"Just ignoring the issue does not help. We have to talk about it," he said.
Franz Xaver Perrez, Switzerland's environmental ambassador and head of its delegation in Nairobi, said his nation had concerns that sun-dimming technology, in particular, could have "a tremendous negative impact."
Nonetheless, "we should not be guided by concerns, but have a better understanding of the situation first", he told the Thomson Reuters Foundation, noting that "we might need multilateral control of these technologies."
Opponents say the technologies present huge potential risks to people and nature, and could undermine efforts to cut emissions, not least because many are backed by fossil-fuel interests.
"These technologies provide a perfect excuse for delaying action or weakening our current emissions reduction targets," warned Carroll Muffett, president of the Washington-based Center for International Environmental Law, in a telephone interview.
Rapidly slashing emissions - by switching to greener power, preserving forests and similar measures - remains the cheapest and safest way to fend off worsening droughts, floods, storms and other impacts of global warming, he said.
But research is moving ahead fast on two groups of alternative technologies to curb climate change, as emissions continue to rise.
One set aims to suck heat-trapping carbon out of the atmosphere and store it underground, or use it in other ways.
The other focuses on cooling the planet by blocking some of the sun's energy, through measures such as high-altitude planes that spray reflective sulphur particles into the stratosphere.
In a paper published on Monday in the journal Nature Climate Change, scientists modeling the use of solar geoengineering technology said limited deployment - to halve expected warming over the next century, rather than stop it entirely - could dramatically lessen risks from stronger tropical cyclones, for instance.
Earlier modeling of solar geoengineering to avert all projected warming flagged the possibility of changes in water availability, sparking fears the technology could shift monsoons, and create "winners" and "losers."
Opponents of the technology have suggested it could even be "weaponized," with a water-short country deploying the technology to improve its rainfall at the expense of neighbors.
But the new modeling suggests no region would see dramatic shifts with lighter use of the technology, although the scientists noted the results were based on an "idealized" study.
Lead author Peter Irvine, a postdoctoral research fellow at Harvard University, said solar management would need to work hand-in-hand with reducing emissions, and could not "replace mitigation."
David Keith, the leader of a team focused on solar geoengineering research at Harvard and a co-author of the study, said the modeling suggested "geoengineering could enable surprisingly uniform benefits" if used with mitigation efforts.
Option to ban
A high-profile report released by climate scientists last October, exploring how to hold global warming to 1.5 degrees Celsius above pre-industrial times, the most ambitious goal set by governments in the 2015 Paris Agreement, specifically did not consider the use of solar geoengineering.
It said the technology was untested, had "substantial" risks, and would not address the problem of oceans becoming more acidic as they absorb growing amounts of carbon dioxide.
Muffett said bodies such as the U.N. Environment Assembly, if they did begin exploring geoengineering technologies, should leave open the possibility of banning them entirely, as progress on their development could boost pressure to deploy them.
The assembly also should make sure any panel assessing the technologies included representatives of poorer countries and indigenous groups, while excluding those who held patents on the technologies or stood to profit from them, he said.
This week's meeting is not the first effort to explore and potentially regulate the emerging technologies.
Member nations of the Convention on Biological Diversity in 2010 set a non-binding moratorium on the use of geoengineering technologies, though agreed to permit research on them.
And an ocean pollution convention has banned the dumping of iron into the sea to boost uptake of carbon dioxide by algae, while also allowing research on the topic.
Janos Pasztor, executive director of the Carnegie Climate Geoengineering Governance Initiative, which hopes to spur effective governance of the emerging technologies, described the U.N. Environment Assembly's focus on them as a positive step.
"What is needed is governments to engage and start a serious conversation about these issues," he said.
If approved, the Swiss-backed proposal being presented in Nairobi this week would require U.N. Environment to analyze the technologies and report by August 2020 on how they could be governed and used at scale, among other things.