Exclusive: Climate Scientists Anticipate Solar Dimming Efforts by 2100

A study by top climate scientists projects that by the end of this century, humanity will undertake significant measures to block sunlight as a desperate effort to safeguard Earth’s population from the escalating impacts of climate change, as reported by New Scientist.

“Solar geoengineering is a troubling concept, yet it is becoming more appealing as global efforts to reduce greenhouse gas emissions fall short,” stated a respondent from Victoria University of Wellington, James Renwick.

According to the study, two-thirds of participants anticipate hazardous interventions will be employed to manage the atmosphere by the year 2100. Alarmingly, 52% believe these actions could be taken by irresponsible entities, including private firms, wealthy individuals, and nation-states, highlighting fears that attempts to cool the climate may proceed without comprehensive global governance to address decision-making or mitigate inherent risks.

“The potential for unintended consequences, political misuse, and abrupt climate impacts remains substantial,” a respondent remarked. Ines Camilloni of the University of Buenos Aires, Argentina, noted these concerns.

New Scientist invited around 800 climate researchers, contributors to the Intergovernmental Panel on Climate Change’s (IPCC) latest report, to participate in an anonymous online survey concerning solar geoengineering. The 120 respondents represented diverse academic fields from all continents, yielding one of the most extensive insights into the climate science community’s stance on solar geoengineering so far.

Since the 1960s, scientists have been exploring ways to enhance Earth’s albedo—the reflectivity of the planet—for a procedure known as solar geoengineering or solar radiation modification (SRM).

Cooling strategies might include the injection of particles into the upper atmosphere to reflect sunlight away from Earth, known as stratospheric aerosol injection. Another suggestion involves introducing salt particles into low-altitude ocean clouds, referred to as ocean cloud brightening (see “How does solar geoengineering operate?” below).

68% of respondents indicated that due to the global failure to reduce greenhouse gas emissions over the last decade, the likelihood of deploying such measures has increased. “It reflects a growing realization that we are not addressing climate change effectively,” noted Sean Fitzgerald from the Center for Climate Change Remediation at the University of Cambridge. “What options do we have? We may not prefer them, but if we disapprove of the current situation, we must consider alternatives.”

While consensus exists regarding the potential for solar geoengineering, experts disagree on the triggers for such drastic measures. Just over 20% of respondents believe these measures should be considered should global temperatures be on track to rise more than 2°C above pre-industrial levels, a scenario that is becoming increasingly likely with global warming surpassing the 1.5°C mark. Others argued that waiting for more extreme warming would be wiser, while over half felt current warming levels were insufficient to warrant serious consideration of atmospheric alteration.

Such actions could theoretically help lower global temperatures and provide time for emissions reductions, yet nearly all respondents recognized substantial risks associated with widespread implementation, including diminished motivation to cut emissions, disruption to vital agricultural rainfall patterns, and abrupt warming due to “termination shock” should these interventions cease.

The study further highlighted concerns regarding unilateral climate interventions by nations or individuals, with 81% of respondents agreeing that a new international treaty or framework is necessary to regulate all large-scale deployments, marking a significant consensus across the survey questions.

These findings reflect a cautious stance, according to Andy Parker from the Degrees Initiative. “This is a global technology. No nation can opt out of a geoengineered world. Similarly, no nation can choose to ignore a warmer world if geoengineering is rejected.”

Growing Interest in Geoengineering

New Scientist decided to undertake this research as interest in solar geoengineering grows amid escalating climate impacts. Hundreds of millions of dollars in funding are flowing into this area, with researchers presenting their findings at scientific forums, building a global research community. Earlier this year, the UK Government allocated £57 million in grants for solar geoengineering research via the Advanced Research and Inventions Agency (ARIA), supporting small-scale field experiments.

This represents a significant pivot for a field traditionally sidelined within climate science. Daniele Visioni has led numerous SRM modeling projects at Cornell University in New York. “This topic has transitioned from being loosely discussed by a small group of scholars to becoming a global issue.”

Just over one-third of the respondents from New Scientist‘s survey asserted that due to humanity’s ongoing struggle to cut emissions, they now support SRM research, albeit not necessarily its implementation. A notable 49% are in favor of conducting small-scale outdoor experiments to better understand the associated risks and benefits.

“There is growing acceptance of the necessity of SRM research,” Parker states, tying it directly to the increased pessimism surrounding climate change outcomes.

“Given that most surveyed experts believe solar radiation management is probable within the next century, we must collect comprehensive real-world data regarding the feasibility and potential impacts of these cooling strategies,” asserts Mark Symes, director of ARIA’s Climate Cooling Program.

However, support is by no means unanimous, with approximately 45% of respondents deeming this a contentious or taboo research area. A third opposed outdoor experimentation with any countermeasures, and 11% refrained from contributing to solar geoengineering studies to protect their professional reputation.

“Many of these climate scientists see that the initial vision of climate science—to heed the warnings of the Earth and reduce emissions—has failed,” according to Visioni.

Much hesitance regarding solar geoengineering stems from the multitude of potentially catastrophic risks associated with large-scale sunlight-reflecting efforts.

Almost all respondents noted that implementation might dampen motivation to reduce emissions as one of the most critical risks. Other significant threats included social and political unrest, severe disruptions to agriculture and food security, harm to delicate ecosystems, and public health crises. “Modifying the entire climate system through SRM is a considerable risk,” cautioned Shreekant Gupta at the Center for Social and Economic Progress in Delhi, India.

For instance, research indicates that enhancing cloud cooling effects over the Indian Ocean could mitigate droughts in North Africa while triggering droughts in East Africa. Additional studies suggest that aerosol injections into the stratosphere could damage the ozone layer and potentially reduce monsoon rainfall in parts of Africa by up to 20%.

However, the ambiguity of “unknown consequences” emerged as the most commonly mentioned risk. One survey participant pointed out that “human efforts to rectify damaged systems have often met with limited success.”

Three primary techniques for solar geoengineering include:

1. Stratospheric aerosol injection
This technique involves dispersing tiny liquid particles called aerosols from high-altitude aircraft to reflect sunlight. Over 60% of survey respondents identified this as the method most likely to be adopted.

2. Thinning of cirrus clouds
This method utilizes aerosols such as nitric acid to thin cirrus clouds, permitting more heat to escape into space. However, excessive aerosol spraying can thicken clouds and produce the opposite effect. Only a minority of respondents believed this method or land-based strategies for enhancing global albedo could be pursued.

3. Brightening ocean clouds
This approach involves spraying minute seawater droplets onto clouds, enhancing their brightness and increasing sunlight reflection. It was trialed in a small experiment in 2024 aimed at protecting the Great Barrier Reef. Approximately 16% of respondents felt this technique would likely be adopted.