It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Thursday, January 29, 2026
Cleaner ship fuel changed clouds, but not their climate balance
After maritime shipping emissions were sharply reduced following a mandated switch in fuels, Utah scientists sprang into action to see how the change would affect cloud formation over North Atlantic
'Ship tracks' above the northern Pacific Ocean. These patterns are produced when fine particles from ship exhaust float into a moist layer of atmosphere. The particles seed new clouds or attract water from existing cloud particles. These tracks virtually disappeared after 2020 when shipping vessels switched to cleaner fuelds. Image taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard NASA’s Aqua satellite on July 3, 2010.
Credit: NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team.
To reduce air pollution associated with ocean transport, the International Maritime Organization tightened restrictions on sulfur content in ship fuel resulting in an 80% reduction in emissions by 2020. That shift created an inadvertent real-world experiment in how man-made aerosols influence cloud formation over the ocean.
A team of atmospheric scientists led by University of Utah professor Gerald “Jay” Mace used this rare opportunity to explore the impact of reduced emissions on marine boundary layer clouds over the eastern North Atlantic. They discovered clouds’ internal structure changed, featuring fewer, but larger droplets of water. Yet the clouds’ reflectivity of sunlight surprisingly remained unchanged.
“You couldn't plan this type of thing,” Mace said. “The shipping in the entire world went from one thing to another, almost like the flick of a switch, and it just so happened that that had a known effect on clouds globally. Doing a natural experiment like this, I don't think it could ever happen again, unless we went back to sulfur fuels.”
With fewer sulfur particles in the air, there were approximately 15% fewer cloud condensation nuclei, the tiny particles on which cloud droplets form, according to the findings reported in the journal ACP Letters.
“There's a certain amount of water available to condense, and it condenses on whatever the local aerosols are,” Mace said. In the more polluted clouds in the higer sulfur fuel, “the clouds in the ship tracks then had a lot more aerosol to condense onto. So that available water had been divvied up into a higher number of droplets that are smaller.”
Now the clouds’ microphysics has been altered thanks to the sudden reduction in sulfur particles, a finding that Mace expected and that others had found.
Mace’s team examined observational data collected around the Azores, the archipelago in the Atlantic nearly 900 miles west of Portugal, for two-year periods immediately before and after the fuel regulations took effect in 2020. This study area, situated amidst busy shipping lanes between Europe and North America, was selected because it is the location of the Atmospheric Radiation Measurement program’s (ARM) Eastern North Atlantic site, operated by the U.S. Department of Energy.
Mace initiated this research project to determine whether the reduction in shipping emissions, resulting from the new fuel requirements, would accelerate climate change by changing cloud properties over the Atlantic. Some scientists theorized that might happen, but Mace’s study found that not to be the case.
It turned out that the clouds after the fuel change held more total water overall, which balanced out changes in droplet size and maintained cloud solar reflectivity, known as albedo. Had the albedo of Atlantic clouds reduced, they would have reflected less of the sun’s heat back into space, thereby warming the climate.
These counterintuitive findings prompted his team to look at observations recorded by two of NASA’s orbiting Earth-observing instruments, MODIS and CERES.
The satellite imagery confirmed there was little to no change in cloud reflectivity and optical depth in the region around the Azores.
“When we looked at the water paths, they had shifted just enough, just in the right way to completely offset the radiative effect of this change,” Mace said. “Somehow the climate system had adjusted itself so that the radiative effect of these clouds maintained balance.”
Mace noted that precipitation did increase slightly as expected with the increase in droplet size, but that increase came in the form of light drizzle. There was an actual decrease in heavy rainfall, enough to explain the change in the liquid water path the team observed.
So it is likely changes in the amount of cloud cover over the region were more closely linked to shifts in weather patterns than to aerosol changes, suggesting multiple factors govern how clouds behave.
Mace is hesitant to suggest his findings apply globally.
“It's a regional finding, and I can't generalize it without a lot more data,” he said. “What we can conclude from this study is that the climate system is able to adjust itself in ways that can be counterintuitive and simple arguments often need to be considered more carefully."
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The study appeared Jan. 22 under the title, “Impact on Cloud Properties of Reduced-Sulphur Shipping Fuel in the Eastern North Atlantic,” in the journal ACP Letters, published by the European Geosciences Union. Co-authors include Sally Benson, Peter Gombert, and Tiffany Smallwood of the University of Utah’s Department of Atmospheric Sciences. Funding came from the National Science Foundation, NASA and the U.S. Department of Energy.
The risks of climate change to human wellbeing are serious. Appropriate mitigation and adaptation require structural changes that are only likely to occur as a result of collective climate action. Danielle Goldwert, Madalina Vlasceanu, and colleagues explored what causes people to take collective climate action in a megastudy capable of directly comparing 17 behavioral interventions. The 17 interventions were derived from an open call to behavioral scientists and advocacy experts and included various framings and arguments such as emphasizing the benefits of climate action on health and jobs or highlighting successful examples of collective action. Over 31,000 US residents, recruited through Connect by Cloud Research, an online data collection platform, were given one of the 17 interventions—or no intervention, for the control group. Participants were then given the opportunity to engage in collective climate action of various kinds. One of the most effective interventions was highlighting successful examples of collective action and emphasizing collective action’s emotional benefits to participants. This intervention increased public awareness advocacy, such as committing to attend a climate march, by ten percentage points and increased political advocacy, such as supporting political campaigns of climate-friendly representatives, by six percentage points. Appealing to the purity and sacredness of “America’s pristine nature” increased financial advocacy by six percentage points. The purity intervention was even efficacious among Republican participants. By contrast, drawing attention to the personal toll of climate disruptions was most effective in increasing personal lifestyle change commitments such as promising to fly less or eat less beef. Framing pro-environmental behavior as patriotic was the intervention most effective for nudging participants to real action: writing a letter to a representative that was actually delivered. According to the authors, the findings can help guide those who wish to galvanize the public to collective climate action.
Journal
PNAS Nexus
Article Title
A megastudy of behavioral interventions to catalyze public, political, and financial climate advocacy
Article Publication Date
27-Jan-2026
How to motivate collective action on climate
One of the most effective ways to move individuals to act together on climate involves showing them how past collective actions have delivered structural change, a new study finds
What does it take to spur individuals to act as a group with a shared purpose on climate change? According to a new Stanford-led study, the key is to show them how collective actions on climate have made a difference and often generate good vibes for participants.
A decade after nearly 200 world leaders agreed in Paris to limit climate change, solar power has become the fastest-growing source of new electricity and dozens of countries have cut emissions while growing their economies. Globally, emissions from burning fossil fuels – the largest contributor to human-caused climate change – have slowed but not declined.
“Structural change is truly what’s needed, but you can’t get structural change without individuals demanding it,” said Madalina Vlasceanu, an assistant professor of environmental social sciences in the Stanford Doerr School of Sustainability and senior author of the study, which appears Jan. 27 in the journal PNAS Nexus.
Vlasceanu and her team recruited more than 30,000 U.S. residents to test 17 different psychology-backed interventions intended to encourage people to join a collective climate action, such as participating in a public demonstration or writing to a representative. The interventions featured videos, images, text, and interactive elements, such as prompts to write a short reflection.
The top intervention provided examples of past collective efforts on climate that have influenced public policy, showed a short video conveying the energy at climate marches, and invited participants to recall or imagine forming friendships through climate action. The intervention closed with a message that joining collective actions can boost happiness and build social connections.
“People really engage in collective action if they are made to feel that it will matter, that it will have an impact and create structural change, while also benefiting them personally,” said lead study author Danielle Goldwert, a PhD student at New York University.
Optimism over anger
After the intervention phase, participants had the opportunity to take or commit to any of three action types. The researchers grouped actions such as signing up for a climate organization’s newsletter, sharing a video calling for collective climate action, or committing to attend climate-related demonstrations into a “public awareness” bucket. They grouped political actions such as signing a petition, writing a letter to a representative, or committing to support “climate-friendly” politicians into a second bucket. Finally, they grouped financial actions such as donating to climate organizations or committing to divest from banks that invest in fossil fuels.
The most effective intervention overall – combining evidence of impact with social and emotional benefits – increased willingness to take public awareness actions by 30% and political actions by nearly 14%. Moral framing around purity and sanctity, emphasizing preservation of America’s pristine places and sacred national monuments, raised financial advocacy by about 13%. Interventions that relied on negative emotions like guilt and anger were less effective on average.
The researchers were surprised to find virtually no change in participants’ commitments to taking collective climate action when interventions emphasized co-benefits of addressing climate change, such as how reducing pollution improves human health or investing in renewable energy leads to economic growth.
“It feels intuitive that co-benefits should motivate people – why wouldn’t we solve climate change if it’s also going to solve health care and the economy? But we found null results in all categories when using this strategy,” Vlasceanu said.
Motivating long-term change
In previous research, Vlasceanu has examined what motivates people to take individual climate actions, such as recycling or eating less red meat. While there is some overlap, the primary motivating factors for individual actions center around how difficult they are to implement. The new study provides evidence that collective climate action may be more motivated by knowledge of how effective the action can be.
“When you want to do something about climate and it’s personal, you primarily do the things that are easy,” Vlasceanu said. “When you want to do something about climate and it’s collective, you definitely want to do the thing that will work.”
The interventions were fairly short – 10-15 minutes each – so the researchers expect they will only create short-term changes in participant behavior. But Vlasceanu and her team are working on creating and testing longer interventions. With support from the Doerr School of Sustainability’s Discovery Grant program, Vlasceanu and co-author Sara Constantino, assistant professor of environmental social sciences, are developing a documentary based on the principles of the most successful interventions. They intend to follow participants over several years to understand effects on behavior over time.
They’ve also created an interactive web tool to help other researchers explore their data. The tool allows users to see which interventions worked best for particular age groups, income levels, political ideologies, and other categories. Vlasceanu hopes it will be useful for her fellow scientists as well as for groups looking to increase climate engagement.
“Climate change is a collective problem and individual solutions alone are inadequate for addressing it,” Vlasceanu said. “This could help practitioners get a flavor of what kinds of messages resonate with their target audience to inspire collective action.”
Stanford co-authors include Robb Willer, professor of sociology in the School of Humanities and Sciences; Christoph Semken, a former postdoctoral scholar at the Stanford Environmental and Energy Policy Analysis Center who is now an assistant professor at the University of Toronto; Yash Patel, a PhD student in environmental social sciences in the Doerr School of Sustainability; and Ke Fang, a PhD student in psychology in the School of Humanities and Sciences.
This work was funded by the National Science Foundation, a Grantham Research Institute PhD Scholarship, a Cambridge Humanities Research Grant, the Keynes Fund, a CRASSH Research Grant, the Carlsberg Foundation, and an ERC Consolidator Grant.
Major socio-environmental processes in ecologically sensitive regions. Ecologically sensitive regionsare those which are highly vulnerable to the impacts of climate change and humanactivities, most significantly industrialization and urbanization, while theirecosystem services are low or reduced
The paper “Prioritizing Sustainable Development of Ecologically Sensitive Regions” was published recently inEcosystem Health and Sustainability – A Science Partner Journal. The innovative research calls for merging AI with indigenous knowledge and targeting “tipping point” ecosystems to achieve the Sustainable Development Goals.
A groundbreaking new study urges a global priority shift toward sustainable development in four types of ecologically sensitive regions, warning they are at imminent risk of catastrophic “tipping points” due to climate change and human pressure. The research, lauded by expert reviewers as “timely,” “innovative,” and “forward-looking,” proposes a novel integration of artificial intelligence (AI) with Indigenous knowledge and a unified scientific framework to prevent systemic collapse and guide equitable resilience.
Global Significance: Averting Cascading Crises
The study identifies four critical region types - plateau/alpine systems, resource-depleted regions, super-fast-growing cities, and island/coastal states - as disproportionately vulnerable. Despite their diverse geographies, they share a common trait: high sensitivity to shocks that can trigger irreversible damage with global consequences.
“These are not just local problems,” the study emphasizes. “The Tibetan Plateau’s melting glaciers threaten water security for billions across Asia. The collapse of a resource-depleted city can destabilize entire regions. Coastal overtopping can create climate refugees. Protecting these regions is a linchpin for global stability and achieving the UN Sustainable Development Goals (SDGs), particularly those related to water (SDG 6), cities (SDG 11), climate action (SDG 13), life under water (SDG 14), and life on land (SDG 15).”
Theoretical and Methodological Innovation: A Unified Lens and a Novel Fusion
The study’s core innovation is its unified social-ecological systems (SES) analytical framework, which allows policymakers to analyze disparate regions - from the Arctic permafrost to megacities like Shenzhen - through the same lens of exposure, sensitivity, and adaptive capacity. This approach reveals how ecological fragility and social vulnerability intertwine to create systemic risk.
Its most pioneering proposal is the integration of AI-enhanced monitoring (using satellite data and IoT sensors) with Indigenous and local knowledge. While AI can detect large-scale environmental changes, local communities hold deep, place-based understanding of ecological rhythms and resilience strategies. The study argues that fusing these knowledge systems is essential for accurate early warning and culturally appropriate solutions.
“AI can spot a forest canopy change from orbit, but local knowledge can explain why it’s happening and what it means for the community,” the paper notes. “This synergy is the future of sustainability science.”
Implications for Global SDG Implementation: A Blueprint for Ethical Action
To translate science into action, the study makes concrete recommendations with profound implications for global SDG implementation:
1. Establish a Global Sensitivity Observatory Network: A proposed international network would standardize monitoring of these critical zones using the integrated AI/local knowledge model, providing real-time data for global assessments and local action.
2. Governance for Equity and Justice: The research strongly warns against a purely technological fix. It calls for adaptive governance that empowers local communities, resolves policy conflicts, and ensures long-term political and financial commitment. Success hinges on placing equity and environmental justice at the center of all interventions.
3. An Ethical Framework for Technology: The study directly addresses ethical pitfalls, advocating for clear policies on data sovereignty, the use of understandable “explainable AI,” and participatory design. It insists that communities must own their data and have the right to contest AI-driven decisions affecting their lives and lands.
4. Targeted, Resilient Development: By providing a clear typology of sensitive regions, the framework allows the international community to prioritize funding, technology transfer, and policy support to where it is most urgently needed, making SDG implementation more strategic and effective.
The anonymous reviewers unanimously praised the study's ambition and relevance. They highlighted its “valuable synthesis” of interdisciplinary science and its “commendable” call for knowledge integration. It provides not just a warning, but an actionable roadmap. It argues that safeguarding the world's most fragile socio-ecological systems is the ultimate test of our commitment to a sustainable and just global future.
