Less than two weeks ago, Filipino climate negotiator Yeb Saño delivered a landmark speech on climate change. Speaking before delegates of 195 nations at the 19th conference of parties (COP) to the United Nations Framework Convention on Climate Change in Warsaw, Poland, Saño quietly wept as he recounted the devastation wrought by “this hellstorm called Super Typhoon Haiyan.” Uncertain of the fate of even his own family amid the “vast wasteland of mud and debris and dead bodies,” Saño’s words carried a palpable sense of loss, pain and angst.

As the strongest typhoon in history to make landfall, Saño argued the unprecedented storm must be considered an unnatural disaster. “It is not natural when the human species has already profoundly changed the climate,” he declared. “What my country is going through as a result of this extreme climate event is madness — the climate crisis is madness.”

Then, in a fateful turn, Saño departed from his prepared remarks: “In solidarity with my countrymen who are struggling to find food back home, I will now commence a voluntary fasting for the climate.” Continuing, he explained, “I will voluntarily refrain from eating food during this COP, until a meaningful outcome is in sight.” As a result, Saño became the first U.N. official to commit to such principled nonviolent action during a conference.

Saño’s speech galvanized thousands to fast for climate justice. In Warsaw, nearly a hundred negotiators and delegates fasted in solidarity with the people of the Philippines. The next day in Boston, students from Tufts and Brandeis universities put out a call on social media for a collegiate solidarity fast. Within several days, nearly 1,200 students around the world committed to a rolling fast and authored an open letter representing students from 75 universities. The World Council of Churches followed suit, urging its 500 million interfaith members to fast “in solidarity with the poor and vulnerable” and push for “global climate justice.” 350.org then organized over 50 worldwide vigils united under the message #WeStandWithYou. In another unprecedented move for a climate negotiator, Saño authored a petition — which garnered over 717,000 signatures — demanding immediate climate action in Warsaw.

Despite these gains, however, fasts and hunger strikes frequently fall flat, as was the case at COP 15 in Copenhagen four years ago. According to Adam Greenberg, a delegate for the youth-led American group SustainUS, that was because there were no concrete asks and no crucial government personnel who participated. This time, however, the situation was quite different. As UC Berkeley Professor Emeritus and Metta Center for Nonviolence founder Michael Nagler contends, Saño’s fast reflected sound Gandhian logic. According to Nagler, he is a man whose “heart is broken, who has tried everything else, and who seeks to emphasize his peoples’ suffering.” What is less clear, however, is the extent to which Saño’s fast — and wider solidarity actions — were an effective tactic for pressuring the negotiators at COP 19.

While Mohandas Gandhi considered fasting one of the greatest weapons in the arsenal of nonviolence, he urged it be used with caution and adhere to strict guidelines, especially when making demands of other parties. While Saño’s specific demand — “an international mechanism for loss and damage” to help developing nations cope with climate disasters — certainly qualifies as a concrete and realistic ask, Gandhi also advised that the fasters’ demands be directed towards empathetic members of the community. This stipulation was one reason why he never directed his own fasts towards the British — they didn’t see Indians as their equals and therefore weren’t likely to be empathic toward him. Similarly, Saño and the climate justice movement can’t expect empathy from the U.S. government, which not only carries great clout at these meetings, but also — according to chief U.S. climate negotiator Todd Stern — will not consider compensation or reparations as a form of climate action.

While fasting carries great challenges, it still can have great power, and climate justice advocates are using the tactic to their advantage. For one thing, Saño’s fast has served as a crucial bridge between communities of faith and climate justice advocates. As journalist Wen Stephenson has argued, the climate crisis is fundamentally a spiritual crisis that cannot be understood independent of morality. People of faith are increasingly calling for “sustainability, justice, inter-generational equity,” and other acts of “creation care.” In that sense, fasting can connect individuals’ personal sacrifice and spirituality with broader social imperatives, and — in time — it might even provoke people of faith to take more direct nonviolent actions.

Furthermore, this fast has deepened a burgeoning global youth climate justice movement. Calls for solidarity fasts among U.S. college students emerged from newly-organized fossil fuel divestment campaigns. Youth activists were quick to understand that unnatural disasters like Super Typhoon Haiyan are the natural consequence of unchecked fossil fuel extraction. Those who are fasting reside in nations as diverse as Fiji, Egypt, Singapore, Croatia, South Africa, China, Australia, Cyprus and, remarkably, the Philippines. These students are affiliated with a diverse array of organizations, from the Arab Youth Climate Movement to the Federation of Young European Greens. Increasingly connected by the Internet and a common recognition that humanity must keep 80 percent of known fossil-fuel reserves in the ground, these students are among those who stand to lose the most from inaction and are rapidly emerging as the vanguard of climate justice activism.

Finally, the fast is serving as an important tactic for provoking public awareness. As Adam Greenberg noted, “Suddenly my friends who didn’t care about COP — who really rolled their eyes at me and didn’t think it was an effective use of anyone’s time — are now all paying attention.”

Yet, despite these promising benefits, fasts are generally insufficient on their own. As Nagler explained, “Historically social justice and peace movements have not had a way of capturing momentum from one-off spontaneous protests like fasts.” Without translating the gains of fasting into other forms of activism, participants often revert back to a state of disengagement and their fast remains mere opinion. Nagler instead calls for the “ratcheting” of tactics to preserve the emotional energy of fasting and ensure that movements do not stall.

One way activists can do this is by pushing for domestic pressure to leverage international climate progress. Since Saño’s speech and the solidarity fasts “suddenly made COP a story,” as Greenberg noted, the climate justice movement should integrate the annual conference into its overall strategy. Greenberg also believes that activists need to build public support and galvanize political will with the U.N. process in mind — an understanding that has thus far eluded most advocates.

Since the domestic politics of intransigent developed nations — especially the United States, Canada, Japan and Australia — are crucial for a binding global treaty on carbon emissions, U.N. climate meetings are occasions for prolonged and escalated activism. Greenberg says this is especially true for COP 21 in 2015, when the Kyoto Protocol — the only internationally-binding agreement to reduce greenhouse gas emissions — is set to be replaced. Activists can help determine, “whether that binds us into something good, or something straight out of a horror film.”

For all the talk about building on the momentum of Saño’s fast, there is something fundamentally basic about its execution: In the face of government inaction, resistance — for Saño — felt essential. This is because in its own small, but truly revolutionary way, fasting can help overcome fear and fatalism.

Thanks in part to Saño’s principled 13-day fast, the delegates of COP 19 reached a last-minute deal on Saturday to establish a modest “loss and damage” mechanism. Most importantly, the delegates established this new plank independently of the conference’s existing mitigation and adaptation groups — enabling it to make a significant contribution in the coming years. Yet green groups contend this modest provision is insufficient, deriding the conference as “the dirtiest on record.”

In another sign of their displeasure, over 800 members of civil society — in an unprecedented move — walked out of the COP 19 proceedings on Thursday. Fed up with the complicity of corporate politicians, they declared, “Polluters talk, we walk,” vowing to return stronger and more determined than ever next year. Friends of the Earth proclaimed the walkout a success unto itself, since it “started a domino effect already reaching our home countries, where ordinary citizens are joining the struggle for climate justice.”

If such individual and collective refusals can be seen as the seeds of a more sustained and radical activism, the quiet fasting of COP 19 may well become the tumultuous direct action of COPs 20 and 21.