Yassamin Ansari’s tentative plan after graduating from college was to work with refugees in Turkey. But a brief phone call with Bob Orr, then-Secretary-General Ban Ki-moon’s climate adviser at the United Nations, changed her mind. He explained how global warming exacerbates existing problems, including refugee crises. “I was 100% convinced that I needed to go work for him at the UN and on climate,” she says. So she did.

After helping work on the Paris Agreement at the UN and organizing some climate conferences, she moved back to her home state of Arizona. There, the Iranian-American tackled climate issues as a member of the Phoenix City Council, helping establish the city’s heat office and pushing through a plan to electrify city buses by 2040.

Now in federal office, she’s calling out the fossil fuel industry’s influence in Washington and introducing legislation on extreme heat “so that Arizonans can afford to keep their air conditioning on in the summer,” she says.

In the past few years, the bike bus has emerged: hundreds of elated kids on bikes zooming down suburban streets and bopping to pop tunes. Sam Balto didn’t invent the bike bus—but he can claim some credit for making it go global. The Portland, Oregon-based physical education teacher and dad of two started cycling to school with a flotilla of students back in 2022, inspired by a video of adults and kids pedaling around together in Barcelona. “I just wanted to give kids a joyful, active start to their day,” Balto says. “But it turns out that this taps into something deeply human.”

Since then, Balto’s euphoric social media videos have inspired people around the world. Now he has a profile he never predicted: In January singer Justin Timberlake, whose music has soundtracked many morning rides, hopped on Balto’s bike bus in person.

Balto co-founded a nonprofit, Bike Bus World, in 2024 and has helped hundreds of new bike buses to launch. He travels to spread the bike bus word, and he’s now pushing more city leaders and schools to formally support biking en masse to school. The bike bus “solves so many problems in such a joyful, visible and low-tech way,” he says. “It’s culture change at kid speed.”

Pepukaye Bardouille had just moved to South Africa in September 2017 to work on improving energy access in impoverished communities when she got news that her home country, Dominica, had been hit by Category 5 Hurricane Maria.

The storm killed 65 people and damaged 90% of homes, including Bardouille’s family property. The single mother moved her two small children back to the devastated island to lead the recovery and rebuilding effort.

Her work caught the attention of Barbados Prime Minister Mia Mottley. In 2022, Mottley launched the Bridgetown Initiative. It aims to reform the global financial system to enable vulnerable nations to tackle the effects of climate change and crushing debt. Bardouille later became its director and special adviser on climate resilience to Mottley. Under her, the initiative has prioritized engagement with insurance companies, with the goal of unlocking investment and lowering premium costs.

Separately, Bardouille wrote Barbados’ $12 billion national investment plan, which relies on private-sector capital mobilization as well as refinancing debt at a lower interest rate. She’s reinvesting the saved money back into sustainability solutions such as nature preserves and getting more insurance. She hopes it will be a template for other small countries.

The costs of building thriving and sustainable economies are enormous, Bardouille says, and in this political environment, a large amount of the money “must come from the domestic capital markets.”

Ex-Tesla Inc. executive Nick Carter’s battery storage developer is transforming Australia’s grid. Akaysha Energy, which is owned by BlackRock Inc., is working on 11 projects in a market in which grid-scale batteries are rapidly facilitating the closure of coal-fired power plants.

Its Waratah Super Battery, north of Sydney, is one of the largest projects of its type outside China and is intended to act as a “shock absorber,” helping to maintain reliable electricity supply during bushfires or lightning strikes. It will also help boost power capacity on transmission lines serving major cities.

The partially ready site was called into action in November, sending power to the grid as a severe heat wave gripped New South Wales, Australia’s most populous region. “That was enough to actually keep the state from going black,” Carter says.

Next up: The company plans to expand abroad to Texas, Virginia and Japan.

Making beer is a relatively emissions-heavy process, but Andrew Collins has engineered a novel way to cut New Belgium Brewing’s carbon pollution. The Colorado-based brewer has a new system that captures carbon dioxide produced during the fermentation stage, then cleans, compresses, filters, dries and liquifies it before pumping it back into the final product to carbonize the beer. It’s entirely safe to drink and, once ingested, no longer a greenhouse gas.

It’s one of the many climate hacks Collins has crafted since starting as New Belgium’s carbon neutral engineer four years ago. He oversees an array of small solar farms, generators that run on biogas waste and turbines that spin up power from wastewater treatment at the company’s six breweries. Recently he brought in a first-of-its-kind electric boiler, making New Belgium the first customer for the product.

“The type of projects that are making the most impact at the moment, they’re brick and mortar,” Collins says. “We are pouring concrete. We’re buying equipment.”

Despite his work, the company’s emissions increased by about one-third from 2019 through 2024, though its production in that time surged as well. Collins has managed to cut New Belgium’s emissions per beer by almost 10%, but there’s more to do: The company aims to reduce direct emissions by at least 55% and run entirely off renewable electricity before 2030.

Gretchen Goldman helped shape former President Joe Biden’s climate justice agenda as one of his science advisers. Now she’s working to stop the Trump administration’s rollbacks and lay the groundwork for restoring what gets dismantled.

“All of that is under threat with the smashing of federal agencies and firing of government scientists and destruction of American science in ways that we have never seen before,” Goldman says. “We’re very focused on, ‘What does it mean to hold the line, save as much as we can,’ and also, ‘What needs to happen in the long term?’”

The Union of Concerned Scientists has mobilized its network to defend US science and scientists in the courts—for example, joining a lawsuit against Elon Musk and his Department of Government Efficiency for exceeding their powers. Experts from the group’s 20,000 members periodically testify in Congress, including recently on the reconciliation bill.

“I think there were reasons to be fearful given what we’ve seen in these first hundred days,” she says. “But at the same time, I’m reminded of the bravery and stubbornness of the scientific community.”

The scientific process can be painstakingly slow. Jon Hennek is working to speed it up at Lila Sciences. Lila’s goal is to perform cutting-edge research in sustainability and life sciences, with Hennek driving the use of artificial intelligence to develop catalysts and materials key to the energy transition.

Over the last two-and-a-half years, the company has investigated millions of materials using AI and tested the most promising ones in the lab. That includes testing the efficacy of novel sorbents used to capture carbon from air, a technology needed to avert the worst impacts of climate change.

While it’s hard to say exactly how much time AI saves, Hennek says the pace of the work feels dramatically different from an all-human lab, where the process of gathering relevant research, creating a hypothesis, setting up an experiment and running it for a single material can take months or even years.

“What Lila is trying to do is fundamentally accelerate the entire wheel of science, not just finding how to do parts of it better,” he says. The company emerged from stealth mode earlier this year with $200 million in funding.

Before Lila, Hennek worked at Osmo, a company spun out of Google attempting to teach AI to develop a sense of smell, which could have medical applications. Prior to that, he worked on software that helped farmers implement carbon-sequestering practices. Getting back to his roots by focusing on emission cuts, Hennek says, is what drew him to Lila.

When Sarah Kapnick was at Princeton University in the early 2000s, her professors advised that the two surest bets for math majors were either a job in finance or a career in climate science. In the 20 years since then, Kapnick has combined the two. “They’ve always been linked in my head,” she says.

Having been appointed by the Biden administration as chief scientist for the US National Oceanic and Atmospheric Administration in 2022, today Kapnick is JPMorgan Chase & Co.’s global head of climate advisory. Along the way, she’s developed a talent for translating concepts such as atmospheric CO₂ levels and permafrost thaw into the language of profit and loss.

She’s become a rare voice on Wall Street willing to speak up about climate change. At JPMorgan, she explains to CEOs the very real risks a warming world poses to their businesses. Since February, Kapnick has published a series of papers advocating for climate-aware decision-making, writing about insurance and climate adaptation.

“Science put on a shelf has no value: You actually have to use it,” she says. “I’m trying to show that that can be done at the biggest bank in the world.”

—Alastair Marsh

During the pandemic, Kakani Katija spotted Pokémon Go players wandering outside her home using their phones to search for imaginary creatures. That inspired Katija, leader of the Monterey Bay Aquarium Research Institute’s Bioinspiration Lab, to create a gaming app called FathomVerse. Its players are training AI-enabled robots to track and identify ocean organisms crucial to the carbon cycle.

“I thought, ‘Surely we should be able to generate similar excitement using real ocean animals,’” Katija says.

Scientists have collected millions of images of marine organisms, but upwards of 60% of species remain unidentified. The FathomVerse app for phones and tablets populates a virtual ocean with real images of unknown critters, which players try to classify. In the year since FathomVerse’s debut, more than 30,000 players from 177 countries have reached consensus on the identity of more than 139,000 previously unlabeled images, helping train the lab’s AI.

This summer, Katija’s team plans to test an autonomous underwater robot equipped with an AI refined by FathomVerse data. The robot will, of its own volition, search for specific species and collect data. The goal is to deploy a fleet of underwater AI-enabled drones constantly monitoring marine animals to gain insight into the ocean’s impact on global climate.

“We know that ocean animals play an important role in carbon cycling, but we don’t know to what extent,” Katija says. “FathomVerse is helping us fill in those gaps.”

The Duwamish River is the story of Seattle: It’s the home of tribal communities, the dumping ground for industry, the inland connection to the city’s seaport and, more recently, an indictment of the region’s inequality.

Its legacy shapes Paulina Lopez’s work leading the Duwamish River Community Coalition, an environmental justice, advocacy and cleanup organization fighting for the river and the people who live in its valley. When she started volunteering with the group, she says, life expectancy in the riverside town of South Park was 13 years lower than in wealthy neighborhoods north of Seattle. Children have higher rates of asthma hospitalization in the town as well.

Parts of the river are designated as a Superfund site, and Lopez’s group is making sure governments, the Port of Seattle and Boeing Co. clean up the toxin-infused sediment.

“We’re trying to clean the neighborhood, but what I wanted to concentrate on is the community aspect of it,” Lopez says. “It’s crucial to bring community voices to the center of everything—especially those who have been impacted the longest by injustices.”

As devastating fires ripped through Los Angeles in January, downloads of Watch Duty skyrocketed. Millions of people relied on the app to track the spread of fire and evacuation orders.

Watch Duty isn’t made by the federal government or a high-flying startup; it’s run by John Mills, who launched it in 2021 after a wave of fires, including one that came perilously close to his rural Northern California ranch. “There’s no siren, there’s no alert, there’s no nothing,” Mills says. “I was like, what is going on here?”

He and David Merritt, chief technology officer, co-founded Watch Duty to help centralize information about Western fires. It relies on 200 volunteers and 20 paid staff members to tap into a massive amount of intel—from emergency radio traffic to satellite imagery and monitoring cameras—and push out real-time updates.

The app shoots to the top of app store downloads during severe fire outbreaks. And while Watch Duty offers paid memberships with extra features, Mills says basic safety information will always be free.

He aspires to track all types of natural hazards nationwide to become “the disaster app.” The service’s utility will only grow as the planet warms. “The data is showing us that things are changing,” Mills says. “We’re in danger.”

An “optical illusion.” That’s how Chandni Raina characterized the $300 billion climate finance deal clinched at COP29. The last-minute criticism was her breakout moment.

Raina has repeatedly called on richer nations to spend more to help the Global South cut emissions and cope with the effects of warming. Based in New Delhi, the finance ministry official has argued for low- and middle-income countries to have a greater voice at international negotiations.

“Access to finance at affordable costs for developing countries is vital for climate action by them,” she says.

She has worked as a civil servant for nearly three decades, dealing with industrial disputes, child labor and intellectual-property rights. She began handling the climate finance portfolio in 2020 and has been part of UN negotiations since 2021.

This year, Raina has been shaping India’s much-awaited framework and rules for climate finance, with the aim of securing foreign direct investments for nascent technologies such as green hydrogen as well as climate adaptation. —Ishika Mookerjee and Shruti Srivastava