Joshua discusses the Advance Research for Climate Emergencies (ARC) Initiative at Renaissance Philanthropy, through which the team identifies experts and ideas, incubates them from small seed grants into fully staffed build-grant programs, and launches them.

Joshua traces his ambitious, technically rigorous approach to his years at DARPA, which gave him permission to chase ideas others called impossible. Widely sought out for mentorship, he talks about the Climate Emergency Forum and issues an appeal to scientists and nonprofit leaders.

*Tacit Knowledge *
Hosted by Kumar Garg
Presented by Renaissance Philanthropy
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FOLLOW JOSHUA

LinkedIn: https://www.linkedin.com/in/joshuawrightelliott/

Substack (The ARC): https://arcinit.substack.com/

KEY QUESTIONS & TAKEAWAYS

What is the "Sulfur Tracking Program" trying to figure out?

An in-development ARC initiative (still under a stealth name) aimed at launching small satellites and balloon-based sensors to resolve one of climate science's biggest open questions: how much of the Earth's declining reflectivity is due to falling aerosol pollution versus a warming-driven feedback loop that's itself reducing cloud cover.

Why might Earth's declining reflectivity be as big a driver of warming as greenhouse gases?

NASA's CERES satellite data suggests the planet has lost enough reflectivity since 2000 to contribute roughly 2.7 W/m² of climate forcing — a number comparable to the instantaneous forcing from all greenhouse gases emitted since the Industrial Revolution. That comparison is still being finalized in peer review, but it points to a second, under-discussed pillar of climate change alongside emissions.

Why has industrial pollution been masking warming, and what happens as it's cleaned up?

Burning fossil fuels releases sulfur dioxide and other aerosols that seed brighter, more reflective clouds. That pollution layer is estimated to be offsetting about half a degree of global warming — meaning, as Joshua puts it, we're already living in a "near two-degree world" that's been masked by the dirtiest possible form of accidental geoengineering. As pollution controls reduce aerosol emissions, that masking effect declines too.

What's driving the rest of the loss in Arctic ice and cloud cover?

About 30% of lost reflectivity comes from vanishing ice and snow cover (largely Arctic sea ice, mountain glaciers). The remaining majority comes from changes in cloud cover — and current observational and modeling capabilities can't yet disentangle how much of that is falling aerosol pollution versus a self-reinforcing, warming-induced feedback loop.

Why do the most accurate climate models predict more warming, not less?

A recent study comparing the ~40 global climate models in the CMIP archive found that the models which most accurately reproduce observed changes in reflectivity and Earth's energy imbalance also tend to show 1.5–2x higher climate sensitivity than the model average. If those more accurate models are right, a projected 2.5–3°C future could actually be closer to 4.5–5°C.

What is the Heilmeier Catechism, and how does Joshua use it?

A set of pressure-testing questions developed by former DARPA director George Heilmeier to evaluate research proposals. Joshua distills it into four core questions he uses as a first-pass filter for any ambitious idea: what are you trying to do, who's doing it now and what's wrong with that, what's your big insight, and who cares.

What are the ARC Initiative and BiTS?

ARC (Advanced Research for Climate Emergencies) is Renaissance Philanthropy's "nonprofit venture studio" model for finding experts and ideas and building them into fundable climate programs, incubating efforts like the Arctic Stabilization Initiative. BiTS (Big if True Science Accelerator) is a related program Joshua co-designed to teach scientists and engineers how to turn ambitious ideas into coordinated, fundable research programs — modeled on the DARPA program-manager playbook.

On program design and ambition

• Joshua credits his time at DARPA with giving him "permission" to think in 20–40 year horizons and pursue ideas most people call impossible — his rule of thumb is that if fewer than 30% of the people you talk to say your idea is impossible, you're not being ambitious enough.
• His approach to building expertise quickly is deliberately social: talking to 20 to 100 people in a dense stretch of time, using each conversation to get referred to others, rather than relying only on published research.
• His most recent program-design insight is about timing: bringing in a wide group of field experts (a "PI meeting" or workshop) only once there's a strong-enough shared mental model to make the conversation productive — citing the "forming, storming, norming, performing" framework for how new groups become effective, and the goal of minimizing time spent "storming."

Links:

• Joshua Elliott — Chief Scientist at Renaissance Philanthropy. Previously a Program Manager at DARPA's Information Innovation Office for six years, where he directed nearly $600M in federal R&D funding; before that, spent almost a decade in academia on computational climate economics and energy systems modeling at the University of Chicago and Argonne National Laboratory.
• Renaissance Philanthropy — The organization producing Tacit Knowledge Podcast, where Joshua leads climate and energy program development.
• ARC Initiative (Advanced Research for Climate Emergencies) — Renaissance Philanthropy's philanthropic fund and "nonprofit venture studio" for translational R&D on catastrophic climate risks — tipping points like ice sheet collapse, Arctic destabilization, and runaway methane emissions — which incubated the Arctic Stabilization Initiative.
• BiTS (Big if True Science Accelerator) — A 15-week accelerator co-designed and co-run by Joshua Elliott and JP Chretien (both former DARPA program managers) that teaches scientists and engineers how to turn ambitious ideas into fundable, coordinated research programs.
• NASA CERES (Clouds and the Earth's Radiant Energy System) — The NASA satellite mission, operating continuously since March 2000, that measures Earth's energy imbalance — the data source behind Joshua's reflectivity-loss figures.
• Heilmeier Catechism — A set of questions developed by former DARPA director George H. Heilmeier to pressure-test research proposals; DARPA's official version lists eight questions, though Joshua describes using a compressed four-question version of his own in practice.

Describing herself as a "tri-sector athlete" who has moved between government, academia, and the private sector, Cara talks about growing Pitch Fest, which pairs city government agencies with academics and civic technologists willing to help solve specific, openly shared problems, from 100 attendees and a few agencies in its first year to 40 participating agencies and 104 pitches, with 100 of those pitches drawing at least one interested expert.

Cara talks about collaborations, cold-emailing, and the power of connection.

*Tacit Knowledge *
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LinkedIn

https://www.linkedin.com/in/cara-eckholm-506b2236/

KEY QUESTIONS AND TAKEAWAYS

What is Pilot City

A matchmaking program, started by Cara Eckholm in New York, where city agencies pitch specific problems they need help with and local researchers or technologists apply to work with them — flipping the usual model where academics pitch ideas in search of a government partner.

How does the matchmaking process actually work?

City agencies present problem statements in short, informal pitches (originally modeled on how Stanford classes help students find startup co-founders). Interested researchers and technologists then apply to work with a specific agency, and the agency chooses who they want to work with from the applicant pool.

Why build a "buyer-first" model instead of starting with researchers' ideas?

Eckholm observed that both sides were siloed: academics and civic technologists had ideas for improving cities but no government partner, while city agencies had unmet needs but no channel to reach outside talent. Starting with the agency's stated problem — the "buyer" — rather than a researcher's proposal solved the matching problem directly.

What makes a city a good candidate for a Pitchfest program?

A metro population of at least a million, a government champion willing to publicly share unsolved problems (which runs against how most agencies communicate), and either a research university or an active civic tech community — most U.S. cities already have the latter.

What's a real-world example of this kind of collaboration paying off?

Economist Al Roth was approached by an NYC Department of Education official who had read his work on medical residency matching and asked him to help redesign the city's high school placement process. The redesign was later adopted in Boston, and Roth went on to win a Nobel Prize for that work and related market-design research, including kidney-exchange matching.

How much traction has the program gotten?

In its most recent year, 40 agencies submitted 104 pitches, and 100 of those pitches drew at least one interested researcher — some drew as many as 20. The program is now expanding beyond New York to Boston, Hennepin County (Minneapolis), Los Angeles (water district), and Philadelphia (regional transit).

What's holding academia back from more of this kind of applied work?

Tenure and promotion structures reward publication in a narrow set of journals, not applied public-sector collaboration — to the point that one professor Eckholm spoke with left his work as a city and White House housing policy adviser off his tenure application, worried it would make him look like an activist rather than a scholar.

On career and confidence

• Eckholm's own path into this work began with a cold email — she reached out to her boss's boss, former NYC Deputy Mayor Dan Doctoroff, offering to help with a post-pandemic economic recovery commission, with no idea if he'd respond. That opportunity ended up shaping the next several years of her career.
• Her tacit-knowledge takeaway is what she calls "delusional confidence" — treating open calls for applications ("apply even if you're underqualified") literally, and being willing to send many speculative emails knowing only a fraction will land.
• She distinguishes this from overconfidence: the goal isn't to claim expertise you don't have, but to clearly articulate what value you could add and let curiosity — not credentials — carry the pitch.

Links:

• Cara Eckholm — Founder of Pilot City; also founder of AKA Urban, an advisory firm for public-sector building projects.
• Pilot City — A program of Renaissance Philanthropy aimed at strengthening state capacity by helping cities, counties, and regions tap into the scientific and technical expertise already present in their communities. Its flagship format is the Pitchfest — a bottom-up matchmaking event where government agency staff pitch problem statements and get paired with regional experts. Pilot City began in New York in 2023 and, with support from the Sloan Foundation and later Coefficient Giving, has since expanded the Pitchfest model to Boston, Hennepin County, and other regions.
• Renaissance Philanthropy — The organization producing Tacit Knowledge Podcast; Cara is a fellow there.
• Cornell Tech's Urban Tech Hub — Where Eckholm did her original fellowship and where Pilot Pitchfest first launched.
• New York City Economic Development Corporation (NYCEDC) — The city agency partner from Eckholm's original fellowship research on agency innovation capabilities.
• Alfred P. Sloan Foundation — Seed funder of the first Pitchfest event.
• Al Roth — Economist (Harvard, then Stanford), 2012 Nobel laureate in Economic Sciences for work on market design — the "knock it out of the park" example Cara cites, where a cold outreach from an NYC public servant led to Roth redesigning the city's high school matching process.
• Mechanism design — The field of economics concerned with designing rules and institutions — like matching markets — to produce a desired outcome; the broader discipline Roth's work belongs to.
• Medical residency match (NRMP) — The National Resident Matching Program, also known as "The Match" — uses the applicant-proposing algorithm that Roth's research built on and that also underlies the NYC high school match and kidney-exchange matching.
• Dan Doctoroff — Former NYC Deputy Mayor for Economic Development (2002–2008), later CEO of Bloomberg L.P. and Sidewalk Labs — the boss's-boss Cara cold-emailed, which opened her path into city work.
• Sidewalk Labs — Alphabet's urban-tech incubator, where Doctoroff later served as CEO and which Cara also applied to.

Charlotte discusses what drove her to assemble ASI's team and create a roadmap around that end goal from the start, and the advice and mindset that led her to make a deliberate departure from how she'd seen other organizations in the field start out.

Charlotte talks about the role her delivery focus has played in her own career shift, growing impatient with research that wasn't translating into action fast enough, and what pushed her to build something explicitly designed to produce usable, actionable outputs.

Charlotte’s fascinating story sheds light on how to find problems worth working on.

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LinkedIn: linkedin.com/in/charlottebeall

KEY QUESTIONS AND TAKEAWAYS

What is the Arctic Stabilization Initiative?

Housed at Renaissance Philanthropy and directed by Charlotte DeWald, ASI is stage-gated research designed to give governments and multilateral organizations the safety, efficacy, and feasibility data they'd need to evaluate Arctic-targeted climate interventions — not to deploy interventions itself.

Why isn't decarbonization enough to stop Arctic tipping points?

Climate action has three points of attack rather than two. Decarbonization and adaptation get the most attention, but neither addresses near-term "tipping point" risk already locked in by processes like sea ice loss and permafrost thaw. ASI focuses on the third arm: regional climate stabilization in the Arctic.

What are Arctic tipping points?

Once certain climate thresholds are crossed, DeWald explains, the resulting state change is irreversible on human timescales — and the Arctic is where several of the most imminent thresholds converge, making it a first test case for humanity's tipping-point response.

What types of Arctic climate intervention exist?

There are three broad categories: increasing atmospheric reflectivity, structurally reinforcing ice sheets and sea ice, and increasing atmospheric emissivity — helping trapped heat escape. DeWald's research focuses on the third and least-understood category.

Why do mixed-phase clouds warm the Arctic instead of cooling it?

Mixed-phase clouds cover roughly 60% of the Arctic and trend net-warming, not cooling. Because they sit low to the surface and much of the Arctic year has little sunlight to reflect, these clouds act more like a "hat" trapping heat than a shield blocking it.

What is mixed-phase cloud thinning?

The proposed intervention is to nudge clouds into ice formation to help them dissipate. The mechanism relies on ice-nucleating particles — rare naturally occurring particles that trigger ice formation at temperatures far above freezing — a topic DeWald spent roughly a decade researching via shipboard instrumentation and national-lab modeling collaborations.

Is Arctic cloud seeding a new or untested technology?

The approach is neglected, not infeasible. Cloud seeding and cloud shaping are established techniques; what's missing is the applied research connecting them specifically to Arctic stabilization. DeWald built the initiative largely by cold-calling experts across disciplines to pressure-test whether a five-year research agenda was viable.

Beyond the science

1. DeWald's path to ASI came from friction with the pace of climate science. After a decade studying aerosol-cloud interactions — widely regarded as one of climate science's most persistent uncertainties — she concluded that incremental scientific understanding wasn't translating into commensurate action, which pushed her toward field-building instead of continued lab research.
2. Defining the "end user" early shaped ASI's structure. A conversation with a former U.S. diplomat (ex-UN envoy for East Africa, USAID) helped DeWald realize the initiative needed a diplomacy function from the outset — since the research is only useful if there's a clear pathway to the governments and multilateral bodies who'd act on it.
3. DeWald's tacit-knowledge takeaway: talk to people, not just papers. Her throughline across the episode is that expertise compounds through networked conversation — knowing who to call, and being willing to call them — as much as through individual technical depth.

Open asks from the episode: DeWald is looking to connect with people in conservation (for perspective on intervention risk/tradeoffs), scientists developing Arctic sampling platforms or sensors, and anyone who can "think programmatically" about field-building. She's reachable via Substack and LinkedIn.

Links:

• Charlotte DeWald — Program Director of the Arctic Stabilization Initiative at Renaissance Philanthropy. An atmospheric scientist specializing in ice-nucleating particles — the rare aerosols that trigger cloud ice formation — she holds a Ph.D. in Climate Science from Scripps Institution of Oceanography.
• Arctic Stabilization Initiative (ASI) — A five-year, stage-gated research program producing the evidence governments and multilateral organizations would need to assess whether Arctic-targeted climate interventions are safe, effective, and feasible. Its first focus is Mixed-Phase Cloud Thinning.
• Renaissance Philanthropy — The organization producing this podcast and housing the Arctic Stabilization Initiative.
• Mixed-Phase Cloud Thinning (MCT) — The intervention ASI is evaluating first: seeding Arctic mixed-phase clouds — which cover roughly 60% of the Arctic and trend net-warming — to trigger ice formation and help them thin or dissipate, allowing trapped heat to escape.
• Ice-nucleating particles — Rare naturally occurring particles that trigger ice formation in clouds at unusually warm temperatures — the subject of Charlotte's decade of prior research and the scientific foundation underpinning MCT.
• Aerosol-cloud interactions — The broader, still highly uncertain field of climate science Charlotte spent a decade working in before founding ASI — studying how aerosols shape cloud behavior and, in turn, the Earth's radiative balance.
• Decarbonization and CDR (carbon dioxide removal) — The two dominant strategies in climate action that Charlotte argues are necessary but insufficient on their own to prevent near-term Arctic tipping points, given warming processes already underway.
• Joshua Elliott — Chief Scientist at Renaissance Philanthropy — the person Charlotte ultimately connected with through networked phone calls, whose own climate and RenPhil background helped bring ASI into being.
• Never Split the Difference by Chris Voss — The negotiation book Charlotte references as something she's currently studying. Note: the transcript mishears the author's name as "Chris Fosse" — corrected here to Chris Voss.