TL;DR: EA has traditionally deprioritized climate change as a cause area. But a new report from Rethink Priorities, an EA research institute, suggests that specific Earth systems risks driven by climate change could have mortality impacts comparable to major global health burdens, on top of the known damages of climate change. 

The report finds that research and governance work on ‘Earth Systems Stabilization’ to establish whether safe options to address these risks exist clears EA cost-effectiveness bars and justifies significant funding.

Disclosure: I run the Climate Change program at The Navigation Fund, a philanthropic foundation that also works on Farm Animal Welfare and Transforming Criminal Justice. Building on these research findings, we will be jointly launching an Earth Systems Stabilization Fund with Outlier Projects, who commissioned the research. The report interviews me and leaders of organizations we already support and recommends funding work in areas where they operate.

When we launched The Navigation Fund’s Climate Change program last year, we looked for an area within climate change where our dollars could be especially effective. One area we’ve chosen to focus on is “Earth Systems Stabilization” - a new umbrella term to describe the work of understanding, predicting, and trying to prevent the deterioration of critical Earth systems impacted by climate change. Here we mean things like:

• Increasing ecosystem emissions: Rising temperatures are increasing emissions from ecosystems. Tropical wetland outgassing, thawing permafrost, and forest fires account for a growing share of total emissions. These feedback loops could amplify global warming by 30%.
• Weakening ocean currents: A massive system of ocean currents called the Atlantic Meridional Overturning Circulation (AMOC) could significantly weaken this century. This would severely disrupt Asian and West African monsoons and shift the global tropical rainbelt southward, causing major droughts in some regions and catastrophic flooding in others.
• Declining planetary reflectivity: Declining cloud cover and sea ice are making the Earth less reflective, causing it to absorb much more solar energy.
• Rising sea levels: Sea levels are now predicted to rise 2–7 feet by 2100 which would displace hundreds of millions of people. More than 90% of risk and uncertainty is due to instability in the Thwaites Glacier in West Antarctica.
• Response options: Approaches to managing these risks include climate interventions like stratospheric aerosol injection, marine cloud brightening, and ice-sheet stabilization (all covered in the report), as well as other approaches like wetland management, sea-ice thickening, methane mitigation, and wildfire prevention (not in the report). 

These risks do not depend on pessimistic assumptions about future emissions trajectories; some risks, like rising sea levels due to Thwaites Glacier, have tipping-point dynamics where today’s warming may already be enough to lock in substantial future loss. This makes it a distinct but complementary field to decarbonization, because it targets risks that emissions cuts alone will not address. A forum post from May 2026, "Climate Stabilization: A draft ITN update", makes the conceptual case for EA funding in much greater detail. 

We think that Earth Systems Stabilization deserves more attention and resources, but traditional climate philanthropy has neglected to invest in understanding and addressing these specific risks despite their massive impact (by our estimate, funding is in the low tens of millions annually). To assess whether this work would make sense as an EA funding priority, Outlier Projects commissioned Rethink Priorities to investigate this work and evaluate it against EA benchmarks for impact. 

The report comes to a clear conclusion: Earth systems instabilities could cause millions of deaths, and an EA fund in the hundreds of millions of dollars to address these risks is well-justified. We agree with these conclusions. However,  we (and Rethink Priorities) would like to continue to stress-test the assumptions behind this argument, and invite questions, comments, and suggestions for further research. 

Below, I’ve included Rethink Priorities’ full executive summary from their Substack post launching the report. Rethink Priorities also did a presentation on their report at EAG NYC 2026 which directly compared mortality from Earth systems instabilities to global health issues like malaria, which I’ll add to this post when available. 

Click here to see the full report. 

Earth Systems Risks and the Case for Funding Stabilization Research

Why new evidence suggests the effective altruism community should reconsider its approach to climate research

In research commissioned by Outlier Projects, Rethink Priorities’ Global Health and Development team reviewed recent climate science and interviewed roughly 20 experts. We asked whether there is a case for the EA community to fund research on Earth systems stabilization. We concluded that there is.

The effective altruism community has historically deprioritized climate change as a cause area for two main reasons. The first is a judgment that climate change is unlikely to pose a direct existential risk to humanity (Ord, 2020; Hilton, 2022). The second is that it is not neglected: global climate funding from public and private sources reached approximately $1.3 trillion annually between 2021 and 2022 (Buchner et al., 2023; UNFCCC, 2024).

However, Earth system destabilization could be considered distinct from the broader climate change area, because it involves the triggering of mechanisms that can effectively decouple from the rise (and ideally later fall) of global average temperatures.

Evidence published since IPCC AR6 suggests that several Earth systems (ice sheets, the AMOC, planetary albedo, frozen carbon stores) are destabilizing faster than models predicted. Many of these have potentially irreversible, self-reinforcing dynamics that would be unresponsive to future reductions in global average temperatures, once triggered.

The human harms of destabilization are large even on deliberately conservative estimates. Counting only direct mortality (no morbidity, economic damage, or interactions between risks), our BOTECs find: ~15 million excess deaths by 2100 per additional degree of warming; $17.8 trillion in philanthropic value at stake from 1.5m of sea level rise (230 million people live below 1m above the high-tide line today); and $10.5 trillion in probability-weighted damages from a 15% chance of AMOC collapse.

This justifies a fund in the low- to mid-hundreds of millions. At Coefficient Giving’s (CG) old 2000x bar, each of the four risks individually supports an EA community willingness to pay of $263–445 million (single funder: $131–223 million) for research and governance work. These numbers would need to be off by 3–4 orders of magnitude for the case to entirely collapse. Moreover, CG’s bar has fallen to 1000x since publication, effectively doubling our WTP estimates for averting deaths in this cause area.

We explore the mechanisms and funding landscape of three candidate climate stabilization approaches: stratospheric aerosol injection, marine cloud brightening/thinning, and ice-sheet stabilization. All are contested, and none are deployment-ready. We recommend funding the research and governance work needed to establish whether safe, workable options exist.

The post continues here.