Jeremy Grantham on Investing in Green Tech | Conversations with Tyler

29 Jan 2026 · 48 min
48:28

In this hour‑long interview, host Tyler Cowen talks with veteran investor Jeremy Grantham about the material constraints and systemic risks facing the global green transition. Grantham argues that known lithium reserves would cover only about 5% of the material needed for a fully electrified economy, urging a shift toward sodium‑ and potassium‑based batteries and noting his foundation’s investments in technologies that can extract three to four times more lithium from brine and 50% more from rock. He explains that wind and solar have near‑zero marginal cost, but the massive upfront construction energy demand temporarily raises fossil‑fuel consumption, creating a paradox where greening initially boosts fossil use. Grantham expands the discussion to other under‑appreciated crises—rapid loss of Midwest topsoil (from a foot to an inch), severe water shortages, and a 50‑75% drop in insect biomass—warning of their long‑term economic and ecological impacts. He details sub‑replacement fertility rates in South Korea, Japan, the US, the UK, and parts of Europe, stressing the looming demographic crunch. Grantham evaluates the Biden Climate and Tax Act as an important climate signal and a boon for his foundation’s green‑tech investments, while noting the political risk of perceived self‑interest. He characterizes the current market as a 2.5‑3 sigma “super‑bubble,” comparing it to 1929, 2000, and 2022, and argues that the US equity market is the primary over‑valued segment. He assesses the UK’s productivity slowdown, attributing it largely to Brexit and talent outflows, and notes that housing valuations are high relative to income. The conversation turns to Grantham’s early‑stage green‑tech venture investing, his view that carbon taxes are uneven globally, and his hiring philosophy that values agreeableness and cooperation. He offers optimistic forecasts for nuclear fusion (>50% chance of commercial success) and for scaling geothermal using fracking technology. Personal anecdotes about growing up in a Yorkshire coal town, early exposure to scarcity, and his path through Harvard Business School illustrate the roots of his long‑term perspective. Throughout, Grantham critiques economists for underestimating resource limits and markets for mispricing long‑term risks, emphasizing the need for proactive investment and policy to avert looming environmental and demographic challenges.

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