A new academic study is challenging one of the most comfortable assumptions in climate policy: that generous incentives alone can deliver deep cuts in greenhouse gas emissions. Researchers from the University of California San Diego and Princeton University modeled what happens when governments combine subsidies for clean energy with taxes or fees on greenhouse gas pollution.
“This work helps make our climate models more realistic about how governments actually behave. For years, models have told us what’s economically efficient—but not what’s politically possible. Our goal is to bridge that gap so policymakers can craft strategies that survive real-world politics.” said the study’s co-author David Victor, professor at the School of Global Policy and Strategy and co-director of UC San Diego’s Deep Decarbonization Initiative (D2I).
Their conclusion is blunt. Incentives can drive rapid adoption of cleaner technologies early on, but without pricing for carbon and methane emissions long-term decarbonization stalls.
The work, published in Nature Climate Change, breaks new ground by simulating policy mixes that more closely resemble how governments actually behave. Most economic models still assume a single, economy-wide carbon price, even though few countries have ever adopted one. The new modeling instead tests sequences of incentives, penalties and political reversals across all 50 U.S. states through 2050.
The results suggest that stable subsidies for electric vehicles, renewable power and clean manufacturing can sharply reduce emissions in the near term by lowering costs and speeding deployment. But the biggest gains come when those carrots are later paired with sticks that make fossil fuels progressively more expensive.
Timing also matters. When incentives are delayed, repealed or restarted, investment slows and emissions cuts later become more costly. Consistent policy, the study finds, can put the energy system on track for roughly an 80% reduction in emissions by mid-century.
The findings arrive as U.S. climate policy faces renewed uncertainty. Clean energy tax credits enacted under the Inflation Reduction Act are under political pressure, while a federal carbon tax remains off the table. That stands in contrast to Europe, where emissions trading has steadily tightened, and China, which is expanding both clean energy subsidies and carbon pricing mechanisms.
International agencies such as the International Energy Agency have similarly warned that subsidies alone cannot deliver net-zero goals without measures that discourage continued fossil fuel use. The new research adds modeling evidence to that broader global debate, underscoring that climate success depends not just on ambition, but on durable policy design that survives real-world politics.
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