Leading climate scientists have revised the worst-case projection for global warming by the end of the century, lowering it from 4.5°C to 3.5°C above pre-industrial levels. The update, part of the Scenario Model Intercomparison Project (ScenarioMIP), reflects the accelerating impact of cheap renewable energy and stronger climate policies in curbing emissions.
The new models, which will feed into future assessments by the Intergovernmental Panel on Climate Change (IPCC), incorporate real-world emissions data up to 2023, extending beyond the 2015 cutoff used in previous scenarios. They also better capture how Earth's systems—such as ocean and forest carbon absorption—respond to warming.
Why the worst-case scenario has shifted
The plummeting cost of solar and wind energy has made a future dominated by fossil fuels increasingly implausible. According to the ScenarioMIP team, the previous worst-case scenario assumed that renewable energy costs would stop falling, possibly due to mineral shortages or trade disputes. But the sustained decline in solar and wind prices has undercut that assumption, pushing the upper temperature limit down by 1°C.
Still, the revised worst-case projection of 3.5°C remains far above the 2°C target set by the 2015 Paris Agreement, and even further from the preferred 1.5°C limit. Such warming would trigger irreversible changes in slow components of the Earth system, including deep ocean currents, ice sheets, and glaciers, with catastrophic consequences for sea levels and ecosystems.
The models also envision a scenario where climate policies weaken or reverse, fossil fuel use rises beyond current reserves, and international cooperation collapses amid resurgent nationalism and regional conflicts. In that case, emissions would spike, locking in long-term damage.
Alternative pathways and European implications
ScenarioMIP also models milder futures. If current policies continue unchanged, preliminary estimates suggest warming of around 2.5°C. Delayed but eventual net-zero by 2100 could limit warming to 2°C. The most ambitious scenarios, aiming for net-zero as quickly as possible, still foresee an unavoidable overshoot of 1.5°C, with lasting harm to coral reefs and rainforests.
For Europe, the stakes are high. The continent has been a leader in renewable energy deployment, with countries like Germany, Spain, and Denmark driving down solar and wind costs. The European Union's Green Deal and national policies in member states such as France and the Netherlands have contributed to the emissions reductions that underpin the revised projections. However, the models warn that a lack of cooperation—or a shift toward domestic priorities—could undermine progress.
As solar panel prices may rise due to supply chain pressures, the window for cost-effective investment in renewables remains open. European policymakers and businesses are urged to maintain momentum, as further delays could lock in higher warming pathways.
Further Earth System Model simulations, including carbon cycle feedbacks, are planned later this year and could alter the projections. For now, the revised worst-case offers a glimmer of hope—but underscores that even the best-case scenarios carry serious risks.
