UNEP Says 1.5°C Overshoot Is Now Difficult to Avoid and Must Be Governed in Three Phases

UNEP divides the outlook into pre-overshoot, peak-warming and decline phases, requiring mitigation, adaptation and carbon removal to be governed differently in each. The report says the most ambitious feasible pathway may still peak near 1.8°C, while current policies imply median warming of about 2.6°C by 2100.

UNEP divides the outlook into pre-overshoot, peak-warming and decline phases, requiring mitigation, adaptation and carbon removal to be governed differently in each. The report says the most ambitious feasible pathway may still peak near 1.8°C, while current policies imply median warming of about 2.6°C by 2100. Carbon removal may support a later decline, but land, water, ecosystem, permanence and reversal risks mean it cannot replace deep near-term emissions cuts.

A single 2100 temperature endpoint can hide peak magnitude and duration. Corporate net-zero plans may also treat future removals as certain assets while overlooking maturity, resource competition, storage risk and irreversible damage during overshoot.

Policy and corporate scenarios should report near-term reductions, peak warming, years above threshold, adaptation gaps, removal type and failure sensitivity. Investment decisions need phase-specific triggers rather than a single net-zero year.

Evidence chain: Carbon removal may support a later decline, but land, water, ecosystem, permanence and reversal risks mean it cannot replace deep near-term emissions cuts.

Overshoot governance raises the accountability threshold for long-term scenarios. Financial institutions and high-emitting sectors need to disclose pathways, residual emissions, removal dependence and physical risk rather than presenting one smooth decline curve.

SNN editorial analysis: Taiwan semiconductor, electronics, petrochemical, steel, power and financial institutions often communicate transition through 2030 or 2050 endpoints, but overshoot requires time-resolved evidence. Pre-Disclosure Evidence Infrastructure should retain base-year emissions, annual budgets, scenario-model versions, temperature assumptions, site physical risk, adaptation actions, residual emissions, removal-project identity, delivery timing, permanence and reversal monitoring. Every target change should trace to new science or operating data. Taiwan companies should distinguish internal target, contracted action, delivered reduction and dependence on future removals, preventing a 2050 endpoint from obscuring a near-term gap. This is editorial interpretation, not a source-verified fact.

Next review should test execution milestones, updated measurements, methodology changes, adverse outcomes and whether the evidence supports each public claim. Material changes must create a new version rather than overwrite this record.