United Nations Charts Course to Manage Global Warming-Limit Breach

Syllabus: GS3/Environment and Ecology

Context

• The United Nations Environment Programme (UNEP) has released the Limiting Overshoot report, outlining an “overshoot, peak and decline” pathway to manage the likely temporary breach of the 1.5°C global warming limit set by the Paris Agreement.

What is the “Overshoot, Peak and Decline” pathway?

• Overshoot: Global average temperature temporarily rises above 1.5°C above pre-industrial levels.
• Peak: The increase in temperature should be kept as low as possible and the duration above 1.5°C should be minimised.
• Decline: Through deep emission reductions and large-scale carbon dioxide removal, global temperatures should subsequently be brought back below 1.5°C by the end of the century.
• UNEP describes this as not an acceptable or preferred pathway but the “best remaining option”.

Why Is Overshooting 1.5°C Becoming Likely?

• UNEP estimates that global warming could cross 1.5°C within the next few years.
• Even if all countries fully implement their Nationally Determined Contributions (NDCs) and net-zero commitments, peak warming could reach around 1.8°C.
• Current policies could result in approximately 2.6°C warming by 2100, with an estimated range of 1.9°C–3.6°C.
• Rapid depletion of the remaining global carbon budget has reduced the possibility of avoiding a temporary breach.

International Recognition of the Overshoot Challenge

• The diplomatic grounds for that framing were laid at the 30th UN Climate Change Conference, COP30, held in 2025 in Brazil’s Belém, where the consensus “Global Mutirão” decision became the first COP text to concede that a temporary overshoot of the 1.5°C threshold was increasingly likely. 
• The countries committed to:
  • Limiting the magnitude and duration of overshoot.
  • Accelerating deep and sustained emission reductions.
  • Closing existing adaptation gaps.
  • Scaling up nature-based carbon removals, including reforestation.

Why Does the Duration of Overshoot Matter?

• The UNEP report suggested that time spent above 1.5°C carries compounding costs such as faster sea-level rise, coral reef collapse, glacier loss exceeding a quarter of global mass by 2100, and declines of up to 14% in global food production by 2050.
  • Every additional five years of high emissions could add roughly 0.1°C to peak warming.
• Without effective adaptation, there is increased risk of irreversible tipping points in the West Antarctic and Greenland ice sheets, the Atlantic Meridional Overturning Circulation and the Amazon.

Role of Carbon Dioxide Removal (CDR)

• Carbon dioxide removal cannot substitute for emission reductions; it is required in addition to deep emission cuts.
• Potential approaches include:
  • Afforestation and reforestation.
  • Ecosystem and soil restoration.
  • Other technological and engineered carbon removal methods.
• The UNEP stresses that temperatures can credibly be brought back towards 1.5°C only if peak warming remains well below 2°C.
• Methane targets: The report placed significant stress on methane, which currently contributes about 0.5°C of warming. Cutting it is described as the most effective way to slow warming in the near term.
  • Over 155 countries have joined the Global Methane Pledge to cut anthropogenic methane at least 30% below 2020 levels by 2030. 

Way Ahead

• The UNEP pathway represents a shift from a strategy focused solely on avoiding 1.5°C towards managing a likely temporary breach while preventing a much more dangerous temperature trajectory.
• The longer and higher the world remains above 1.5°C, the greater the risk of irreversible ecological and economic losses and the more difficult it becomes to restore temperatures. 
• Therefore, the most effective strategy remains an “overshoot of ambition”—rapid emission reductions combined with methane mitigation, adaptation and carefully scaled carbon removal.

Source: TH