Well below 2 °C: Mitigation strategies for avoiding dangerous to catastrophic climate changes

Area of Science:

• Climate Science
• Environmental Policy
• Risk Assessment

Background:

• The Paris Agreement aims to limit global temperature rise to well below 2 °C.
• Uncertainties in climate models necessitate a risk-based approach to warming.
• Existing risk categories for warming are insufficient for high-impact scenarios.

Purpose of the Study:

• To define new climate risk categories including low-probability, high-impact (LPHI) warming.
• To outline a strategy to mitigate both central and LPHI warming scenarios.
• To inform policy decisions for near-term and long-term climate action.

Main Methods:

• Categorization of climate risks based on temperature thresholds (>1.5 °C dangerous, >3 °C catastrophic, >5 °C unknown).
• Analysis of warming projections under unchecked emissions scenarios.
• Development of a three-lever mitigation strategy: Carbon Neutral (CN), Super Pollutant (SP), and Carbon Extraction and Sequestration (CES).

Main Results:

• Central warming may reach dangerous levels within three decades without intervention.
• LPHI warming could become catastrophic by 2050 under current emission trends.
• A combined CN and SP strategy can limit central warming; CES is crucial for LPHI mitigation.

Conclusions:

• Achieving carbon neutrality and reducing super pollutants are essential for near-term climate stabilization.
• Significant carbon extraction (1 trillion tons by 2100) is required to limit LPHI warming.
• A comprehensive strategy involving CN, SP, and CES is vital to meet Paris Agreement goals and avert existential threats.