Unprecedented climate events: Historical changes, aspirational targets, and national commitments

Area of Science:

• Climate Science
• Extreme Weather Event Attribution

Background:

• The Paris Agreement necessitates comparing cumulative emissions impacts against national commitments and global warming targets (1.5°C–2°C).
• Human activities have demonstrably increased the frequency and intensity of extreme weather events globally.

Purpose of the Study:

• To quantify the impact of different emissions scenarios on extreme weather event probabilities.
• To assess the effectiveness of national commitments versus aspirational climate targets in mitigating climate change impacts.

Main Methods:

• Analysis of historical climate data and emissions pathways.
• Probabilistic event attribution modeling for temperature and precipitation extremes.
• Comparison of projected extreme event increases under various emissions scenarios.

Main Results:

• Human activities have already raised the probability of unprecedented hot, warm, wet, and dry extremes across North America, Europe, and East Asia.
• Emissions aligned with national commitments will significantly amplify these extremes, particularly heat and precipitation events.
• Achieving aspirational 2°C targets substantially reduces the affected areas but does not eliminate increased risks of record-setting events.

Conclusions:

• Current national climate commitments are insufficient to prevent widespread increases in extreme weather.
• Meeting aspirational global warming targets is crucial for limiting the amplification of extreme climate events.
• Even under ambitious scenarios, significant increases in the probability of record-setting weather events will persist in many regions.