Attribution of Extreme Weather Events in the Context of Climate Change

This volume examines the current state of science of extreme weather attribution, and identifies ways to move the science forward to improve attribution capabilities.


As climate has warmed over recent years, a new pattern of more frequent and more intense weather events has unfolded across the globe. Climate models simulate such changes in extreme events, and some of the reasons for the changes are well understood. Warming increases the likelihood of extremely hot days and nights, favors increased atmospheric moisture that may result in more frequent heavy rainfall and snowfall, and leads to evaporation that can exacerbate droughts.

Even with evidence of these broad trends, scientists cautioned in the past that individual weather events couldn't be attributed to climate change. Now, with advances in understanding the climate science behind extreme events and the science of extreme event attribution, such blanket statements may not be accurate. The relatively young science of extreme event attribution seeks to tease out the influence of human-cause climate change from other factors, such as natural sources of variability like El Niño, as contributors to individual extreme events.

Event attribution can answer questions about how much climate change influenced the probability or intensity of a specific type of weather event. As event attribution capabilities improve, they could help inform choices about assessing and managing risk, and in guiding climate adaptation strategies.

Contents
Preface
GLOSSARY
SUMMARY
Event Attribution Approaches
Assessment of Current Capabilities
Presenting and Interpreting Extreme Event Attribution Studies
The Path Forward
Concluding Remarks
1 INTRODUCTION
Why Investigate the Causes of Extreme Events?
Overview of Extreme Event Attribution Research
This Study and the Committee’s Approach
Report Road Map
2 FRAMING
General Considerations
Conditional Attribution
Use of Background Knowledge About Climate Change
Other Factors Affecting Impacts of Extreme Events
Guidance for Framing Event Attribution Questions
3 METHODS OF EVENT ATTRIBUTION
Methods Based on Observations
Methods Based on Climate and Weather Models
Uncertainties in Model-Based Studies
Uncertainty Quantification
The Use of Multiple Methods
Rapid Attribution and Operationalization
Guidance for Increasing the Robustness of Event Attribution
4 ATTRIBUTION OF PARTICULAR TYPES OF EXTREME EVENTS
Extreme Cold Events
Extreme Heat Events
Droughts
Extreme Rainfall
Extreme Snow and Ice Storms
Tropical Cyclones
Extratropical Cyclones
Wildfires
Severe Convective Storms
Challenges and Opportunities for Attribution of Particular Types of Extreme Events
5 CONCLUSIONS
Assessment of Current Capabilities
Presenting and Interpreting Extreme Event Attribution Studies
The Path Forward
REFERENCES
APPENDIXES
A Statement of Task
B Workshop Agenda
C Committee Mini Biographies