Thresholds of catastrophe in the Earth system

Area of Science:

• Earth system science
• Paleoclimatology
• Geochemistry

Background:

• Earth's history is marked by both gradual changes and abrupt, destructive mass extinctions.
• Understanding the triggers for catastrophic events is crucial for predicting future risks.

Purpose of the Study:

• To hypothesize and test the conditions under which carbon cycle perturbations lead to mass extinctions.
• To identify critical thresholds for carbon cycle changes in Earth's history.

Main Methods:

• Analysis of 31 carbon isotopic events over the past 542 million years.
• Application of mass conservation principles to define critical rates.
• Identification of a crossover timescale to determine critical size thresholds.

Main Results:

• Established a critical rate limit for carbon cycle perturbations based on mass conservation.
• Determined a critical size threshold for short-timescale events.
• Found that the modern marine carbon cycle's critical size is similar to projected anthropogenic carbon additions by 2100.

Conclusions:

• Carbon cycle perturbations exceeding critical rates or sizes are linked to mass extinctions.
• The identified thresholds provide a framework for assessing extinction risks.
• Current human activities pose a significant risk to the marine carbon cycle, potentially nearing a critical threshold.