Decreasing global tropical cyclone frequency in CMIP6 historical simulations

Area of Science:

• Climate Science
• Atmospheric Science
• Meteorology

Background:

• Assessing the impact of anthropogenic global warming on tropical cyclone (TC) frequency is challenging due to limited observational data and model discrepancies.
• Understanding historical TC trends is crucial for climate change impact assessments.

Purpose of the Study:

• To investigate the impact of global warming on historical tropical cyclone frequency using climate model simulations.
• To identify the physical mechanisms driving changes in TC frequency.

Main Methods:

• Analysis of tropical cyclone detection from 20 Coupled Model Intercomparison Project Phase 6 (CMIP6) historical simulations.
• Examination of atmospheric circulation patterns and thermodynamic variables within the models.

Main Results:

• A majority (75%) of CMIP6 models simulate a decrease in global TC frequency from 1850 to 2014.
• Weakened mid-tropospheric upward motion in key TC development regions (Pacific, Atlantic) is a primary driver.
• Reduced TC frequency in the South Indian Ocean is linked to increased saturation deficit, affecting storm survival.

Conclusions:

• Global warming is a significant factor potentially explaining the observed historical decrease in global TC frequency.
• Changes in atmospheric circulation and thermodynamics are key mechanisms influencing TC activity under climate change.