03 Jun 2022
03 Jun 2022
Status: this preprint is currently under review for the journal ACP.

How extreme apparitions of the volcanic and anthropogenic south east Asian aerosol plume trigger and sustain: El Niño and Indian Ocean Dipole events; and drought in south eastern Australia. First attribution and mechanism using Global Volcanism Program, Last Millennium Ensemble, MERRA-2 reanalysis and NASA satellite data

Keith Alan Potts Keith Alan Potts
  • Kyna Keju Pty Ltd, Adelaide, 5041, Australia

Abstract. Volcanic aerosols over south east Asia (SEAsia), and only over SEAsia, have always been the trigger and sustaining cause of: El Niño/Southern Oscillation (ENSO) events which are the dominant mode of variability in the global climate responsible for Australian, Indian and Indonesian droughts, American floods and increased global temperatures; and Indian Ocean Dipole (IOD) events. In recent decades this natural plume has been augmented by an anthropogenic plume which has 25 intensified ENSO events especially from September to November. Understanding the mechanism which enables aerosols over SEAsia, and only over SEAsia, to create ENSO events is crucial to understanding the global climate. I show that the SEAsian aerosol plume causes ENSO events by: reflecting/absorbing solar radiation which warms the upper troposphere; and reducing surface radiation which cools the surface under the plume. This inversion reduces convection in SEAsia thereby suppressing the Walker Circulation and the Trade Winds which causes the SST to rise in the central Pacific Ocean 30 and creates convection there. This further weakens/reverses the Walker Circulation driving the climate into an ENSO state which is maintained until the SEAsian aerosols dissipate and the climate system relaxes into a non-ENSO state. Data from the Global Volcanism Program (151 years), the Last Millennium Ensemble (1,156 years), MERRA-2 (41 years) and NASA MODIS on Terra (21 years) demonstrates this connection with the Nino 3.4 and 1+2 SST, the Southern Oscillation Index, and two events commonly associated with ENSO: drought in south eastern Australia; and the IOD.

Keith Alan Potts

Status: open (until 27 Jul 2022)

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Keith Alan Potts


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Short summary
El Niño events, the greatest inter-annual variation in the global climate, are and always have been caused by volcanic aerosols in south east Asia. Recently the volcanic aerosols have been augmented by anthropogenic aerosols especially 15 from September to November which has intensified ENSO events. The same aerosol plume also creates drought in south eastern Australia and Indian Ocean Dipole events simultaneously. Volcanic, modelling, reanalysis and measured data all show the same results.