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Abstract Changes in rainfall variability of El Niño–Southern Oscillation (ENSO) are investigated under scenarios where the greenhouse gases increase and then stabilize. During the period of increasing greenhouse forcing, the ocean mixed layer warms rapidly. After the forcing stabilizes, the deeper ocean continues to warm the surface (the slow response). We show that ENSO rainfall variability over the tropical Pacific intensifies in both periods but the rate of increase per degree global mean surface temperature (GMST) warming is larger for the slow response because of greater relative warming in the base state as the mean upwelling changes from a damping to a driver of the surface warming. Our results have important implications for climate extremes under GMST stabilization that the Paris Agreement calls for. To stabilize GMST, the fast surface cooling offsets the slow warming from the prior greenhouse gas increase, while ENSO rainfall variability would continue to increase.
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Enhanced El Niño–Southern Oscillation Variability in Recent Decades
Abstract The El Niño–Southern Oscillation (ENSO) represents the largest source of year‐to‐year global climate variability. While Earth system models suggest a range of possible shifts in ENSO properties under continued greenhouse gas forcing, many centuries of preindustrial climate data are required to detect a potential shift in the properties of recent ENSO extremes. Here we reconstruct the strength of ENSO variations over the last 7,000 years with a new ensemble of fossil coral oxygen isotope records from the Line Islands, located in the central equatorial Pacific. The corals document a significant decrease in ENSO variance of ~20% from 3,000 to 5,000 years ago, coinciding with changes in spring/fall precessional insolation. We find that ENSO variability over the last five decades is ~25% stronger than during the preindustrial. Our results provide empirical support for recent climate model projections showing an intensification of ENSO extremes under greenhouse forcing.
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- Award ID(s):
- 1634996
- PAR ID:
- 10455120
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 47
- Issue:
- 7
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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