Will Climate Change Supercharge El Niño? What the IPCC Actually Says

Every strong El Niño prompts the same question: is global warming making these events worse? It is a fair question with an unsatisfying-sounding but genuinely important answer — parts of it are settled, parts are wide open, and knowing which is which matters more than any single headline. The most authoritative synthesis remains the IPCC's Sixth Assessment Report (AR6), and its verdict is worth unpacking carefully.

What the record shows so far

Start with the past. ENSO amplitude — the size of the swings between warm and cool phases — and the frequency of strong events have been higher since 1950 than during 1850-1950. On its face that sounds like a warming fingerprint. But AR6 adds essential context: reconstructions spanning the Holocene show that ENSO has waxed and waned on its own across centuries and millennia, and the recent behavior sits within that natural range. As NOAA's ENSO Blog summarizes the assessment, there is "no clear evidence that any changes since 1950 in ENSO are all that unusual."

This is not a claim that greenhouse warming has no effect on ENSO — it is a statement about detectability. Against a naturally noisy oscillation observed carefully for barely a century, a modest forced change simply cannot yet be distinguished from the system's own wandering.

The open question: future amplitude

Will ENSO's ocean-temperature swings grow, shrink, or hold steady as the planet warms? Here AR6 is blunt: climate models disagree, and there is no consensus on the sign of the change. The formal assessment is low confidence in any projected change in ENSO sea surface temperature variability.

That said, the question is under active attack. Some studies suggest the swings will grow: Cai and colleagues argued in a 2022 Nature Climate Change paper that ENSO SST variability increases under all four emission scenarios they examined. It is a serious result from a prominent group — but it is one line of evidence in a contested area, not a consensus. The appropriate posture is the one the IPCC takes: watch this space.

The robust result: wetter swings

Now for the firm ground, and it involves a different variable. AR6 finds it "very likely" that ENSO-related rainfall variability over the east-central tropical Pacific increases significantly by the second half of the 21st century under the SSP2-4.5, SSP3-7.0, and SSP5-8.5 scenarios — regardless of what happens to the SST swings.

How can rainfall variability rise even if ocean-temperature variability doesn't? Two pieces of physics. First, warmer air holds about 7% more moisture per degree Celsius — so the same ENSO-driven shift in circulation moves more water, wringing heavier rain from El Niño's wet anomalies and deeper deficits from its dry ones. Second, the eastern Pacific is projected to warm faster than surrounding waters, making it easier for deep convection to ignite there. The thermostat may swing no harder, but each swing sloshes a fuller bucket.

Consistent with this, AR6 projects that the frequency of extreme El Niño and La Niña events — defined by their precipitation impacts — will increase.

Same events, hotter stage

There is a third layer, independent of whether ENSO itself changes at all: every future event will play out on a hotter baseline. An El Niño's temporary global temperature spike — the 0.1-0.2°C boost discussed in our teleconnections article — now stacks on decades of accumulated greenhouse warming, which is why post-El Niño years like 1998, 2016, and the aftermath of 2023-24 keep setting global records. El Niño droughts arrive in regions already drier and hotter; El Niño deluges fall on a landscape already primed for heavier extremes. Even a perfectly unchanged ENSO would deliver worsening impacts on a warming planet.

And ENSO is not going anywhere. AR6 states plainly that ENSO will remain the dominant mode of interannual variability in a warmer world. The oscillation described throughout our science series is a permanent feature of the forecast landscape, not a casualty of climate change.

How to read the next headline

When a study claims El Niño will double, vanish, or permanently install itself, place it on the three-layer map:

Most headline disagreements dissolve once you notice which layer a given study addresses. The uncertainty about amplitude is real and honestly reported; the confidence about rainfall extremes and the hotter stage is equally real. Both can be true — and both are.