Niño 3.4 sea-surface temperature tracker

Range of prior years (min–max)   Middle 80% of prior years

Range of prior years (min–max)   Middle 80% of prior years

Interpretation

Anomaly = daily SST minus the 1991–2020 daily mean. Recent values are preliminary and may be revised by NOAA. Not the relative index NOAA uses to classify El Niño strength. Data: NOAA OISST v2.1, provided by the NOAA PSL, Boulder, Colorado, USA, from their website at psl.noaa.gov.

El Niño and the hurricane seasons

El Niño warms the eastern and central Pacific and changes the winds high over the Atlantic. That usually makes the Pacific hurricane season busier and the Atlantic season quieter; La Niña tends to do the opposite. The charts add up each season's accumulated cyclone energy (ACE), which counts every storm by how strong it was and how long it lasted, so one long-lived major hurricane weighs far more than several short tropical storms.

Range of prior years (min–max)   Middle 80% of prior years

Range of prior years (min–max)   Middle 80% of prior years

Most of the swing from one season to the next comes from El Niño, La Niña and other natural patterns, and the yearly totals show no clear long-term trend. Warming shows up in how storms behave instead: a larger share become the most intense, they strengthen faster and they bring more rain (see Hurricanes aren't getting worse). ACE = sum of the squared maximum wind (knots) every 6 hours while a storm is at least a tropical storm (34 kt), divided by 10,000. Northeast Pacific includes the central Pacific up to the date line. Data: NOAA NCEI IBTrACS v04r01, with NHC's operational data for the current season, which is replaced by best-track data after review.

El Niño over 900 years

Thermometers measure the Niño 3.4 region since the 1870s. Before that, tree rings fill in: El Niño changes rain and drought around the Pacific (the southwestern US, Mexico, Indonesia), and old trees record those wet and dry years in the width of their rings. Cook and Cane (2024) used this to rebuild the Pacific's winter sea-surface temperature back to the year 1100. Below, every winter since then, with the measured winters on top.

Each value is the December–February average over the Niño 3.4 box (5°S–5°N, 170°W–120°W), compared with the measured 1871–2000 average. Tree rings: Cook and Cane (2024), the version with more tree-ring records (from 1500) and the longer one before that; each reconstructed winter has an error of about ±0.5 °C, and like most reconstructions it tends to understate the largest events. Measured: the gridded sea-surface temperatures that come with the reconstruction (1871–1981), then NOAA OISST (from 1982), shifted to the same reference using the winters both cover (1983–2000). A winter average is lower than the peak month of the same event. Data: Cook, E.R. and Cane, M.A. (2024), Tree Rings Reveal ENSO in the Last Millennium, Geophysical Research Letters, doi:10.1029/2024GL109759, via NOAA NCEI Paleoclimatology.