Mauna Loa carbon dioxide forecast for 2026
. the Niño3.4 index for April of the preceding year to March of the current year. The Niño3.4 index is the sea surface temperature (SST) anomaly in region 5°N to 5°S and 170°W to 120°W in the Pacific Ocean, de-trended to remove the effect of long-term warming. For short periods such as individual years