El Niño - Comparing 1997 to 2015

These images were created using data collected by the TOPEX/Poseidon satellite and the Ocean Surface Topography Mission/Jason-2 satellite. The colors indicate differences in sea surface height, which reflect differences in temperature. Higher areas (red and white) are warmer. Lower areas (pink and purple) are colder. 

The red band cutting across the Pacific indicates an El Niño, the warming of waters in the tropical Pacific. An El Niño occurs every three to seven years and is linked to changes in air pressure and high-level winds. It affects weather worldwide and normally develops during March-June, reaches peak intensity during December-April, and then weakens during May-July. 

The 1997-98 El Niño is the strongest on record and 2015's is just as strong.