evidence: Though El Niño is not caused by climate change, it often produces some of the hottest years on record because of the vast amount of heat that rises from Pacific waters into the overlying atmosphere. Major El Niño events—such as 1972-73, 1982-83, 1997-98, and 2015-16—have provoked some of the great floods, droughts, forest fires, and coral bleaching events of the past half-century. [...] When deciding whether the Pacific is in an El Niño state, the climatologists at NOAA examine sea surface temperatures in the east-central tropical Pacific—referred to as the Niño 3.4 region (between 120° to 170° West). An El Niño is declared when the average temperature stays more than 0.5 degrees Celsius above the long-term average for five consecutive months. In 1997-98 and 2015-16, sea surface temperatures rose more than 2.5 degrees Celsius (4.5 degrees Fahrenheit) above the average. [...] El Niño is the largest natural disruption to the Earth system, with direct impacts across most of the Pacific Ocean. Indirect impacts reverberate around the globe in patterns that scientists refer to as "teleconnections." Scientists are actively trying to understand how these changes in weather patterns in one area can alter the movement of air masses and winds in areas adjacent to and even far away from the source. According to the International Research Institute for Climate and Society at Columbia University, El Niño-Southern Oscillation is responsible for as much as 50 percent of year-to-year climate variability in some regions of the world.