A Deadly Combo
Following the 1997-98 El Niño event, 15 percent of the world's coral reefs died. Many scientists suspect that El Niño was not the sole culprit but was aided by global warming. During the past 100 years, sea temperatures have increased, causing many corals to live close to the maximum temperature they can withstand. An El Niño event increases the sea temperature even more.
In 1994 living coral tissue covered this entire 400-year-old coral formation near Key West, Florida (top). By 1998, over 75% of this colony had died due to a rise in sea temperatures (bottom).