New form of El Niño may increase storms in the Atlantic

The warming of the tropical Pacific Ocean has long been known to affect weather around the world, but researchers now say it may come in two forms with different impacts.

The traditional El Niño tends to reduce the number of Atlantic hurricanes. But a form Georgia Tech scientists call El Niño Modoki can lead to more hurricanes than usual in the Atlantic Ocean. Modoki, from Japanese, refers to something that is “similar but different.’’

The traditional El Niño involves a periodic warming of the water in the eastern part of the tropical Pacific. Indeed, it was first noticed by Peruvian fishermen, who named it after the baby Jesus because it tended to first appear around Christmastime.

In El Niño Modoki, on the other hand, the warming occurs farther to the west, in the central Pacific.

It is not clear why this new form is occurring, said Peter J. Webster, a professor at Georgia Tech’s School of Earth and Atmospheric Sciences and a coauthor of a report on the finding in today’s edition of the journal Science.

“It may be responding to some [climate] oscillation, or it may be in response to global warming,’’ Webster said.

Regardless of the cause, improved understanding of El Niño and its cold-water counterpart, La Niña, could help atmospheric scientists forecast weather more accurately, including the number of Atlantic hurricanes.

Traditionally, La Niña has been associated with more Atlantic hurricanes than normal and El Niño with fewer.