HONG KONG—As El Niño reaches its peak this winter, investors are already bracing for its sister climate phenomenon, La Niña, to be next to upend weather patterns and potentially wreak havoc on the agricultural commodity market. Government forecasters in Australia and Japan have in recent weeks said the current El Niño may already have peaked and will ease through the first half of 2016 as temperatures cool on the subsurface of the eastern Pacific Ocean. By the start of December, this year’s El Niño—the strongest since 1997-1998—had caused sea surface temperatures to rise by more than 3.6 degrees Fahrenheit in places, and driven a rally in agricultural commodities such as palm oil, sugar and dairy. The end of an El Niño event is often followed by the reversal of the phenomenon, known as La Niña, although that isn’t a given. While El Niño and its impact might be better […]