For decades, scientists watched temperatures in the Pacific Ocean swing back and forth like the needle on a metronome.
It’s a recurring climate cycle known as the Pacific Decadal Oscillation, or PDO. Often regarded as a kind of long-lasting El Niño event, the cycle causes the waters to grow warmer or cooler for years at a time, influencing weather patterns along the North American coast.
Until now, scientists believed the PDO was driven mainly by natural variations in the climate system. But new research has turned that theory on its head.
A study published Wednesday in the prestigious scientific journal Nature finds that human pollutants have had a major influence on the PDO for at least 70 years. Between 1950 and 1980, aerosols from industrial activities were the main driver. And since the 1980s, greenhouse gas emissions have taken the dominant role.
