A joint study by World Weather Attribution and Climate Central found that climate change and El Nino combined to strengthen Hurricane Polo, the longest-lasting Category 5 storm ever recorded in the Pacific, with human-caused warming playing the larger role.
The study, published Thursday, found that global warming from burning coal, oil and gas added about 6 mph (nearly 10 kph) to the storm's strength, while El Nino contributed about 5 mph (8 kph), according to AP reporting on the research. Climate change made the conditions that fuelled the hurricane 23 times more likely, while El Nino made them 14 times more likely.
The researchers linked the intensification to exceptionally warm ocean waters of 88 degrees Fahrenheit (31.2 degrees Celsius), as much as 3.6 degrees Fahrenheit (2 degrees Celsius) above normal. Polo rapidly strengthened from a tropical depression on 20 September to a Category 5 hurricane within about 24 hours, according to the World Weather Attribution summary, and spent about two and a half days at Category 5 strength — a Pacific record.
Polo made landfall in Baja California Sur on 28 September as a Category 2 hurricane, before reaching mainland Mexico east of Guaymas on 29 September as a Category 1 hurricane. The storm stalled for several days, fluctuating between Category 4 and Category 5 strength, which gave residents more time to prepare.
Study co-author Friederike Otto, who coordinates the World Weather Attribution team, said both El Nino and climate change made the hurricane stronger than it would otherwise have been, but the climate change effect was even bigger. She said El Nino comes and goes, but climate change only worsens, meaning every hurricane in the East Pacific now carries at least this climate-change signal. The researchers also found that Polo would have been a powerful storm even without warming or El Nino, but added wind speed can greatly amplify destruction.