Climate change made Typhoon Gaemi more likely and more destructive: WWA study

Sea surface temperatures as warm as those in the Philippine Sea, which fuelled the intense typhoon, would have been virtually impossible without climate change, says the study

Climate change worsened the extreme winds and rainfall that were generated by Typhoon Gaemi in July, leaving more than 100 people dead and a trail of destruction through the Philippines, Taiwan and Hunan provinces of China, a rapid analysis by a team of leading scientists from World Weather Analysis (WWA) found. 

Typhoon Gaemi (known in the Philippines as Super Typhoon Carina) strengthened into a tropical storm last month on July 20th while tracking northwest towards the Philippines. Gaemi did not make landfall in the Philippines, but interacted with the ongoing southwest monsoon (known locally as Habagat), causing heavy winds and torrential rainfall from July 22-24 in the northern Philippines. In total, 48 people were killed, with around 6.5 million affected by the severe conditions. 45 landslides were triggered across the northern islands, there were power outages in over 100 cities and municipalities, and around 400 sections of road and 30 bridges were damaged.

The analysis found that Typhoon Gaemi’s wind speed was about 9 mph (14 km/h) or 7% more intense due to climate change and that climate change increased Gaemi’s rainfall by up to 14%. The warm sea surface temperatures that fueled Gaemi would have been virtually impossible without climate change, the analysis added.

Impact across Asian countries

Typhoon Gaemi swept across the Philippines, Taiwan and Hunan in late July. The typhoon dumped more than 300 mm of rainfall on Manila, the capital of the Philippines, leading to floods as deep as a one-story building in downtown areas. Gaemi’s winds reached 145 mph (233 km/h) before slamming into Taiwan. These speeds were equivalent to a Category 4 hurricane. Stormy seas sank a cargo ship near Taiwan and an oil tanker off the Philippines, causing a huge oil spill. Gaemi made a second landfall in eastern China, lashing inland regions with heavy rainfall, leading to devastating floods and landslides, notably in the Hunan Province. Overall, more than 100 people were killed by Gaemi across the three countries and hundreds of thousands were displaced.

The study, which used two attribution methodologies, found that climate change made Typhoon Gaemi both more likely and more destructive. Since 1900, there has been a 30% increase in the number of typhoons as intense as Gaemi that form in the northwest Pacific Ocean. This finding is in line with previous studies highlighting an increase in the number of the most powerful typhoons, hurricanes and tropical cyclones.

The scientists also investigated the influence of climate change on the sea surface temperatures that helped form and fuel Typhoon Gaemi. In a 1.2°C cooler world without human-caused warming, the study said, sea surface temperatures as warm as those in the Philippine Sea would have been virtually impossible.

Need to speed up emergency responses

Countries in southeast and east Asia are no stranger to typhoons with one third of tropical cyclones globally occurring in the northwest Pacific Ocean. While early warning systems and emergency responses are well established in the region, the study highlighted gaps in typhoon preparedness and the massive impacts caused by Gaemi.

Many of the deaths in the Philippines and Hunan were linked to flooding and landslides. Researchers said that improving urban flood management and targeted warnings that outline expected impacts will save lives during future typhoons, particularly in dense, rapidly growing cities.

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