Earth's 5th Costliest Non-U.S. Weather Disaster on Record: China's $22 Billion Flood

A historic flood event continues in China, where torrential monsoon rains along the Yangtze River Valley in central and eastern China since early summer have killed 237 people, left 93 people missing, and caused at least $22 billion in damage, the Office of State Flood Control and Drought Relief Headquarters said on Thursday. According to the International Disaster database, EM-DAT, this would make the 2016 floods China's second most expensive weather-related natural disaster in history, and Earth's fifth most expensive non-U.S. weather-related disaster ever recorded. Only China's 1998 floods, with a price tag of $44 billion (2016 dollars), were more damaging than the 2016 floods. According to the June 2016 Catastrophe Report from insurance broker Aon Benfield, Earth's only deadlier weather disaster in 2016 was an April heat wave in India that claimed 300 lives. Some 147,200 houses have been destroyed by this summer's floods in China, and over 21,000 square miles of farmland had been inundated--an area the size of Massachusetts and Vermont combined. An additional $1.3 billion in flood damage from Typhoon Nepartak occurred in China in July.


Figure 1. A stadium in Wuhan, China on July 6, 2016, after the city received 7.09” (180 mm) of rain in the twelve hours ending at 8 am July 6. Wuhan received over 560 mm (1.8 feet) of rain over the ten day period before the July 6 deluge, causing widespread damage and chaos. (Photo by Wang He/Getty Images)


Figure 2. Flood waters inundate a village in Xuancheng, in east China's Anhui province, on July 7, 2016. Image credit: STR/AFP/Getty Images.

Monsoon season in China
It's been a severe monsoon season in China this year. As we noted in a June 23 post, the heavy rains in China have occurred along the Mei-yu (or baiu) front, a semi-permanent feature that extends from eastern China across Taiwan into the Pacific south of Japan, associated with the southwest monsoon that pushes northward each spring and summer. The Mei-yu rains typically affect Taiwan and southeastern China from mid-May to mid-June, then migrate northwards to the Yangtze River region and southern Japan during June and July (the Mei-yu is known as Baiu in Japan), and then further northward to northern China and Korea (known as Changma in Korea) during July and August. A number of studies have found that the Mei-yu rainfall tends to be particularly heavy in the summer following an El Niño event, as is occurring in 2016--and occurred in 1998, the only year to experience more damaging flooding in China.


Figure 3. This summer's floods in China are the fifth most expensive weather-related natural disaster on record outside of the U.S., according to the International Disaster database, EM-DAT.


Figure 4. The U.S. has seen twelve weather-related disasters costing at least $20 billion, with eleven of them more expensive than the 2016 Chinese floods. Data source: NOAA/NCEI.

Heavier Mei-yu rains are expected in a warming climate
As the planet’s oceans and atmosphere warm up due to increased amounts of heat-trapping gases like carbon dioxide, more water vapor is entering the lower atmosphere, which provides more fuel for heavy rain. Observations show that the heaviest periods of precipitation have become more intense in many parts of the globe, and climate models agree that this trend should continue as our planet continues to warm. The Yangtze Valley of China is among the locations where a significant increase in summer precipitation was found to occur during the 20th century, as described in a 2007 paper in the International Journal of Climatology. A multiyear series of studies using high-resolution global circulation models (20 km), led by Shoji Kusunoki (Japan’s Meteorological Research Institute, or MRI) and colleagues, found that both average and extreme precipitation in the Mei-yu zone will increase during the 21st century (see this 2011 paper in Climate Dynamics). Subsequent modeling has only strengthened this finding. In the 2015 book “The Monsoons and Climate Change: Observations and Modeling,” Hirokazu Endo (MRI) and Akio Kitoh (University of Tsukuba, Japan) conclude: “State-of-the-art climate models project that both the amount and intensity of Asian summer monsoon rainfall are likely to increase under global warming, and that the rates of increase will be higher than those in other monsoon regions…Considering the improvements in CMIP5 (climate models) compared to CMIP3 in simulating present-day characteristics, we now have more confidence in future projections.”


Figure 5. Rainfall for the 30-day period ending on July 14, 2016 over China. Rainfall amounts in excess of 15.75" (400+ mm, dark blue color) fell over a large swath of the Yangtze River basin in China from Wuhan to just west of Shanghai. Image credit: National Meteorological Center of CMA.


Figure 6. Predicted total precipitation over China for the 16-day period ending at 00 UTC July 31, 2016, from the 00 UTC Friday, July 15, 2016 run of the GFS model. A wide swath of 12+" (305 mm) monsoon rains (light orange colors) is predicted to fall over portions of the Yangtze River basin. Image credit: tropicaltidbits.com.

More damaging flooding to come this summer in China
The flooding damage in China is likely to grow this month, as new rounds of torrential monsoon rains hit the nation in the coming weeks. "Although the water levels in middle and lower reaches of the Yangtze River are slowly dropping, most are still above warning levels," Zhang Jiatuan, a spokesperson for the Office of State Flood Control and Drought Relief Headquarters, told reporters on Thursday. He said the situation was "still quite critical" as central and eastern parts of China are expected to see a fresh round of heavy rain over the days to come. The latest precipitation forecast from the GFS model predicts a wide swath of 12+" of rain will fall over much of the flood-affected area through the end of July (Figure 6.)

Jeff Masters and Bob Henson