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What caused the devastating floods in China, India and Bangladesh?

What caused the devastating floods in China, India and Bangladesh?

In central and southern China, tens of thousands of people have been forced to evacuate their homes due to flooding caused by extreme rainfall. The Guardian reports Nearly a million people have had their homes destroyed and their lives uprooted by the worst flooding in decades.

at the same time, CNN reports In India and Bangladesh, torrential rains caused floods and landslides, devastated communities and killed more than 100 people. Flooding in northeastern Bangladesh has reportedly left 4 million people trapped, including 1.6 million children. UNICEF.

For journalists: A list of climate school experts who specialize in extreme rainfall and flooding.

State of the Earth Commentary from several experts at Columbia University’s School of Climate was gathered to learn more about the meteorological conditions behind these tragic disasters, how climate change is leading to greater downpours, and how societies are adapting to an increasingly submerged world.

flood factor

Mingfang TingA research professor at the Lamont-Doherty Earth Observatory at the Columbia Climate Institute, who studies extreme precipitation. She pointed to several large-scale climatic conditions that could lead to heavy rainfall in China and South Asia:

“I didn’t have a chance to investigate the weather conditions that led to the downpour, but since we’re in the middle of the downpour monsoon season There, a lot of rain is expected at this time of year. The question is, why is the intensity so strong? the girl Definitely one of the culprits here. During La Niña, the oceans in the western tropical Pacific, or warm pool, warm, allowing more warm, moist air to be transported to southern China when weather systems align.Another potential contributor is Indian Ocean Dipolecurrently in a slightly negative phase, which also makes the western tropical Pacific warmer than normal.

“The same concept applies to Bangladesh and northeastern India, which also experienced flooding this year. However, the negative phase of the Indian Ocean Dipole actually suppresses monsoon rainfall in central India, although La Niña does increase Indian monsoon rainfall, similar to monsoons in China and Bangladesh.”

In addition to these natural climate patterns, Ding believes that China’s recent improvement in air quality could also lead to heavy rains due to fewer aerosol particles.Although these particles harmful to human health,

“The role of aerosols is to reduce rainfall and keep clouds in the atmosphere rather than settling down, so clearing the air would have the opposite effect, increasing rainfall intensity. In terms of the anthropogenic component of rainfall intensity in recent years, the fairly successful air quality improvements likely Make flooding worse in unexpected ways.”

Contribution to climate change?

Kay CohenhuberThose who study extreme weather at the Lamont-Doherty Earth Observatory say the extreme rainfall and flooding events are consistent with what scientists expect and have observed in a climate-changing world:

“Although the exact meteorological conditions of this particular event require further investigation, the first-order physical relationship between warmer planets and more extreme rainfall is well known: Since warmer air can hold more moisture, more Extreme rainfall.

“The current flood event is yet another sad example of a series of record-setting extreme precipitation events such as the Central European floods and last year’s Hunan floods. My colleagues and I describe these events in our recent paper Sustainable development of natural cities and in Comment In The State of the Planet. “

Coincidental worry

Of particular concern, Kornhuber added, is that extreme weather events like this one are happening more closely in space and time:

“Several flooding in 2021 already occurred in parts of the areas affected by the current floods, almost simultaneously with floods in Bangladesh and India, and extreme and record high temperatures in North America, Western Europe, the Middle East and East Asia. Sequential and simultaneous Extreme scenarios can slow and suppress recovery, and could have implications for supply chains and food security. These impacts could be compounded with other unresolved crises, such as Russia’s war of aggression in Ukraine and the COVID-19 pandemic.”

people on boat on city street

Flood relief teams provide assistance in Chennai, India, during floods in November 2021. photo: Indian Navy

Likewise, Ting added that southern China has been experiencing drought in recent years, complicating matters:

“Such extreme swings can make flooding more dangerous because it’s more likely to lead to landslides. Any adaptation or solution must be able to cope with more extreme swings, like we’re seeing now, which may be ahead of them not in the plan.”

Economic and Supply Chain Considerations

In 2018, Anders Liverman Potsdam Institute for Climate Impact Research and Lamont-Doherty Earth Observatory Co-authored a study Climate-related flooding found not only affects people’s lives, but also harming the economy on a global scale. Through supply shortages, changes in demand and related price signals, economic losses can be passed downstream along global trade and supply networks, affecting other economies worldwide

The study predicts that China will be the hardest hit, with an 80 percent increase in flooding, while the United States could become particularly vulnerable because of its unbalanced trade with China.

Adapting to a more flood-prone world

in a study Published this week, Kai Kornhuber and colleagues Mona Hemmati from the Lamont-Doherty Earth Observatory and Andrew Cruzkiewicz The International Institute for Climate and Society from the Columbia Climate Institute details the various ways cities are adapting to extreme rainfall.

While climate change is causing greater downpours, rapid urban development has further exacerbated flooding by covering surfaces that would otherwise absorb rainwater. To counteract this effect, the researchers noted that stormwater management systems and green and blue infrastructure have been shown to help control runoff. Meanwhile, zoning, land-use regulation and buyout programs can help keep people out of flood-prone areas, perhaps making way for parks and green spaces that can soak up water.

Impact-based forecasting and early warning systems could also help reduce losses and deaths from flooding in urban communities, the scientists noted.

They stress that social justice must be at the heart of designing and implementing adaptation measures to extreme rainfall.

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