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What’s causing the devastating floods in China, India, and Bangladesh?

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Relief teams provide relief in Chennai, India, during floods in November 2021. Credit: Indian Navy

Tens of thousands of people have been forced to flee their homes in central and southern China as a result of flooding from extreme rainfall. the guard reports that about a million people have seen their homes damaged and their lives uprooted by the worst flooding in decades.

In the meantime, CNN reports that heavy rains in India and Bangladesh have caused flooding and landslides that have devastated communities and killed more than 100 people. Flooding in northeastern Bangladesh has left 4 million people stranded, including 1.6 million children UNICEF

State of the Planet gathered comments from several experts at Columbia University’s Climate School to learn more about the meteorological conditions behind these tragic disasters, how climate change is contributing to heavier downpours, and how societies can adapt to an increasingly flooded environment. world.

Flood Factors

Mingfang Ting, a research professor at Columbia Climate School’s Lamont-Doherty Earth Observatory, studies extreme precipitation. She pointed to several large-scale climatic conditions that could contribute to the intense rainfall in China and South Asia:

“I haven’t had a chance to look at the meteorological conditions leading up to the downpour, but as we’re in the middle of the monsoon season there, a lot of rain is expected at this time of year. The question is, why in so High intensity? La Niña is definitely a culprit here. During La Niña, the ocean is warmer in the western tropical Pacific, or warm pool area, allowing more abundant warm, moist air to be transported to southern China when the weather system is aligned. Another potential contributor is the Indian Ocean dipole, which is currently in a slightly negative phase, making the western tropical Pacific also warmer than normal.

“The same concept applies to Bangladesh and Northeast India, where flooding is also occurring this year. However, the negative phase of the Indian Ocean dipole suppresses monsoon rains in central India, although La Niña increases Indian monsoon rainfall, similar to the monsoons in China and Bangladesh.”

In addition to these natural climate modes, Ting suggested that the recent improvements in air quality in China could also contribute to the heavy rainfall, due to a reduction in aerosol particles. Although these particles are harmful to human health,

“Aerosols work to reduce rainfall and cause clouds to stay in the atmosphere instead of settling down, so clearing the air will have the opposite effect, increasing the intensity of rainfall. In terms of human factors versus of the rainfall intensity in recent years, the rather successful improvements in air quality may have made flooding more severe in unexpected ways.”

Contributions of climate change?

Kai Kornhuber, who studies extreme weather at Lamont-Doherty Earth Observatory, said the extreme rainfall and flooding is consistent with what scientists expect to see, and already observe, in a climate-changed world:

While the exact meteorological conditions of this particular event require further investigation, the first-order physical relationship between a warmer planet and more extreme rainfall is well known: Since warmer air can hold more moisture, more extreme rainfall is to be expected.

“The current floods are another sad example of a series of record-breaking extreme precipitation events, such as the floods in Central Europe and the floods in Hunan last year. My colleagues and I describe these events in our recent article in Nature Urban Sustainability and in a comment capable of the planet.”

Coincident concerns

Kornhuber added that it’s particularly troubling that extreme weather events like this are increasingly occurring close together in space and time:

“The parts of the areas affected by the current floods have already witnessed severe flooding in 2021, happening almost simultaneously with the floods in Bangladesh and India and extreme and record-breaking heat in North America, Western Europe, the Central East and East Asia Consecutive and simultaneous extremes could delay and hinder recovery, impacting supply chains and food security, and exacerbating these effects with other unresolved crises, such as the Russian war of aggression in Ukraine and the COVID pandemic.”

Along the same lines, Ting added that southern China has been dealing with drought in recent years, complicating matters:

“This type of extreme swing will make the flooding more dangerous because it can more easily lead to landslides. Any adaptation or solution should be able to deal with more extreme swings like we see now, which may not have been in their planning before.”

Economic and Supply Chain Considerations

In 2018, Anders Levermann of the Potsdam Institute for Climate Impact Research and Lamont-Doherty Earth Observatory co-author of a study who found that climate-related flooding not only affects people’s lives, but also harms economies on a global scale. Due to supply shortages, changes in demand and associated price signals, economic losses can be carried downstream along the global trade and supply network, affecting other economies on a global scale

The study predicted that China would be hit hardest, with an 80 percent increase in flooding, and that the United States, in turn, could be particularly vulnerable due to its unbalanced trade with China.

Adapting to a more flood-prone world

In a study Kai Kornhuber and colleagues Mona Hemmati of the Lamont-Doherty Earth Observatory and Andrew Kruczkiewicz of the International Research Institute for Climate and Society at the Columbia Climate School describe several ways cities can adapt to extreme rainfall.

As climate change causes more intense downpours, rapid urban growth is exacerbating flooding by covering areas that could otherwise absorb rainwater. To counter this effect, the researchers point out that stormwater management systems and green and blue infrastructure have proven helpful in controlling 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 absorb water.

Impact-based forecasting and early warning systems may also help reduce losses and fatalities from flooding in urban communities, the scientists note.

They stressed that social justice should be at the heart of designing and executing adaptations to extreme rainfall.

Climate change factor in ‘unprecedented’ floods in South Asia

Provided by Earth Institute at Columbia University

This story has been republished courtesy of Earth Institute, Columbia University http://blogs.ei.columbia.edu

Quote: What is causing the devastating floods in China, India and Bangladesh? (2022, June 23) Retrieved on June 23, 2022 from https://phys.org/news/2022-06-devastating-china-india-bangladesh.html

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