China Covid shutdown causes record floods – Frustrated by that?

Guest essay by Eric Worrall

Climate mitigation causes more rain? According to scientists analyzing the floods in China in 2020, the reduction in greenhouse gas emissions and coal smoke aerosols during the Covid shutdown in 2020 has resulted in increased rainfall.

Climate change: Covid shutdown linked to record rainfall in China

By Matt McGrath
Environmental reporter

Scientists say that the rapid drop in emissions caused by Covid played a key role in the record rainfall in China in 2020.

Depletion of greenhouse gases and small particles called aerosols have caused atmospheric changes that intensify downpours.

Hundreds of people died and millions more were displaced during a summer of record rainfall.

But long-term emissions cuts are unlikely to trigger similar events.

Many regions of eastern China experienced severe flooding in June and July by 2020. The reduction in emissions contributed about a third of extreme summer rainfall, the researchers said.

…

Several scientific studies have looked at what causes floods, some only to extreme conditions in the Indian Ocean.

Now, an international research team has come up with a new theory. They attribute the sudden drop in greenhouse gas and aerosol emissions, caused by shutdowns during the Covid-19 pandemic, as the main cause of the downpours.

…

Professor Yang Yang from Nanjing University of Information Sciences explains: “There is warming over land due to aerosol reduction but also cooling over ocean due to reduction of greenhouse gases, which increases the temperature difference on land/sea in summer”. Technology, in China.

“This in turn, increases sea level pressure over the South China/Philippines waters and intensifies winds that bring moist air to eastern China, followed by intense rainfall.”

…

Read more: https://www.bbc.com/news/science-enosystem-60423329

Summary of the study;

Published: February 18, 2022

Sudden reduction in emissions during COVID-19 contributes to record summer rainfall in China

Yang yang, Lili Ren, Mingxuan Wu, Hailong Wang, Song Fengfei, L. Ruby Leung, Xin Hao, Jiandong Li, Lei Chen, Huimin Li, Liangying Zeng, Yang Zhou, Pinya Wang, Hong Liao, Jing Wang & Zhen-Qiang Zhou

abstract

Record rainfall and severe flooding hit eastern China in summer 2020. Extreme summer rainfall occurred during the COVID-19 pandemic, which began in China in early 2020 and spread rapidly across the world. bridge. By disrupting human activities, the dramatic reduction in anthropogenic greenhouse gas and aerosol emissions could have affected rainfall in the region in several ways. Here, we investigate such associations and show that the abrupt reduction in emissions during the pandemic underpinned the summer atmospheric convection over eastern China, leading to pressure anomalies. sea ​​level in the northwest Pacific Ocean. Thereafter, moisture convergence intensified to eastern China, and precipitation intensified further in that area. Modeling experiments showed that the reduction of aerosols had a stronger impact on precipitation than the reduction of greenhouse gases did. We conclude that through the abrupt reduction in emissions, the COVID-19 pandemic has made a significant contribution to the extreme summer 2020 rainfall in eastern China.

Read more: https://www.nature.com/articles/s41467-022-28537-9

Reading the research, what they are saying is that the Covid shutdown has reduced coal smoke aerosols, thus making the land hotter than usual, causing a strong wind that sucks in humid air from the sea. Increased rainfall washed more aerosols out into the air, triggering a positive feedback loop that led to widespread flooding.

They also claim the reduction in greenhouse gas emissions has helped strengthen weather patterns, which, by reducing ocean heating, lead to a larger temperature difference between land and sea.

Will long-term reductions in emissions and aerosols lead to increased flood risk in the long term?

… “That’s a good question,” said Professor Yang.

“Because emissions fell dramatically in early 2020 when the Covid-19 pandemic hit, it caused immediate and abrupt changes in different components of the climate system.”

“Such abrupt shifts in the climate system would be very different from those in response to continued but gradual policy-driven emissions cuts.” …

Read more: https://www.bbc.com/news/science-enosystem-60423329

That’s an interesting theory. Living in the subtropical ocean by the sea, I frequently see shore winds, perhaps triggered by heating over land versus sea, which seem to lead to the formation of towering thunderheads near the shore sea.

The authors advise themselves to be cautious, this study is heavily modeled.

But the study is interesting in that it goes against the flow of most claims, that climate change causes more rain. In this case, the scientists argue that climate mitigation, both through Xi Jinping’s efforts to reduce air pollution and the 2020 Covid shutdown, caused the deadly floods – even though they be more cautious in predicting the outcome of long-term, gradual mitigation.