LONDON: Pakistanis are calculating the damage from the country’s worst recorded floods, but heavy rains hit southwest China last month as the Texas city of Dallas recovered from a 10-inch deluge in a day. ing.
Both of these rainfall disasters followed heat waves, suggesting that the region is swinging wildly between two opposing extremes. But extreme heat and extreme rainfall go hand in hand, and climate change is fueling gas, scientists say.
South Asia’s sweltering spring temperatures above 50 degrees Celsius have likely warmed the Indian Ocean. It would have rained more than three times the average and flooded a third of the country. .
More than 1,100 people have died, crops have been ruined and homes destroyed, prompting urgent calls for help.
It will take weeks, if not months, to determine exactly what role climate change may have played in this year’s floods, but scientists say it’s extremely overheating. Heat waves are already becoming more frequent and intense around the world, with increased evaporation from both land and sea. A warmer atmosphere can also hold more moisture, so water vapor builds up until the clouds finally break and bring more heavy rain.
“In hotter climates, we would expect the same place to experience both flooding and drought,” said Deepti Singh, a climate scientist at Washington State University.
The Dallas area has been completely dry for three months, with extreme drought affecting more than half of Texas. Cotton withered in the fields. Ranchers were forced to kill many cattle due to lack of fodder. Hardened and cracked soil forms a dry checkerboard pattern across the landscape. This is the perfect environment for flash floods.
It finally rained on August 21, reducing the water by nearly 10 inches (about 10 inches) within 24 hours, but the ground was too hard to absorb the deluge and much of the water spilled into the city. flowed out to Interstate traffic has stopped. Flight canceled. Also, apartments in the historic district of Old East Dallas were flooded.
In drought-stricken areas, “the ground can behave like concrete in an urban environment,” said Liz Stephens, a climate scientist at the University of Reading, UK.
Unlike floods caused by the gradual inundation of rivers, flash floods are caused by short periods of heavy rain (usually less than six hours) that provide little warning before the water swells into a torrent. In the center of urban populations they pose the greatest danger. But flash floods often tear through the desert canyons of Utah and Arizona, threatening hikers.
Since July, the United States has experienced four major flash floods in Kentucky, Eastern Illinois, Death Valley in California and St. Louis in Missouri. Each saw enough rain to be considered a once-in-a-thousand-year event, according to historical trends.
It is unclear how much that frequency will increase as the world continues to warm.
Flood here, flood there
China’s drought-stricken Yangtze River Basin, which was hit by the worst heat wave in 60 years during the summer, is suffering from shortages of both electricity and water. Some states within the basin, desperate for rain, began to “seed” the clouds, sending planes into the sky to release the chemical silver iodide and break the clouds.
But with late summer rains, officials are worried about too much water. More than 119,000 people have fled flood-prone areas in southwestern China, according to state media.
The Ministry of Emergency Management warned on Monday that parts of China were “alternating between droughts and floods” and urged vigilance to monitor dry riverbeds that have been flooded by heavy rains this week. The ministry has also asked local governments to harvest rainwater as it could help relieve other drought-hit areas in the country.
Weather phenomena across the northern hemisphere can also be related by the polar jet stream, a fast-moving air current that moves the weather system from one part of the world to another.
However, scientists have found that recent warming trends associated with air circulation disturbances may also increase the likelihood of extreme events occurring at the same time.
Jet stream disturbances are still an intensely researched topic. However, one recent study suggests that these factors combine to make simultaneous heat waves seven times more likely in the northern hemisphere than they were 40 years ago.
“Warming trends are a major factor behind the increase in concurrent heat waves,” says Kai Korn, a climate scientist at Columbia University in New York who was part of the team that worked on the study, including Singh. Hoover said.
However, there is evidence “to believe that atmospheric dynamics contributes to this increasing trend,” including studies of jet streams.