Circumstantial evidence indicates climate change as worsening the deadly deluge that just flooded Dubai and other parts of the Persian Gulf, but scientists have not discovered the definitive fingerprints of the greenhouse gas-triggered warming they observed during other extreme weather events, according to a new report.
Between 10 and 40 percent more rain fell in a single day last week, killing at least two dozen people in the region. United Arab Emirates, Oman and parts of Saudi Arabia — what it would have been like in a world without the 1.2 degrees Celsius (2.2 degrees Fahrenheit) warming caused by the burning of coal, oil and natural gas since the mid-19th century, scientists say of World weather attribution said Thursday in a flash study too recent to be peer-reviewed.
In at least one location, a record 11 inches of rain fell in just 24 hours, more than twice the annual average, crippling the usually bustling city of skyscrapers into a desert.
One of the key tools of the WWA’s more than 60 previous reports has been the creation of computer simulations comparing a real weather event to a fictional world without climate change, but in the case of Dubai there was not enough data so that these simulations can perform such a calculation. . But analysis of decades of past observations, the other main tool they use, showed a 10 to 40 percent increase in precipitation amounts.
Even without computer simulations, the clues continued to point toward climate change, scientists say.
“It’s not as clear a fingerprint, but we have a lot of other circumstantial evidence, other lines of evidence that tell us that we’re seeing this increase,” said Friederike Otto, a climate scientist at Imperial College in London, who coordinates the attribution study team. “This is what we expect from physics. This is what we expect from other studies that have been done in the region, other studies around the world, and there is nothing else that could explain this increase.
There is a long-known effect in physics which reveals that the air retains 7% more humidity for every degree Celsius (4% for every degree Fahrenheit).
Otto said she was confident in the finding, but said it was one of the most difficult attribution studies the team has undertaken.
El Niño, which is an occasional natural warming of the central Pacific that changes weather systems around the world, was a significant factor, according to the report. These heavy showers in the Gulf have occurred in the past, but only during an El Niño event. And researchers said these past deluges appear to be trending toward intensification — something scientists have long predicted would happen in many parts of the world as the planet warms.
These floods, caused by two distinct and almost simultaneous storm systems, would not have happened without El Nino, said Mansour Almazroui, co-author of the study from the Center of Excellence for Climate Change Research (CECCR). , from King Abdulaziz University in Saudi Arabia. This also would not have been the case without human-caused climate change, Otto added.
Because rainfall amounts varied by region and due to lack of data, the report could not determine whether climate change had increased the likelihood of such downpours in Dubai, but Otto estimated that it is probably around three times more likely now. than in pre-industrial times.
The report and its authors have thrown cold water on speculation that cloud seeding in the United Arab Emirates had nothing to do with the amount of rain or its likelihood. Many scientists dispute the general effectiveness of cloud seeding. Despite this, the storm system’s clouds were not seeded, the report said. And the results of cloud seeding, if any, are generally more immediate, Otto said. And this storm was predicted days in advance.
“This type of precipitation never comes from cloud seeding,” Almazroui said at a news conference Thursday.
Although the authors use well-established techniques and this is what scientists expect when it comes to climate change, when there is a disagreement between computer simulations and observations, conclusions should not be drawn , said Andrew Weaver, a climatologist at the University of Victoria, Canada. This is not part of the research.
There is a strong enough case that greenhouse gas emissions are a factor, several other outside scientists said.
Malte Meinshausen, a climate scientist at the University of Melbourne, Australia, called Thursday’s study a “well-balanced, incredibly detailed and suitably conservative assessment.”
“This work, combined with theoretical and attribution studies associated with other increasingly frequent extreme rainfall and flooding events around the world, convincingly demonstrates that global warming has amplified recent rainfall events and extreme flooding in the United Arab Emirates and Oman,” said climatologist Jonathan. Overpeck, dean of the environmental school at the University of Michigan. “This is what global warming increasingly looks like: more severe climate extremes and even more severe human suffering. »
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