Clouds again: “For 50 years, people have been making climate projections, but all of them have had a false representation of clouds”, says a top atmospheric science professor who served as a lead-author of Chapter 7, “Cloud and Aerosols” for the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.
Despite this glaring deficiency in climate models, governments insist on framing energy policies on the assertion that human ’emissions’ will be the main cause of any observed or future global climate change.
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Above the Atlantic Ocean, puffy white clouds scud across the sky buffeted by invisible trade winds.
They are not ‘particularly big, impressive or extended,” says Dr. Sandrine Bony, a climatologist and research director at the French National Centre for Scientific Research. “But they are the most ubiquitous clouds on Earth.”
Clouds are one of the biggest question marks in global climate models, and a wild card in predicting what will happen to the climate as temperatures rise, says Phys.org.
They play a vital role in how much of the sun’s radiation makes it into and gets trapped in our atmosphere.
The more clouds there are, the more radiation bounces off their tops and is reflected back into space; it also means that if there are more clouds, the radiation reflected by Earth gets trapped.
Historically researchers have struggled to understand cloud properties, how they currently behave, and how they will react to the increased temperatures caused by climate change.
It comes down to an issue of scale, explains Dr. Bony. From the microscopic interactions of atoms to atmospheric currents that act over thousands of kilometres, many forces affect how clouds form, their composition and behaviour.
The clouds resembling cotton wool in the Atlantic, which Dr. Bony and her colleagues study, are a good example. “A little change in their properties has a huge impact on the global radiative balance (the balance between how much of the sun’s energy makes it into Earth’s atmosphere and how much escapes),” she said. Because these fair-weather clouds (known as cumuliform clouds) are so common, a small change carries ‘huge’ statistical weight in the global climate.
“It’s the biggest question—there is no bigger question,” said Professor Bjorn Stevens, a director of the Max Planck Institute for Meteorology in Germany and Dr. Bony’s co-leader on the EUREC4A project which set out to investigate these fluffy white clouds.
“For 50 years, people have been making climate projections, but all of them have had a false representation of clouds.”
These projections, he says, have suffered from an inadequate understanding of the factors determining how cloudy climate will be and have not been properly represented in the models.
The EUREC4A project, which began as a modest field experiment to measure air motion and cloudiness, attracted numerous partners and expanded in scope. In the end, it encompassed five crewed and six remotely piloted research aircraft, four ocean-going research vessels, a flotilla of drifters and gliders, an array of satellites, and measurements from the Barbados Cloud Observatory.
“The experiment grew in complexity and scope to address a number of other fascinating questions,” said Prof. Stevens, such as how much and how easily clouds rain, and how eddies in the ocean and the clouds above affect each other.
The team is currently writing up their results, and hopes that their measurements will provide the answers to these questions.
“We will be setting a ground truth for a new set of climate models,” he said.
Full article here.
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November 10, 2020 at 04:12AM