Paris: People have always studied the skies to predict the weather, but recently scientists have noticed that clouds are changing on a global scale—posing one of the greatest challenges to understanding our warming world.
Some clouds are rising higher into the atmosphere, where they trap more heat. Others are reflecting less sunlight, or shrinking and allowing more solar energy to reach Earth's surface.
Scientists know this is affecting the climate, because the vital role that clouds play in warming and cooling the planet is well understood.
Recent research has shown that clouds—or rather, a lack of them—helped drive a stunning surge in record-breaking global heat over the last two years.
What is less certain is how clouds might evolve as the world warms. Will they have a dampening effect on global warming, or amplify it? And if so, by how much? "That's why clouds are the greatest challenge. Figuring them out is -- and has been -- the big roadblock," said Bjorn Stevens from the Max Planck Institute for Meteorology in Germany, who has written extensively on the subject.
Cloud behaviour is notoriously complex to predict and remains a great unknown for scientists trying to accurately forecast future levels of climate change.
Changes in clouds could mean that, even with the same amount of heat-trapping greenhouse gas emissions, "we could get much more warming or much less warming", said Robin Hogan, principal scientist at the European Centre for Medium-Range Weather Forecasts.
"That's a big scientific uncertainty," he said.
With satellites and supercomputers, scientists are improving cloud modelling and slowly filling in the missing pieces of the puzzle.
Part of the difficulty is that clouds are not uniform—they act differently depending on their type, structure and altitude.
Fluffy, low-hanging clouds generally have a cooling influence. They are big and bright, blocking and bouncing back incoming sunlight.
Higher, streaky ones have a warming effect, letting sunlight trickle through and absorbing heat reflected back from Earth.
In recent decades, scientists have observed a growing imbalance between the amount of energy arriving, rather than leaving Earth, hinting at cloud changes.
As the climate has warmed, certain clouds have drifted higher into the atmosphere where they have a stronger greenhouse effect, said Hogan.
"That actually amplifies the warming," he said.
This is growing evidence that lower clouds are also changing, with recent studies pointing to a marked decline of this cooling layer.
Less reflective cloud exposes more of Earth's surface to sunlight and boosts warming in a "vicious feedback cycle", said climate scientist Richard Allan from the University of Reading. — AFP
Oman Observer is now on the WhatsApp channel. Click here
