Weather

Clouds are less sensitive to climate than assumed – Is that stable?

news7g12/04/2022

1 3 minutes read

Clouds are less sensitive to climate than assumed – Is that stable?

The aerial campaign solves parts of the cloud puzzle

A peer-reviewed publication

HAMBURG . UNIVERSITY

**IMAGE: NETWORK WIND CLOUDS NEAR BARBADOS: ONE PLACE WAS USED TO DROP HUNDREDS of Atmospheric Experiments FROM 9 SIZE DURABILITY.** see more
CREDIT: MPI-US

In a major field campaign in 2020, Dr Raphaela Vogel is currently working at the Center for Earth Systems Research and Sustainability (CEN) of the University of Hamburg and an international team from Laboratory of Météorologie Dynamique in Paris and Max Planck Institute of Meteorology in Hamburg analyzed observational data they and others collected in cumulus clouds near the Atlantic island of Barbados. Their analysis revealed that the contribution of these clouds to climate warming must be reassessed.

“Trade clouds affect climate systems globally, but the data exhibit different behavior than previously assumed. Therefore, the possibility of extreme warming of the Earth’s temperature is less likely than previously thought,” said Vogel, an atmospheric scientist. “While this aspect is important for more accurately predicting future climate scenarios, it certainly does not mean that we can stop climate protection.”

To date, many climate models have simulated a significant attenuation of trade wind clouds, which means that much of their cooling function will be lost and thus the atmosphere will remain intact. even warmer. New observational data suggest this is unlikely.

What is certain is that, as global warming increases, more water on the ocean’s surface evaporates and the humidity near the bottom of trade wind clouds increases. In contrast, the air masses in the upper part of the clouds are very dry and only slightly more humid. This creates a significant difference in humidity above and below. In the atmosphere, this is dissipated as air masses mix with each other. The previous hypothesis: drier air was transported downward, causing the cloud droplets to evaporate faster and making the clouds more likely to disappear.

Observational data from Barbados now provide the first robust quantification of how pronounced true vertical mixing is and how this affects humidity and overall cloud cover. Thus, this is the first data to shed light on a process necessary for understanding climate change. Bottom line: stronger mixing does not make the layers below drier or cause the clouds to dissolve. Instead, the data show that cloud cover actually increases with increasing vertical blending.

“That’s good news, because that means trade wind clouds are less sensitive to global warming than long assumed,” Vogel said. “With our new observations and findings, we can now directly test how realistic climate models describe the appearance of trade wind clouds. In this regard, a new generation of high-resolution climate models that can simulate the dynamics of clouds around the globe at the scale of one kilometer is particularly promising. Thanks to them, future predictions will be more accurate and reliable.”

EUREC month-long field campaign⁴A (2020) was designed by team members around extended flights with two research aircraft, equipped with different instruments and operated at different altitudes, and onboard measurements from R/V Meteor — A German research vessel managed by the University of Hamburg. An aircraft was used to drop hundreds of atmospheric probes from an altitude of 9 km. As they descend, the probes collect atmospheric data on temperature, humidity, pressure and wind. The other plane surveyed the clouds at their base, at an altitude of 800 meters, while the ship made measurements on the surface. The result: an unprecedented database that will help understand the ambiguous role of clouds in the climate system – and more accurately predict their role in future climate change.

Whether clouds have a cooling or warming effect depends on their altitude. With a maximum elevation of two to three kilometers, the trade clouds surveyed here are relatively low, reflecting sunlight and cooling the atmosphere in the process. Conversely, higher clouds will amplify the greenhouse effect, causing the climate to warm.

Publication: Vogel R, Albright AL, Vial J, George G, Stevens B, Bony S (2022): Strong Cloud Circulation Coupling Explains Weak Trade Cumulative Feedback; NatureDOI: 10.1038/s41586-022-05364-y https://www.nature.com/articles/s41586-022-05364-y

Nature research summary: https://doi.org/10.1038/d41586-022-03640-5