Dec 1 2022Reviewed by Alex Smith
A cooling effect has been produced from cumulus clouds in trade-wind regions that cover around 20% of the planet.
Until now, it was believed that global warming would help decrease the surface covered by such clouds, thereby amplifying the warming. However, Dr. Raphaela Vogel from Universität Hamburg had the potential to disprove that assumption. Their study has just been published in Nature.
In a significant field campaign in 2020, Dr. Raphaela Vogel who is currently at Universität Hamburg’s Center for Earth System Research and Sustainability (CEN), and an international team from the Laboratoire de Météorologie Dynamique in Paris and the Max Planck Institute for Meteorology in Hamburg, examined observational data in fields of cumulus clouds next to the Atlantic island of Barbados.
Their study disclosed that the contribution of these clouds to climate warming has to be evaluated again.
Trade-wind clouds influence the climate system around the globe, but the data demonstrate behavior differently than previously assumed. Consequently, an extreme rise in Earth’s temperatures is less likely than previously thought.
Dr. Raphaela Vogel, Atmospheric Scientist, University of Hamburg
Vogel added, “Though this aspect is very important for more accurately projecting future climate scenarios, it definitely doesn’t mean we can back off on climate protection.”
Until now, several climate models have simulated a significant decrease in trade-wind clouds, which would imply much of their cooling function would be lost, and the air would therefore warm even more. The new observational data displays that this is not possible to happen.
What is doubtful is that, as global warming advances, more water on the ocean's surface tends to evaporate, and the moisture next to the base of trade-wind clouds increases. On the other hand, the air masses in the clouds’ upper part are very dry and only turn out to be moderately moister.
This produces a significant change in moisture above and below. In the air, this is dismissed when the air masses mix. The early hypothesis: drier air has been ecstatic in the downward direction. Also, it results in the cloud droplets evaporating more quickly and thereby making it highly possible that the clouds will mostly disperse.
The observational data gathered from Barbados currently provides the first strong quantification as to how marked the vertical mixing actually is and how this impacts moisture and cloud cover completely.
Intrinsically, it is known to be the first data to offer new insights into a process that is necessary to comprehend climate change. In short: highly intensive mixing does not dry the lower layers or either make the clouds dissipate. Instead, the data displays that the cloud cover actually increases with high vertical mixing.
That’s good news, because it means that trade-wind clouds are far less sensitive to global warming than has long been assumed. With our new observations and findings, we can now directly test how realistically climate models portray the occurrence of trade-wind clouds.
Dr Raphaela Vogel, Atmospheric Scientist, University of Hamburg
Vogel added, “In this regard, a new generation of high-resolution climate models that can simulate the dynamics of clouds around the globe down to scales of one kilometer are particularly promising. Thanks to them, future projections will be more accurate and reliable.”
Vogel, R., et al. (2022) Strong cloud–circulation coupling explains weak trade cumulus feedback. Nature. doi.org/10.1038/s41586-022-05364-y.