What was claimed
Unusual cloud formations captured in a picture are “not natural” and the result of chemtrails.
Our verdict
Though relatively rare, so-called mackerel sky cloud formations are natural.
Picture does not show ‘unnatural’ cloud formations
2 August 2022
A post on the public Facebook group Chemtrails UK claims to show a picture of a sky that is “not natural”. It actually shows a picture of a well-known and completely natural cloud formation.
The image accompanying the post shows a street scene below a sky completely filled with long, undulating but evenly spaced strips of cloud. A caption attached to the post says: “This makes me so sad how can people not see this is not natural.”
The group where the image has been posted is linked to the chemtrails conspiracy theory, a subject we have covered before. The word chemtrail is used to misleadingly describe the white lines that appear in the sky behind planes, which proponents of the theory claim are being deliberately released and contain chemicals which either poison the population or control the weather. The post implies that the clouds in the picture are the result of such activity.
In reality, the white lines that sometimes appear behind aircraft are contrails and are formed when the warm moist exhaust fumes from jet engines mix with the cold air, producing ice crystal clouds.
The image shared in the Facebook post shows a natural formation sometimes known as “mackerel sky” because the waves of altocumulus or cirrocumulus clouds that form them resemble the scales of the fish.
According to the Met Office, cirrocumulus clouds are made up of both ice and 'supercooled' water that remains a liquid, even at temperatures well below zero degrees celsius. They form when turbulent vertical currents meet the top of the lowest part of the atmosphere [known as the troposphere] creating the puffy shape. They can also form through contrails.
Altocumulus clouds can form through the breakup of other clouds, moist air pockets being cooled by gentle turbulence or atmospheric waves from mountainous terrain. While cirrocumulus clouds are always white and tiny, altocumulus clouds can be white or grey and have shaded sides.
Mackerel sky formations have been frequently reported in both local and national media. The dramatic patterns have been frequently photographed.
This article is part of our work fact checking potentially false pictures, videos and stories on Facebook. You can read more about this—and find out how to report Facebook content—here. For the purposes of that scheme, we’ve rated this claim as false because the photographed cloud formations are natural.