Once rare, but now becoming increasingly common, noctilucent, or “night-shining”, clouds form in the upper part of Earth’s atmosphere, tens of kilometers above weather clouds, at mid-latitude locations.
As the lower atmosphere warms during the summer months, air is circulated upwards where it expands and cools in the Mesosphere, around 80 kilometers (50 miles) above sea level. If there is enough water vapor in these cold conditions, it will freeze around specks of meteoritic dust, producing wispy, swirling clouds. Although too thin to be seen during daylight, as the Sun dips below the horizon its light continues to be reflected by the high-altitude clouds, illuminating the phenomena against the dark sky.
In late June, astrophotographer Ollie Taylor captured the summer phenomenon sweep over a 12th-century church in Dorset, on the south coast of the UK, between 2am and 2.50 am local time, pictured above. “It was an excellent night of shooting, arriving at location in the evening already greeted by noctilucent clouds better than I had previously seen in the south of England,” Taylor said in a statement. “The electric blue complemented the misty landscape and eerie structure.”
Night shining clouds were first observed by humans in 1885, two years after the Krakatoa volcano in Indonesia spewed huge amounts of water vapor up into the atmosphere (a key ingredient needed in the cloud’s formation). For the following years the clouds were only spotted from one particular location every few decades, but they soon became a more regular feature of summer nights.
A 2018 study, published by the American Geophysical Union, concluded that the increased visibility of noctilucent clouds was down to humanity's impact on the climate. The extraction and burning of fossil fuels has released greenhouse gases into the atmosphere, including methane, which at high altitudes produces water vapor. Since 1871, the report found that there had been a 40 percent increase in water vapor 80 kilometers (50 miles) high at mid-northern latitude, meaning that there is now a good chance of seeing the clouds several times each summer.
From the ground to space, humans have captured the night-shining wonder in some truly breath-taking images. Even astronauts have seen the feathery patches during their stay on the International Space Station.
Because the conditions for noctilucent cloud formation are so specific they are hard to predict more than a few hours in advance, but keen watchers try to share any tip-offs across the web. If you can’t see them in person, thankfully the images alone are enough to soothe the soul.
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