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The highest clouds in the Earth's atmosphere have generally been a rare and beautiful sight but scientists say that they are now becoming more visible because of human activities.
A new study found noctilucent clouds – the silvery blue (and sometimes reddish – orange) clouds that shine in the sky – we can see it more frequently because of the increase in the water vapor in the atmosphere.
Researchers say this phenomenon is "an indicator of climate change of human origin".
Noctilucent clouds form when water vapor freezes around tiny dust particles from meteors in the mid-atmosphere (mesosphere) – about 50 miles above the surface of the Earth [19659002] of water vapor to accumulate in the air.
Observations becoming more frequent in the twentieth century, scientists began to wonder whether climate change was making noctilucent clouds more visible.
In the new study, researchers from the Institute of Atmospheric Physics of Kuhlungsborn, Germany, used satellite observations and computer models to simulate the effects of greenhouse gases on cloud formation Over the past 150 years
Simulation results indicate that methane emissions have increased water vapor concentrations in the mesosphere by about 40% since the late 1800s, which in turn more than doubled the amount of ice that forms in the mesosphere
The researchers say that is because the water vapor in the mesosphere comes from two sources: the vapor water from the surface of the Earth that is transported up, and methan e, a gas that produces water vapor by chemical reactions in the average atmosphere.
They conclude that human activities are the main reason why noctilucent clouds are significantly more visible than it was 150 years ago
Franz-Josef Lubken, an atmospheric scientist at The Institute of Atmospheric Physics of Leibniz and lead author of the study, said: "We speculate that clouds have always been there, but the chance of seeing one was very, very poor in historical times. " usually visible at dawn and dusk, when the sun illuminates them under the horizon.
Simulations have revealed the presence of noctilucent clouds depending on the mesosphere conditions as well as the solar cycle (the phases in the sun's magnetic field that lasts about 11 years) and can fluctuate from year to year .
But over the entire period studied, the clouds became much more visible.
According to Professor Lubken, people living in mid-high latitudes now have a good chance of seeing noctilucent clouds. Several times each summer.
These clouds would probably have been visible only once every few decades in the 19th century, he added.
The study is published in Geophysical Research Letters.
– Press Association
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