July 3, 2013. According to experts, this year should not have expected the frequent occurrence of night-shining clouds. However, this "ripple" in the atmosphere and space, also known as noctilucent clouds or polar mesospheric clouds, there is more and more intense than expected.
Says lead study author physicist David Siskind, "The number of observed brilliant clouds directly opposite to our expectations."
See also: In the Northern Hemisphere, the season of noctilucent clouds
The fact that the experts were not able to take into considerations the brilliant clouds a number of anthropogenic factors, often becoming the cause of their appearance. It turns out that this is a rare phenomenon generated not only by natural factors but also, for example, launches rockets into space, as well as increases in greenhouse gases.
NASA conduct systematic observations of bright clouds in 2007. Agency experts have argued that without the missile launches and increasing concentrations of greenhouse gases in the atmosphere, this phenomenon would be observed less frequently.