BRT posted a blurb titled Albedo, showing the enormous difference of ice vs water in terms of the fraction of solar energy (shortwave radiation) reflected from the Earth back into space. It is a measure of the reflectivity of the earth's surface. Ice, especially with snow on top of it, has a high albedo: most sunlight hitting the surface bounces back towards space. something hauntingly depicted in NASA's nighttime shot of noctilucent clouds surrounding the North Pole on June 10, 2015.
Noctilucent clouds were first described in the mid-19th century after the eruption of the Krakatau volcano. Volcanic ash spread through the atmosphere, making for vivid sunsets around the world and provoking the first known observations of NLCs. At first people thought they were a side-effect of the volcano, but long after Krakatau’s ash settled, the wispy, glowing clouds remained.
In the past decade, AIM has been observing and measuring these seasonal, high-altitude cloud formations. Researchers have found that they are appearing earlier and stretching to lower latitudes with greater frequency. There is some evidence that this is a result of increased greenhouse gases in the atmosphere.
Though they were not thick enough to appear in AIM imagery, some noctilucent clouds were visible to ground-based observers in the continental United States on June 9 and 10.
Here's what they look like from the ground.
Interesting, don't you think?