I don't normally seek out space news that's this close to home; instead, I tend to lean towards powerful black holes and distant galaxies. But this topic happened to weird me out enough to merit a thorough investigation.
When I first started learning about these guys, they reminded me of the northern lights - a beautiful but elusive atmospheric phenomenon. Then I started getting increasingly creeped out.
It turns out that noctilucent clouds first appeared in 1885; not only is this a very recent phenomenon, but 1885 is two years after the massive eruption of Krakatoa.
Krakatoa is a famous volcanic erupton (in Indonesia) that dumped enough ash into Earth's atmosphere to plunge Europe and North America into a "mini ice-age" of decreased harvests due to lower temperatures. Climate scientists hypothesize that the effects of the ash in the atmosphere or the inception of the industrial revolution led to the first sightings of noctilucent clouds.
So not only are these clouds new to Earth's atmosphere, but they tend to show up following extreme climate catastrophes. Then why are there more and more news reports of sightings of noctilucent clouds? And what do we even know about them?
First off, noctilucent means "night shining" in latin; these clouds primarily occur at extreme latitudes following sunset. If you've ever gone out and looked for satellites around sunset, hunting down these clouds would be very similar. This is because they are extremely high-altitude. In fact, they form in the mesosphere. The mesosphere is the atmospheric layer above the troposphere and, to introduce some context here, it is commonly taught in elementary and middle school science that ALL WEATHER occurs in the troposphere. But noctilucent clouds form as high as 76 km (47 miles), which is five times higher than the highest elevation cirrus clouds in the troposphere.
But the weirdness doesn't stop there. It was previously thought that mesospheric conditions are just too dry and cold to produce the ice crystals necessary to form clouds. And this is where we arrive at the part where noctilucent clouds play the role of the canary in the mine.
Recent observations show that the frequency, brightness, and extent of these clouds are increasing. There are a couple of competing theories for why this is happening (Remember, a theory is defined as a well-tested result in the scientific community).
- Some climate scientists think that global warming is cooling the mesosphere leading to the formation of more clouds. Note that this is an example of how global warming doesn't just warm the Earth - it also produces worldwide climate change that manifests itself in different ways. For instance, some places on Earth may experience colder summers and more rain as a result of global warming, much like the mesosphere experiences cooling.
- A competing theory is that methane is being pushed higher up into the atmosphere than ever before, and chemical reactions with methane are producing more water vapor in the atmosphere.
Whichever theory you choose to believe, these clouds are man-made. The important take-away is that people are inducing global climate change through the production of greenhouse gases. This climate change not only changes the surface of the planet, but it also affects our fragile atmosphere in ways that we have yet to fully understand. Maybe it's time to stop gambling with our atmosphere...