What’s In A Cloud? More Than You Think
“The amount of microbial life present in the cloud droplets that make up a winter storm is amazing.”
– Gary Franc, microbiologist and plant pathologist at the University of Wyoming, in The Clouds Are Alive by Douglas Fox, Discover, April 2012
Here’s an easy question. At what temperature does water freeze or thaw?
If you answered zero Celsius (32 Fahrenheit) you would be with the majority. If you are savvy enough to know about salt water, such as in oceans, you will know that sea water may remain liquid down to -4C. And salt on icy winter roads will melt down to -4C. That puts you in a minority.
If you answered anywhere between -40 (C or F, they coincide at that temperature) and +10C you would be technically correct–“technically” because even though this is true in nature it’s not a fact you would want to argue in court, or even with your mother. It’s not simple.
Water in the stratosphere has been found still liquid at nearly -40 and ice crystals have been seen forming at +10C in some clouds. No, I am not lying to you. Keep reading so you will learn how these are possible.
First of all, what do you think clouds are made of? Water droplets, yes. (Not steam, which is water as a gas, and that is technically invisible.) Water droplets tend to form around dust particles in the air. Generally speaking, when you get smacked in the face with rain drops each one has at least one particle of dust in it.
Who cares about the dust? Maybe you if you realize that the dust may have travelled the world more than you have. A dust particle in a droplet of water in a cloud in North America could well have come from Africa’s Sahara Desert. Or from China’s Gobi Desert. Or, who knows?
The well read among us will know that “foreign” dust could have brought along with it microbes from its land or origin. These microbes, blown in the wind, hitchhiking on dust, might deliver infectious disease right to your nose without your ever owning a passport.
True, the likelihood of your dying of a disease blown from a different continent than your own, on dust, is small. But microbes in the air are far more prevalent that you may imagine. As our quote at the beginning said, the air is full of microbial life.
Most of it will do you no harm. But so little study has been done on this subject that we have no way to know today what diseases and afflictions we and those we know may get that may have begun thousands of kilometres away from our home. We may accept that SARS and swine flu are delivered peer-to-peer by human travellers, but not that other diseases might be brought to us in the air. From a distant continent.
Kimberley Prather, an atmospheric chemist who heads her own research group at University of California San Diego, is not shy about getting up into the clouds (even rumbling ones) to find out what is going on inside. What she has learned is enough to make your jaw drop.
Think about it: what makes ice form from water, other than the obvious, ambient temperature? Why do some clouds drop rain while others don’t? The answer in both cases is microbes.
Bacteria, algae and fungi get swept up by wind at ground level and make their way into the air as high as jetliners. “There’s a whole ecosystem going on in the clouds that’s largely undefined,” says Gary Franc.
Two million tons of bacteria, 55 million tons of fungal spores and an unguessable (at this time) quantity of algae make their way into the atmosphere each year. Never mind pollution in the air, this is nature in action. A great deal of study will be needed to determine what effects these have on our weather, on next year’s harvest, even on our personal health.
Ice will form by itself from water (so far as we know today), but this happens very slowly (like ice cubes in your fridge freezer). How can this happen so quickly in the atmosphere when ice crystals form and snow falls to the ground?
Professor Prather and others have shown that the bacterium Pseudomonas syringae has a gene in its DNA that prompts ice to form from water droplets. You read that right. At least one variety of bacteria can cause water to freeze into ice by activating a gene in its body.
Why is this important? Ice crystals are heavier than water droplets. Ice falls, delivering water (as it melts) to the land below. If cloud seeding silver iodide were loaded up with P. syringae bacteria when sprayed into clouds, drought-dried land could be persuaded to become fertile again.
That means more food to feed the seven billion (and growing) of us on the planet today.
It also could mean new ways to control the spread of diseases that seem mysterious and stubborn to us now.
Stay tuned, the most populous life form on the planet, bacteria, have much to teach us.
Bill Allin is the author of Turning It Around: Causes and Cures for Today’s Epidemic Social Problems, a guidebook for teachers and parents who want to raise well balanced children who can have good lives, not just good jobs.
Learn more at http://billallin.com