Can Earth have blue skies and diverse clouds yet never a drop of rain?

Question

I'm trying to figure a threshold of environmental conditions where the Earth hits a point of no return on falling rain. The thought seems preposterous to me, but recently I saw some movie that claimed no rain had fallen in a decade but yet the sky in the background was like a normal day on the prairie. Similarly, the land around was alive and well. I found this implausible, but the more I thought about it the more I realized I have no idea what I'm talking about.

I don't know that there isn't some global condition the Earth as we know it could hit where water would evaporate, and form clouds, but never result in rainfall anywhere on the planet (oceans may be excused I suppose if that factors at all). Try as I might, I cannot fathom how such a scenario could work without some kind of radical shift in the global condition itself. But even then, I don't know if it is possible to terminate rain while there are still humans alive to observe it.

At some point the planet would go from having the last bits of rain, to having nothing. And I wonder what that threshold would look like. Be it the wild frontiers as depicted in this film, or something closer to Mordor, under hoof and claw so to say.

Does anyone out there have the scientific prowess to generally lay out the requirements for a whole planet to form clouds and never have those clouds meet the required conditions to rain? Or is that scenario in itself self-defeating?

Answer 1

A bit of background: a pet peeve

One of my bigger peeves with the environmental activist crowd is that they keep focusing on the planet, as if we could kill it. Earth is incredibly resilient and its ability to bring about life equally so.

But that doesn't mean humans would survive.

And that's my peeve. Climate change is certainly happening. Some of it is natural (even cyclical) and some of it is human-contributed... but in the end, there's no point worrying about any permanent change to the environment if there isn't at least one human left to scream "I told you so!" The goal is to save the humans — Mother Earth has survived much worse than anything humans have thrown at her so far or likely ever will.

A Narrow Band of Happiness

Why am I telling you about my peeve? Because the environmental window, what I'm calling the "band of happiness," is really quite narrow. Even on our Goldilocks planet, the temperature can't be too hot or too cold, humidity can't be too high or low, the partial pressure of oxygen can't be too high or too low. And rain is very much a part of that narrow band of happiness.

If the global average temperature is too hot or too cold... it stops raining.

It is rare to get rain when the temperature rises above 100°F (38°C), since heat of that intensity is usually accompanied by a high pressure system with sinking air, which discourages clouds and rainfall. (Source)

This is part of what @AlexP in his comment meant by Virga. Virga is rain that never hits the ground because it's too hot and evaporates. But as the environment gets hotter, even virga stops. The planet gets to a point where (simplistically) water cannot condense into droplets.

To be fair, if your looking for never one drop of rain on Arrakis Earth, then you can't have clouds. That might be a simplification, but the problem is to have clouds you must have humidity. If you have humidity you have the possibility of rain. In Herbert's Dune series, the planet Arrakis is a desert planet. No rain anywhere on the planet. But even it has polar ice caps and water condenses during the night as temperatures drop. So a discussion of "what's rain?" might be in order. But from the perspective of water falling from the sky, it's really hard to have a thriving ecology without either rain or a lot of ground water (and good ground water tends to lead to... yup! Rain!) But enough of that...

Yes. It has to be cold for it to snow, if your definition of cold is like that of most folks who live in the mid-latitudes. But the atmosphere must contain moisture to generate snow--and very cold air contains very little moisture. Once the air temperature at ground level drops below about -10 degrees Fahrenheit (-20 degrees Celsius), snowfall becomes unlikely in most places. Therefore, significant snowfall at such very low temperatures is rare. (Source)

So, on the flip-side of our narrow band of happiness is the reality that snow pretty much stops falling when it gets too cold. (Note the truth that there's always a little bit of snow, just as there's always a little bit of rain. There's too honking much water on Earth to completely stop raining/snowing.)

Is it that simple?

No. In reality you have temperature, pressure, humidity, wind, altitude, and a whole lot of other variables that affect when precipitation can form. If you're looking for a scientific justification for your condition on Earth, you're kinda in the wrong place. We focus on helping people build imaginary worlds, so the focus is the ability to rationalize the result. When possible, to the greatest degree of known scientific plausibility possible. So, we can rationalize the cessation of rain by shifting the global temperature outside the narrow band of happiness.

But...

There is one more thing, and this bounces off the peeve I mentioned at the top of the post. Greenhouse gasses.

Greenhouse gases (GHGs) are a set of gases that accumulate in the lower layer of the atmosphere, the troposphere, and absorb infrared radiation, which contributes to increasing the average temperature of the Earth's surface. (Source)

This is how you could rationalize never one drop of rain upon the Earth... but still have clouds. Greenhouse gasses accumulate in the lower atmosphere, leaving the upper atmosphere (where clouds can still form) cooler, which is needed for cloud formation. The hotter temperatures keep the rain from falling as described above.

But there is that nasty problem of a happy ecology

One of your goals was well expressed as...

Similarly, the land around was alive and well.

Does it matter what you meant by that? The life deep in the Sahara dunes is different from life in the rural areas around Portland, Oregon and different still from life in Antarctica. As you remove rain, the Earth's flora must depend more (much more) on ground water. This means your desert biomes will expand and fill space that once depended nearly exclusively on rainwater.

Does that meet your expectations? It's still viable life. But if your goal is to have Earth as it is right now sans rainfall, that's not going to happen.

And if that program you watched demonstrated happy flora in a region with no rainfall for a decade, it's getting it from nighttime condensation and groundwater — assuming what you were looking at wasn't the result of irrigation.

But, eventually... it'll rain

Science today believes that after the Earth formed and began to cool, there eventually came a time when it began to rain. And rain... and rain... perhaps for millions of years. This makes sense. The world was so hot that the water in the atmosphere couldn't condense and fall to the ground. Then a time comes when it does rain and that rain hits the still-too-warm mantle, where it evaporates and cools into rain. Over and over until the mantle is cool enough to permit standing water.

Remember, Earth is resilient! Life is resilient! Which means it's going to be whomping difficult to create a permanent solution that keeps rain from falling. Because due to nothing more than the Earth's distance from the sun, the Earth will eventually cool enough (the greenhouse gasses reabsorbed into the ground, the temperature warms or cools to the narrow band of happiness, etc.) to allow rain again. Because that's how the Earth works.

Yes, you could move the planet closer to the sun or further away from it (to get it outside the band of happiness). Or you could make the sun hotter or cooler. Both would be permanent changes... but you wouldn't have life on that Earth as you see it today.