Today’s post is part of a special series here on Planet Pailly called Sciency Words. Every Friday, we take a look at a new and interesting scientific term to help us all expand our scientific vocabularies together. Today’s word is:
On Thursday, we talked about what it would take to terraform Venus. Turning Venus into another Earth is, in short, difficult. So instead, how about we turn Earth into another Venus?
In the worst-case scenario for climate change, accumulating greenhouse gases in Earth’s atmosphere trigger a runaway greenhouse effect analogous to what happened long ago on Venus. Hence the name “Venus syndrome.”
Here’s how Venus became the charming hellhole we know today:
- Venus had oceans: Early Venus probably had oceans of liquid water. As the early Sun grew brighter, these oceans warmed up, releasing water vapor. Water vapor, believe it or not, is a greenhouse gas. It’s transparent, so light energy passes straight through; but it traps heat, so once light energy becomes heat energy, it can’t escape.
- The oceans boiled: The initial temperature change would have been relatively minor, but it created a positive feedback loop. More water vapor trapped more heat, which evaporated more water, which trapped more heat, until the oceans boiled away completely. Then things got worse.
- The rocks sublimated: The temperature rose to the point that certain carbon-containing rocks sublimated (turned from solids directly into gases). Carbon dioxide took over for water vapor as Venus’s principle greenhouse gas. More CO2 caused more rocks to sublimate, generating more CO2, and… well, you get the idea.
- The sulfur cycle began: The now ludicrous temperatures also released sulfur compounds into the planet’s atmosphere, providing the key ingredient for Venus’s infamous sulfuric acid clouds.
So could this happen on Earth? Could manmade greenhouse gases initiate a runaway greenhouse effect, ultimately boiling our oceans and sublimating the carbon and sulfur in Earth’s crust?
According to the U.N.’s International Panel on Climate Change, human activities have “virtually no chance” of causing Venus syndrome. They’re predicting less dramatic consequences: rising sea levels, mass extinctions, etc. So that’s reassuring, I guess.
The problem is we don’t know the point at which slight changes to Venus’s environment began spiraling out of control. This makes Venus the subject of rather urgent research by both climatologists and planetary scientists.
Venus syndrome is a worst-case scenario, meaning it’s the greatest extreme on a spectrum of possibilities. But that doesn’t mean we can ignore it. The story of humanity’s exodus from a Venus-like Earth needs to be told, perhaps as science fiction, before it has the chance to become science fact.
2009 Assessment Report from the International Panel on Climate Change.
Venus and Mars Hold Priceless Climate-Change Warnings for Earth from The Daily Galaxy.
Could Greenhouse Gases Turn Earth into Venus? (Yes, But Not Anytime Soon) from Mother Jones.
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