Think of it as extreme global warming.
Using a computer model, researchers examined what might happen if the amount of carbon dioxide in Earth’s atmosphere increased dramatically. Really, really dramatically. In a paper published today in Nature Communications, NOAA researcher Max Popp took a look at what would happen to a watery planet like Earth if carbon dioxide levels in the atmosphere just kept going up.
Right now, the amount of carbon dioxide in our environment is hovering at 400 parts per million a number that is already large enough to start affecting our environment. Carbon dioxide is a greenhouse gas, meaning that it traps heat within the Earth’s atmosphere. That’s why governments around the world are trying to reduce the amount of carbon dioxide put into the atmosphere annually, in the hopes that the planet won’t get so warm that parts of the planet become uninhabitable. But what if those reductions don’t happen, and instead, everything goes horribly wrong?
Looking at a computer model of a world completely covered in water (a simple analog of the Earth, which is 71 percent covered by water) Popp and colleagues looked at what would happen if the carbon dioxide levels rose to staggering levels. They found that when the level of carbon dioxide in the atmosphere reached 1,520 parts per million, temperatures at the surface of the world would reach nearly 135 degrees fahrenheit, evaporating vast amounts of water into the atmosphere, and sending them high up into the atmosphere, near space. In this scenario, called the “moist greenhouse” in the paper, Popp estimates that water could easily escape from the water world’s atmosphere into space. Worse, they found that once moist greenhouse conditions were reached, thy couldn’t be reversed, even by removing the excess carbon dioxide.
A similar situation could happen in a few billion years as the sun brightens in the natural course of its evolution, sending out so much more heat and light that the temperature of the Earth’s surface rises, creating a similar moist greenhouse effect.
But there’s no need to worry right now about whether the world will end in fire or gas. Given the lengthy time scale to reach either situation (millions if not billions of years), these are more geological doomsday scenarios than human ones. Isn’t that comforting?