How Does the Earth Lose its Heat Unlike Other Planets?


Ever since the 1950s, scientists have observed something unique about our planet, which is that it loses heat – that is, emits heat into space.  The process could be compared to what happens when we use an oven.  The more the oven heats up, the more heat enters the kitchen.  Of course, when it comes to this process in a planetary context, things are always more complicated – if not, in this case, mysterious – and scientists are still trying to get a firm grasp on why this is something that occurs on Earth, while it doesn’t appear to happen with any other planets.

The Earth’s Heat Loss

It sounds simple enough – the higher the surface temperature of Earth, the more heat is shed into space.  But, despite how simple this relationship is, scientists still don’t quite understand why it happens in the first place, especially considering the fact that it hasn’t been observed elsewhere in space.

If scientists were to understand why this process occurs, and what specific factors are at work, it could play a valuable role in helping us better understand the impacts of climate change.  We’re a little bit closer to understanding this phenomenon than ever before, thankfully, thanks to the help of MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS).

The EAPS’ observations show that Earth releases heat into space not only from the surface of the planet, but the atmosphere as well.  As the temperature rises, more water vapor is present in the air, and this creates something of a heat trap in Earth’s atmosphere.  Referred to as “water vapor feedback,” it’s part of the planet’s greenhouse effect.  Water vapor feedback essentially counteracts the rate at which heat is released into space.

Putting This Theory to the Test

In order to test this theory, the team of researchers developed a model of our planet to simulate the process of the release of heat into space.  A center column in the Earth model can be heated to a precise temperature, and then the amount of heat/radiation that escapes out of the Earth model can be measured through an automatic calculation process.

During the testing process, the team applied different temperatures to see how each surface temperature affected the amount of heat released from the model.  It didn’t take long to see a clear linear relationship between the surface temperature of the model and the heat released outward. 

At this stage, the team simulated other atmospheric variables, including humidity (water vapor) and convection, and tested different levels to observe their impact on Earth’s release of heat.

The research team was finally able to determine that when our planet’s surface temperature rises, it becomes compelled to release heat into space.  Meanwhile, when water vapor accumulates, it traps heat at specific wavelengths instead, to create a greenhouse effect that reduces heat loss to some extent.

Comparing Earth to Venus

Something else that the researchers observed was the way in which Earth’s greenhouse effect compares to that of Venus.  During their experiments, they found that the linear relationship between Earth’s surface temperature and heat emission is no longer applicable when temperatures go beyond 80 degrees Fahrenheit.  After this point, Earth struggles to release heat at a rate to match that at which the surface warms.  The result would be heat getting trapped within the planet, rather than shedding to maintain a kind of equilibrium.  For the time-being, the surface temperature of our planet is closer to 53 degrees Fahrenheit.

Basically, if Earth’s surface temperature were to reach that point, the entire process would break down.  To better understand this possibility, the researchers looked to Venus.  It’s widely believed that Venus’ atmosphere and climate was once very similar to that of Earth, despite being in closer proximity to the sun.  It’s believed that once upon a time, Venus had so much water vapor that excessive heat was trapped within the atmosphere, unable to escape.  The result was the planet’s atmosphere getting so hot that oceans literally boiled away.

But, that’s not likely to happen any time soon.  The team estimated that for this to occur, global average temperatures on Earth would have to hover around about 152 degrees Fahrenheit.  And, it’s believed that climate change alone – the gradual heating of the planet – would not even be able to produce that effect. Instead, more major climate changes, like those related to changes in the sun rather than Earth, would be the catalyst.

A Better Understanding of Our Planet’s Climate

Through these observations, we’re able to see Earth’s greenhouse effect at work, on a larger scale than ever before.  Not only that, but we’re also able to better understand climate incidents that date back to prehistoric times.  For now, thankfully, our planet’s process of shedding heat is keeping life on Earth stable.

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