Cordell Grant might be a rocket scientist, but you have to be to understand the science behind climate change.
While people have been led to believe that climate science is so complex that nobody can understand it, he says that’s simply not true. In this multi-part series, Climate Change Ain’t Rocket Science, he sets out to prove that, by breaking down the fundamental scientific principles in a way anyone can understand.
Part 5: Earth's Temperature
To summarize Parts 2 to 4, heat is coming into the Earth from the sun and leaving Earth via albedo and thermal radiation. Armed with various properties of the Earth and sun we have enough information to do a basic calculation of what the average temperature of the Earth should be.
We plug our numbers into a somewhat scary but relatively straightforward equation called the Stefan-Boltzmann Law (see Note 1) and we get an average temperature for the Earth of ... TOO COLD.
That's right, our calculation produces a result that makes no sense because it is significantly colder than we know the Earth actually is. Parts 6, 7 and 8 will cover what is missing from our calculations.
Note 1: For the ultra-nerdy (such as myself), Stefan-Boltzmann Law states that the total radiant heat power emitted from a surface is proportional to the fourth power of its absolute temperature. This is the only place I've ever seen Pi raised to the fifth power.
Part 6: The Electromagnetic Spectrum
We haven't mentioned it yet, but all of the heat being radiated around the universe is carried in the form of light. Light comes in lots of varieties, many of which we've all heard of.
Visible light is what our eyes can see. Ultraviolet gives us sunburns. X-rays show us our bones and teeth. Light can be thought of as a wave, and the difference between all of these types of light is their wavelength.
Remember ROYGBIV (the colours of the rainbow)? Each colour in the rainbow represents a different wavelength of light. At one end is R = Red and at the other end V = Violet. Red has a longer wavelength than violet.
Going beyond the colours of the rainbow, if your wavelength is somewhat shorter than violet, you're into the ultraviolet. Get shorter still and you get to X-rays.
In the other direction, if your wavelength is somewhat longer than red, you're into the infrared. Keep getting longer and you stop calling it light and start calling it radio. But it's fundamentally all the same thing.
Collectively, all the different varieties/wavelengths of light are called the electromagnetic spectrum.
Part 7: Invisible Light
You may be wondering why I spent all of Part 6 explaining the electromagnetic spectrum.
Let's take a moment to think about the implications. From Part 2 we know that every object in the universe is radiating heat all the time. And from Part 6 we now know that radiated heat takes the form of light. Put those two together and it means that you, and everything around you, are constantly emitting light.
So why can't we see this light?
It turns out that the wavelength of light that an object radiates depends on its temperature. Shorter wavelengths (higher frequency) take more energy to generate. Hot objects have more energy than cold ones. So the hotter an object is, the shorter the wavelength.
For example, anytime you turn on your oven you see the element get "red hot." It's tempting to think that's the point where the element starts emitting light. What actually happens is that as the element heats up, it reaches a temperature where the light it emits enters the visible part of the EM spectrum. It was always glowing, just not with light your eyes could see.
The sun is much hotter than the element on your stove. Its light spans the entire visible part of the EM spectrum and beyond into the UV (we wouldn't need sunblock if it didn't).
Earth, on the other hand, is much cooler than the sun. It emits light in longer wavelengths, specifically, the infrared. If astronauts had infrared eyes they would see the Earth glowing beneath them like a gigantic light bulb as its heat escapes to deep space. It's that same infrared light that night vision systems and thermal imagers use to see in the "dark."
At this point you may be asking yourself what any of this has to do with climate change. Part 8 will make that clear. But for now, the most important thing you need to take away from Part 6 and Part 7 is that the heat coming from the sun arrives at one set of wavelengths (mostly visible) and leaves Earth at a different set of wavelengths (infrared). Understand this and the rest is easy.
Cordell Grant is an aerospace engineer — or rocket scientist — from Howie Centre who now lives in Toronto with his wife and two children. Although he isn’t a climate scientist, his work building satellites has made him something of an expert in the subject — after all, Earth is really just a big satellite that orbits the sun. His Climate Change Ain’t Rocket Science multi-part series will run each Saturday in the Cape Breton Post.
