LPM’s Bill Burton and WAVE 3 meteorologist Tawana Andrew talk about how the Earth creates a budget during this Science Behind the Forecast.
This transcript, which is from an archival episode of the series, was edited for clarity and length.
Bill Burton: It is time for us to take a look at the Science Behind the Forecast as I’m joined by WAVE 3 meteorologist Tawana Andrew. Good morning, Tawana.
Tawana Andrew: Good morning. I think this topic for today may make some people think about their wallets and their budgets a little bit differently.
BB: I think it definitely will. It's that time of year where we do think about budgets, when we start planning for the next year. It turns out the Earth is planning its energy budget as well. What do we need to know about the Earth's energy budget?
TA: This is so important to the way our weather and climate works. We have all of this radiation being beamed down to our planet every single day from the sun. And the balance between the incoming and outgoing radiation is called the energy budget. When you have more radiation being absorbed by our planet then released into space, that is when average temperatures across the region and across the planet rise.
There's a couple of scenarios in which we see a little bit more of those average temperatures increasing. First, when you have greenhouse gasses accumulating in the atmosphere, what those do is they basically trap the heat and the energy that otherwise would have dissipated in space. Another scenario is when you have sea ice, which is usually an amazing reflector of solar energy, and it's something meteorologists and climate scientists watch very closely, especially when it comes to our climate overall, because once it melts or it disappears, you end up with a situation where more of the ocean water is absorbing the heat and less of that energy is being reflected back out into space.
It's important to know that the majority of the energy used in our planet's climate comes from the sun. On average, you have about 340 watts per square meter of sunshine beaming down onto our planet. That's a lot of energy. Just compare it to your household light bulb, that's typically between 25 and 100 watts.
BB: That's a bit of a difference.
TA: That's a lot of energy. The majority of that energy is reflected back into space by our clouds, snow, dust and ice across the planet. The rest of it, about 240 watts, is absorbed mostly by the planet's surface, then about a quarter of that is absorbed by the atmosphere. The majority of the energy from the sun that is absorbed by our planet is actually radiated back into space. So think about during the daytime, all of that energy is being absorbed by the surface, and that's why our temperatures warm up incredibly. But at night, especially when we have those clear skies, all the energy is going back out into space, and that allows our temperatures to drop. That's one way to think about how the energy is absorbed and radiated back out, and how that balance needs to be met.
Most of the energy that reaches the surface, from our atmosphere and our sun totals about 500 watts, and just about 80% of that is emitted back into space. The rest of it, that last 20%, is so important because it helps to warm our air. Helps our temperatures rise. Otherwise we'd be super cold all the time. It helps the water warm up as well, and it helps the land warm up.
