The sun provides a lot for us. Probably more than we may realize. While it does give us light (this is helpful for us to see), it also gives us heat, as well as helps plants with the process of photosynthesis, which gives us air to breathe as well. But not all of the sun’s energy makes it to the surface of the earth. If this were the case, we would be the next grill item for a backyard barbecue! Let’s break down what is known as the energy budget, and how much of this we actually get to keep.
To start, the sun gives off a lot of energy. Like a lot, a lot (for anyone who wants a number, it’s 38,460 septillion watts or 3.846×10^26 per second). However, that is the amount for the entire sun. We are a small planet compared to the size of the sun, so we only get a tiny fraction of this energy directed towards us. But for simplicity, let’s just say the sun send energy to us at 100% (this will be easier to follow utilizing fractions).
Once the sun’s rays reach our planet, our atmosphere helps protect us from the dangerous UV rays. So instead of being blasted off course completely, we just get sunlight and heat, which helps dictate the temperatures in the environment. But the planet only absorbs about 52% of the sun’s energy makes it to the surface of the planet. The other 48% is either reflected back into space, or is absorbed by the clouds, water vapor, and dust in the atmosphere.
Since we only keep a little over half of the energy the sun gives us, plenty of items need to utilize this energy for life. 46% of the total energy is absorbed into the land and the oceans on the planet, while the other 6% gets reflected back to the atmosphere.
How does that 6% get reflected back? Why doesn’t it all get absorbed? Albedo. A term describing the different types of reflectivity of the energy, different environments have different albedo levels. For example, the roads we drive on will absorb 95% of energy and reflect 5% back to the air. But a desert will only absorb 55% of the energy and send the other 45% back to the atmosphere. And snow, which has a higher albedo (think of snow as the opposite of black top roads in this case) will only absorb 10% of the energy and reflect back 90%.
Another way to explain this is wearing certain colors of shirts during the year. In the colder winter months, wearing darker colors helps because they absorb light better, keeping us warmer. Wearing white or lighter color shirts during the summer helps reflect the energy, therefore, keeps us a bit cooler (although it may not seem like it sometimes).
Clouds also play a role as they not only reflect the energy back towards space, but they can also help trap the heat from escaping as well. When we have cloudy nights, the heat and energy is trapped, and keeps our temperatures warmer for the area. During the day, clouds will keep us cooler, since they are clusters of ice crystals and water droplets, which is lighter in color.
One last component to think about. The greenhouse effect. Our ozone layer helps with keeping our temperatures from completely escaping to oblivion (literally, space goes well beyond our research and imaginations at this point). The ozone layer in the atmosphere is similar to a greenhouse. It can allow sunlight and energy to come into the atmosphere, but not too much, rejecting the over-abundance we don’t need. But it also keeps our water and heat from escaping the planet too fast, leaving us (literally) in the cold.