Science Scoops: And…Reflections of Earth's Climate
by Stephen James O'Meara
Wondering how Earth's climate may be changing over the years? Well, how about keeping an eye on the Moon? Yup. That's what researchers did in the late 1920s, and that's what Philip R. Goode (New Jersey Institute of Technology) and his colleagues did more recently. Actually, Goode and his team are not directly watching the Moon. Instead, they're watching sunlight that has been reflected off the Earth and onto the Moon's “bright” side when it just happens to be in shadow, a phenomenon called “earthshine.” You see earthshine best when the Moon is in a crescent phase; it's the “old Moon in the new Moon's arms.” In essence, the scientists are using the Moon as a mirror, one that will reflect changes in Earth's atmosphere.
Here's how it works. The amount of sunlight our planet bounces back into space reflects how much cloud, atmospheric dust, and snow is covering the Earth. Any radiation not being reflected is being absorbed. This means that if the Earth isn't being as reflective as normal, Earth's climate must be getting warmer.
As reported in Sky & Telescope magazine, Goode says that on average the Earth reflects 30 percent of the sunlight hitting it. But recently our planet seems to be a bit brighter than it was in 1994–95. What does this mean?
Is the Earth getting colder?
Well, stay tuned, because the earthshine measurements will have to continue for many more years before the researchers can draw any conclusions.
- In Lesson 2, you studied a diagram that showed the phases of the Moon as viewed from Earth. Why do you think that earthshine is brighter when the Moon is in a crescent phase? Write a sentence or two explaining your answer.
[anno: Answers will vary but could include that because a smaller portion of the Moon is lighted during a crescent phase, a variation in that amount of light might be more noticeable.]
- What are some of the other ways that people use or have used the phases of the Moon? List a few ways that people have used phases of the Moon.
[anno: Answers will vary but could include that some people have tracked time using the phases of the Moon. Some people believe that the full Moon causes strange things to happen, and they might alter their plans because of a full Moon.]