Why Methane Matters

Why Methane Matters

Have you ever noticed what happens to your cup of hot chocolate when you walk away?  It cools down, right?  Similarly, everything in the universe does the same.  Think of anything you want: your car, dog, even that fluffy bunny.  If they have a temperature, they generously share that heat with the rest of us.  It’s called radiation, and we’re all doing it, all the time.  The hotter you are, the more heat you radiate away.  In fact, if one object is twice as hot as another, it actually radiates 16 times as much heat away!  The sun is REALLY hot and radiates a lot of energy, which the reason we have this comfortable planet to live on.  The surface of the earth absorbs much of the sun’s energy and, in response, it warms.  As it warms, more heat is radiated away until it reaches the temperature where the radiation from the surface matches the energy absorbed from the sun.  Not all radiation is created equal.  Hotter objects also radiate different types of light.  As an object warms, it tends to radiate more of the super fast, short wave light (UV) and less of the slow, long wave light (IR).   At the sun’s temperature of around 5,000 Celsius (9,000 F), its favorite type of light is that middle ground, what we call the visible spectrum, from red to blue.   

Wondering what role the atmosphere plays in this energy balance?  Like the surface, the atmosphere is hungry for energy and absorbs whatever light it can.  Those nimble short waves waves from the sun are tough to catch and slip right through but the big and slow IR radiated from the surface is easy prey for the atmosphere, and much of the radiation leaving the earth is trapped by the atmosphere and sent back to the surface, resulting in more warming.  That’s what we call the greenhouse effect.  It’s also the reason your car gets so hot in the summer – visible light sneaks right through the windows and heats the seats, which radiate IR light – which doesn’t sneak through the windows but instead remains trapped inside.   

The ability of the atmosphere to trap IR light depends on a few things – mostly which gases are in the atmosphere.  There are a bunch of gases, known as greenhouse gases, that are especially good at trapping this energy. CO2 is the most famous among them, but methane is close behind.  These greenhouse gases are powerful guardians against IR radiation – they stop it from passing in both directions.  Without any greenhouse gases in the atmosphere, we’d be a cold planet (about 25°C colder than we are now).  But much like chocolate, too much of a good thing is not good for us, and if we continue to add greenhouse gases to the atmosphere, we will continue to warm the planet.  Water in the atmosphere is the most important greenhouse gas, but it’s also one that we don’t have much control over.  Next, after water is CO2, which represents about 0.04% of the atmosphere.  There is about 200 times as much CO2 in the atmosphere as methane, but methane has a powerful trick up its sleeve – each molecule of methane can absorb about 80 times as much energy as CO2.  So, why does methane matter?  Methane matters because of its potential to warm the planet.