It’s a question of whether we’re going to go forward into the future, or past to the back. -Dan Quayle
This is my last day writing before my spring break begins, and I’m hoping for some great weather as I prepare to head to the Oregon coast. Warm weather, clear skies… I can picture it now. In my dreams, it looks something like this.
It makes me think about global warming, the greenhouse effect, and whether this is really cause for concern or not.
On one hand, it’s definitely true that heating the planet up by even a few degrees will have catastrophic effects on our sea levels as the ice sheets over Antarctica and Greenland melt, displacing hundreds of millions of people and causing worldwide changes in the production of our food supply. For example, if the sea level rises by just 60 meters (that’s a partial melting of those ice sheets), all of the areas in red on the map will go from being (mostly habitable) land to being underwater.
Click to enlarge, of course, and note that huge sections of the U.S., India, China, England, and coastal Europe will be underwater. So that’s one hand.
But on the other hand, could changes to the atmosphere really be the cause of changes in temperature? In all honesty, it’s hard to answer that question just from looking at Earth.
Luckily, we have some other, nearby worlds to help shed light on our situation. Let’s take a look at the planets of the inner Solar System: Mercury, Venus, Earth, and Mars.
Mercury is the closest to the Sun, and gets awfully hot, topping out at about 450 Celsius (840 Fahrenheit) during the hottest part of the day & year. And as you might expect, of the four rocky planets we have to look at, Mars is the coldest. But if you look at the hottest part of Mars during the hottest times, it can get all the way up to about 27 Celsius (81 Fahrenheit), which isn’t too bad, considering how much farther away it is!
As you’d expect, Earth is cooler than Mercury but warmer than Mars. And I bet that you’d expect Venus — being closer than Earth but farther away than Mercury — would have temperatures in between Mercury’s and Earth’s.
Well. It turns out that Venus has an average temperature of about 460 Celsius (860 Fahrenheit), with no significant differences between day and night temperatures, even though a day on Venus lasts about 117 Earth days!
What gives? Venus is about twice as far from the Sun as Mercury, and therefore receives only about one-quarter of the energy from the Sun for each square mile of its surface as compared to Mercury.
So what gives? Why is Venus so hot? If you really want to know, all you have to do is look at Venus’ atmosphere. Take a look at the swirling clouds in the atmosphere, and you’ll immediately know something fishy is up.
Venus has an atmosphere that’s something like 93 times as thick as Earth’s, and over 96% of that atmosphere is carbon dioxide. That thick atmosphere lets lots of Solar Radiation (visible and ultraviolet light) in. When the planet tries to get rid of it — just like Earth does — it re-radiates that energy in the infrared. But carbon dioxide doesn’t let infrared light through very well, it reflects it back onto the planet’s surface.
This is how a greenhouse works, and that’s why it’s called the greenhouse effect!
This is a real effect, it really happens, and everyone agrees that this is the cause for why Venus is as hot as it is.
If everyone can agree on this, then the question isn’t whether putting carbon dioxide in our atmosphere is going to cause a greenhouse effect: it does. (And people contending otherwise, like this, are wrong, and now you know why.) The real question — the only one up for debate — is this: how much of an effect will adding carbon dioxide to our atmosphere cause?
Scientifically, it is no longer a question of whether global warming happens when you increase carbon dioxide in your atmosphere: it does. It’s now a question of how much carbon dioxide will lead to an unacceptable level of warming for Earth, and what — as the only species on the planet capable of doing something about it — we’re actually going to do.