Earth as a Greenhouse


My plan for Thursdays’ climate science posts is to prove a negative: that global warming can’t not be happening.

Here’s the thing, though. I don’t understand the science behind it well enough to start proving negatives yet.

That’s why I’m going to take you through the science first and understand it myself, before I start eliminating all other possible reasons for the average global conditions we’re seeing today.

Throughout these posts, if you think something needs clarifying or if I’ve gotten something wrong, please don’t hesitate to let me know.

First up for discussion is the greenhouse effect, the most important term you’ll ever hear in relation to global warming.

greenhouse1The greenhouse effect is named after—shockingly—greenhouses.

One major misconception about climate science is that the greenhouse effect behaves exactly like an actual greenhouse.

It’s a little more complicated than that. But for the purposes of this post, the metaphor works.

You might have heard of Bill Nye. Yes, you called it—the Science Guy.

He’s very active in the global warming debate. (Though there shouldn’t really be a debate.) He published a book called Unstoppable, in which he details the causes and effects of global warming. It’s where I’m getting most of my information at the moment.

The purpose of a greenhouse is to keep the plants inside warm. Sunlight is allowed to penetrate the glass walls and warm up the inside. However, hotter wavelengths of light find it impossible to get out.

That heat is trapped inside, all the while visual wavelengths travel right back to our eyes—letting us see through the glass of the greenhouse.

Not all the heat gets trapped inside. If that were the case, the plants inside would get too hot.

So how does this apply to the planet Earth?

gheffectThe Earth’s atmosphere behaves like the glass of the greenhouse. The metaphor isn’t perfect, but it basically works.

The sun shines through the atmosphere. Some solar radiation is absorbed by the earth, some is reflected off the surface and into the atmosphere, and some is reflected off the atmosphere entirely.

Of the radiation that is reflected off earth’s surface, some of it is reflected right back to earth’s surface by certain molecules—known as greenhouse gases—in the atmosphere.

Greenhouse gases include carbon dioxide, methane, nitrous oxide, and water vapor. The main culprit for global warming is carbon dioxide.

But why is all of this a problem, again?

Oh, right…did I forget to explain that part? Sorry about that. Well, for a simple explanation, let’s take a look at Venus.


This planet is our twin in every way save for its atmosphere. See, Venus’s atmosphere is extremely thick with greenhouse gases. It holds in most of the heat from the sun that reaches it.

The result: the planet’s surface is hot enough to melt lead.

That’s not to say we don’t need the greenhouse effect. Without it, Earth would sit at an average global temperature of about -18℃—which is just under 0℉. The greenhouse effect keeps the Earth habitable.

But…we don’t want to let it get too strong. Venus is a prime example of the consequences for that.

Then, the next logical question is, is it getting too strong?

The answer: Yes!

Remember how I said that carbon dioxide is a major greenhouse gas? Well, this is what’s happening to it.


Let’s take a close look at this graph.

The more carbon dioxide there is in the atmosphere, the more heat is held in. The Earth’s climate fluctuates naturally over a period of approximately 150,000 years—according to this graph.

When carbon dioxide levels are high, average global temperatures are warmer. When carbon dioxide levels are low, average global temperatures are cooler.

Now, let me be clear for a moment. Carbon dioxide is by far not the only variable controlling Earth’s climate. Variations in the Earth’s orbit are responsible for natural ice ages and interglacials—the time between the ice ages.

Also, allow me to clarify that climate is not the same as weather.

Weather is, according to Bill Nye, what happens day to day in one place. Climate is what happens over many years to a large geographical area, or the planet as a whole.

Political cartoons like this drive me crazy…


Weather is hard to predict. My grandma and I used to have a joke—that the weathermen were never right. Fact is, with constantly changing weather patterns…I can’t blame the weathermen if they get the course of a storm off by a couple miles.

But climate? You can accumulate a lot more data for that. The advantage of trying to predict the overall climate is that you can look at overall trends—like this.


The green line indicates a bunch of different data points. As you can see, temperatures keep fluctuating up and down. So how can we possibly predict what will happen next?

Well, it’ll be hard to predict the next monthly averages, or even the next yearly averages, but ten years from now? Twenty? All we have to do is look at that red average line.

And honestly, it shouldn’t be that hard to see that even if you look at the blue average lines—which aren’t the right way to take averages—temperatures appear to be climbing like stair steps. Not the best argument for deniers, if you ask me.

Anyway…let’s get back to carbon dioxide. So we know that carbon dioxide levels affect how much heat from the sun the Earth holds in. Those levels vary over time with Earth’s climate. But do me a quick favor and refer back to that carbon dioxide graph.

Or better yet, I’ll duplicate it for you here.

Version 3

For hundreds of thousands of years, carbon dioxide levels have fluctuated neatly between certain minimums and maximums. In 1950, those levels started to skyrocket unnaturally. And that trend continues.

The issue of the greenhouse effect isn’t that we have a greenhouse effect. We need a greenhouse effect. The issue is that we have too much of it.

But why?


Seems to me this image is everywhere on the Internet…

It depicts the emission of fossil fuels. What are fossil fuels, exactly? Coal, oil, and natural gas. Basically, all the stuff we use to power industry. That’s the main problem with taking steps to stop global warming. All of industry depends on fossil fuels.

When we burn the fossil fuels we extract from the ground and get energy, we release greenhouse gases into the atmosphere. The burning of coal results in the emission of carbon dioxide.

And that’s okay, mind you. We just don’t want to emit too much of it. We’d hate to end up like Venus, with our surface hot enough to melt lead.

Here’s the thing, though. We’re already emitting too many fossil fuels. That’s why climate science activists—including me—are raising our voices to transform industry and use cleaner forms of energy.

You know, like wind, water, and sun.

I’ve already used this image in my post, “How it Doesn’t Work,” but I love it so much that I’ll use it again here. I think this image is very thematic of global warming.


What I love most about this image is that it’s very dark and red, almost like the inferno of hell, but the sun and the windmills stand on the horizon, waiting to take action. All this image needs is a water turbine and it’ll be complete.

All this to say, there are cleaner, better forms of energy than fossil fuels. We don’t have to break our backs—and then our planet—mining coal.

Instead, we can use wind and water to power industry. And solar panels are already quite common—they’re all over the rooftops. There are some large businesses that are beginning to—or already have—constructed large fields of solar panels.

Don’t listen to powerpoint slides like this.


They basically ignore that the burning of fossil fuels will kill the planet, and this one can’t even spell right. (Sorry, pet peeve of mine. Comes from being a writer.)

The deceptive thing about the argument presented here is that it’s completely true. However, it doesn’t list the disadvantages—global warming—and, naturally, excludes arguments for other forms of energy. Which are strong.

Next up on this blog is an examination of false news sites, compared to trustworthy ones. See you around!

About Emma

I'm a college student, astronomer, writer, Democrat, global warming activist, hardcore trekkie, daring adventuress, and dreamer. I write for different reasons. Sometimes because I want to share my process of discovery with others. Sometimes because I think a story is too incredible to keep it to myself. Sometimes just because I want to be heard. Regardless, I hope you enjoy it!
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