How Global Warming Works: Climate Change's Mechanism Explained
by Professor Michael Ranney, Dr. Daniel Reinholz, and Dr. Lloyd Goldwasser (with help from Professor Ronald Cohen)
You may have heard of global climate change, which is often called “global warming.” Whether or not people accept that humans are causing global warming, most folks have an opinion about it. But how much do regular people understand the science of climate change? If you were asked to explain how global warming works, could you? Take a moment to try to explain to yourself how virtually all climate scientists think the Earth is warming. What is the physical or chemical mechanism?
Don’t feel bad; if you’re anything like the people we’ve surveyed in our studies, you probably struggled to come up with an explanation. In fact, in one study, we asked almost 300 adults in the US––and not a single person could accurately explain the mechanism of global warming at a pretty basic level. This is consistent with larger surveys that have shown that people often lack knowledge about climate change. But how can we make informed decisions without understanding the issues we’re debating?
Allow us to give you a short explanation of how global warming works:
First, here is how Earth’s temperature works without considering how humans influence it: The Earth absorbs light from the sun, which is mostly visible light. To release that light-energy, Earth also emits light. But because the Earth is cooler than the sun, it emits lower-energy, infrared light. So Earth's surface essentially transforms most of the visible light it gets from the sun into infrared light. Greenhouse gases in the atmosphere, such as methane and carbon dioxide, let visible light pass through, but absorb infrared light––causing the atmosphere to retain heat. This energy can be absorbed and emitted by the atmosphere many times before it eventually returns to outer space. The added time this energy hangs around has helped keep Earth warm enough to support life as we know it. Without this “greenhouse effect”––caused by these greenhouse gases in the atmosphere––the Earth’s average surface temperature would be about 50 degrees Fahrenheit cooler, which is well below the freezing point for ice!
So, how have humans changed things? Since the dawn of the industrial age, around the year 1750, atmospheric carbon dioxide has increased by 40%––and methane has almost tripled! These increases cause extra infrared light absorption, meaning an extra greenhouse effect, which has caused Earth to heat above its typical temperature range. In other words, energy that gets to Earth has an even harder time leaving it, causing Earth’s average temperature to increase––thus producing global climate change.
In case you’re wondering about what makes greenhouse gases special, here are two sentences of slightly technical information: Greenhouse gases absorb infrared light because their molecules can vibrate to produce asymmetric distributions of electric charge, which match the energy levels of various infrared wavelengths. In contrast, non-greenhouse gases, such as oxygen––that is, O2––don't absorb infrared light, because they have symmetric charge distributions even while vibrating.
To wrap up, we’ll quickly summarize the mechanism of global climate change: Earth transforms sunlight’s visible energy into infrared light, and infrared energy leaves Earth slowly because it’s absorbed by greenhouse gases. As people produce more greenhouse gases, energy leaves Earth even more slowly––raising Earth’s temperature even more than it has already gone up. That’s how global warming happens!
This wasn’t so hard to understand, right? In these few minutes you’ve hopefully become one of the few people who understand the mechanism of global climate change! Please share this video with others so you can help them understand how global warming works, too. Thanks for listening!