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 U.S.–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 was our 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 return 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 such as carbon dioxide 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!