We all know that greenhouse gases are bad. And that climate change is bad and we need to stop emitting greenhouse gases by the end of the century or risk dire climate-related consequences, such as dramatic sea level rise, extreme weather events, and food shortages.

But what's the connection between emissions and these terrible scenarios? Bill Nye, The Science Guy, made the great video below a few years ago with Climate Reality that explains just that.

While greenhouse gases like carbon dioxide and methane naturally exist in the earth's atmosphere, when their concentration gets to be too high, temperatures rise, Nye narrates. For those who are skeptical that emissions can play a role, Nye put together a simple demonstration.

All you need are two jars, two thermometers, two heat lamps, and a source of carbon dioxide — for example, a carbon dioxide cylinder used to pump gas bubbles into homemade soda. Here's how it works: First, you take two identical bottles or jars and place a thermometer inside each one.

Next, run a hose from a source of carbon dioxide into one of the jars. Place a heat lamp over each jar and let them sit.

Watch the two thermometers: The temperature in the jar with the carbon dioxide will shoot up faster.

This is because greenhouse gases traps the heat from the light — just like the additional greenhouse gasses in Earth's atmosphere trap heat from the sun.

Speaking of the sun, another common confusion about climate change is the Sun's role.

Solar radiation from the sun — illustrated below as the green balls — hits the Earth and is absorbed the planet's surface and atmosphere, which then radiate the energy back out in the form of heat.

Greenhouse gases in the atmosphere — illustrated by the red balls — trap this heat and radiate it back down to the earth's surface.

This is why all the gases humans are pumping into the atmosphere are causing temperatures to rise, Nye explains.

Scientists say it's still not too late to avoid the worst consequences of climate change. The latest UN climate report urges a global carbon emissions cut of 40-70% by midcentury and an entire elimination by 2100 — a move they say is the only move that will keep global temperatures within 2 degrees Celsius of their historic levels. Beyond this point, many scientists believe a series of catastrophic climate effects could be set in motion.

"We've set this chain in motion," Nye says in the video, "but the truly cataclysmic changes can be prevented if we act now."

Check out the complete video below: