The greenhouse effect keeps Earth warm. Play NOVA's Polar Lab to find out what too much CO2 in our atmosphere may mean for our planet.
How Carbon Dioxide Warms Planet Earth
Published: February 25, 2020
Caitlin Saks: Have you heard of the greenhouse effect? CO2 is a greenhouse gas. Here’s how it works: The Sun sends a lot of energy towards the Earth. The Earth radiates energy back out into space, but some of that outgoing radiation gets trapped, warming our planet. One of the biggest factors in determining how much energy gets trapped is the concentration of greenhouse gases, like carbon dioxide, in our atmosphere. The higher the levels of these energy trapping molecules, the warmer our planet gets.
Over the last 800,000 years, the concentration of CO2 in the atmosphere has cycled between 180 and 280 ppm.
But if we extend the CO2 graph forward to the present day, you’ll see an extreme increase in the past couple hundred years. This is especially true over the last 60 years, since we’ve been able to directly measure the carbon dioxide in our atmosphere.
Christo Buizert: So not only is CO2 higher now than it has been during the last million years, the rate at which it’s going up is also much faster than it has ever done in the past, about 100 times faster than it ever has during the last million years.
Caitlin Saks: Today, CO2 levels are over 400 ppm. The last time they were this high was about 3 million years ago when there was little ice in the Arctic, and the east coast of North America was underwater! Those changes can’t happen overnight, but we’re already starting to see things shift.
Julie Brigham-Grette: If you warm things up it takes a while for the pollen to move northward, to then grow plants. If you look at places in the tundra today, we’re starting to see more shrubs. And as the shrubs grow, the trees start to migrate northward. And it might take another thousand years for the forest to come back around Lake El’gygytgyn.
Caitlin Saks: The orbital cycles trigger the planet’s warming and cooling over the past million years. CO2 amplifies that pattern, really helping to drive those glacial-interglacial cycles. Scientists are still trying to figure out how the orbital cycles and fluctuations in CO2 are related, but one thing is clear: the amount of CO2 in our atmosphere determines how much ice is on our poles.
Hosted by: Caitlin Saks
Production by: Ari Daniel & Lorena Lyon
Camera: Emily Zendt
NOVA Labs Editorial Director: David Condon
Additional Visuals: Mitch Butler, NASA's Goddard Space Flight Center, Shutterstock, Videoblocks
© 2020 WGBH Educational Foundation