You likely noticed that carbon dioxide and temperature have followed similar trends throughout history.

Question: How might changes in temperature and carbon dioxide concentrations affect each other?

A major source of carbon dioxide is plant and animal respiration. Increases in global temperatures affect the density of plant and animal life on the planet. An increase in temperature can increase the number of living CO₂ sources on our planet.

Now let's think about the factors that influence Earth's surface temperatures. You can learn about how concentrations of heat-absorbing gases (ie. CO₂) in the atmosphere can affect global temperatures in lessons 3 and 4. If carbon dioxide concentrations increase, the average global temperature may also rise.