Atmospheric Carbon Dioxide and the Greening of the Planet

Atmospheric carbon dioxide (CO₂) levels have been changing globally since about 1785. Ice core samples indicate that prior to the late 1700s, CO₂ levels were around 280 parts per million (ppm). In 1885, CO₂ levels peaked at 293 ppm as a direct result of the Industrial Revolution, a period powered by coal combustion. As industrialization continued worldwide to include fossil fuel cars and electric power plants, CO₂ levels rose to 349 ppm. In 2014, CO₂ levels reached 400 ppm, and today, atmospheric levels are hovering around 416 ppm.

Carbon dioxide levels are often associated with climate change, but this is just one piece of the puzzle. How are changing atmospheric CO₂ levels impacting the cycling of carbon in the hydrosphere, geosphere, and biosphere? One method used to examine the interactions between atmospheric carbon dioxide and the biosphere is to measure global leaf cover. Since plants absorb CO₂ from the atmosphere during photosynthesis, it can be hypothesized that as CO₂ levels increase, leaf cover should increase. Using satellite imagery, scientists can study the relationship between atmospheric carbon dioxide and global leaf cover (as seen in the map below).

In this activity, students use data from 2015 through 2020 to build on the model shown in the map below. They are asked to modify the model presented for 2015 to explain predicted leaf cover for 2016, 2018, and 2020 after calculating percent change in atmospheric carbon dioxide levels.