This data plot shows the monthly mean carbon dioxide of the Mauna Loa volcano from roughly 1960 to the present day.

In 1958, Charles David Keeling went to the Mauna Loa Observatory in Hawaii and began measuring the levels of carbon dioxide present.  As the data in the graph above shows, the amount of carbon dioxide parts per million (ppm) has increased steadily and dramatically from roughly 1960 to 2020.  In what came to be known as the Keeling Curve, the Mauna Loa data shows that the amount of carbon dioxide in the atmosphere is increasing.  By 2012, atmospheric CO2 had risen by 25% from the original recording.

Deforestation, the Industrial Revolution, and numerous other man-made factors have caused this acceleration of carbon dioxide into the atmosphere, but why does it matter?  Well, carbon dioxide and other greenhouse gases trap heat in the atmosphere.  As the sun shines down on Earth, some of the heat radiation is reflected back away from the atmosphere.  Global amounts of carbon dioxide, as demonstrated in the figure above, are increasing.  This means that more heat is being trapped and less is being reflected, causing the Earth’s atmosphere to become warmer.  This causes numerous potential problems for humans and other species as well.  The increased atmospheric temperature causes sea levels to rise because of the expanding water due to heat, and also due to glaciers melting.  A higher atmospheric temperature also lowers the pH of water, causing destruction to coral reefs and many marine habitats.  The rise in sea level will affect human beings because many places that are densely populated will soon be underwater if greenhouse gas emissions continue to rise like the figure shows.

Sources:

Molles, Manuel C., and Brendan Jonathan Borrell. Environment: Science, Issues, Solutions. W.H. Freeman, 2016.