Based on the Keeling Curve graph, what causes the annual rise and fall of carbon
dioxide levels in the atmosphere? In other words, why does the graph have a
zigzag pattern?
420
Mauna Loa Observatory, Hawaii
Monthly Average Carbon Dioxide Concentration
Data from Scripps CO, Program Last updated February 2020
CO₂ Concentration (ppm)
410
400
390
380
370
360
www
350
340
330
320
310
1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020
Year
O Oil refineries are shut down periodically in the summer
People use more energy in the winter