Large volcanic eruption of Mt. Pinatubo in 1991 slowed CO2 buildup for several years.
But the carbon dioxide record isn’t immune to temporary dips lasting several years or more. A slowdown occurred in 1930–36 after the Great Depression and again during the 1940s, possibly because of World War II. The large volcanic eruptions of Mt. Agung (Indonesia) in 1963 and Mt. Pinatubo (Philippines) in 1991 each slowed CO2 buildup for several years. Volcanic emissions cool the lower atmosphere and scatter sunlight. Those changes can both reduce plant respiration, a process that releases carbon dioxide, and boost photosynthesis, which removes carbon dioxide from the air. “Atmospheric CO2 growth is best reflected by the world population trend,” said Hofmann. “The two have tracked each other extremely well over the past century. A break in the close relation between population growth and CO2 growth would be a clear sign of progress in the inevitable need to limit atmospheric CO2.”NOAA understands and predicts changes in the Earth’s environment, from the depths of the ocean to the surface of the sun, and conserves and manages our coastal and marine resources.