Last September, researchers used satellite data and confirmed that plant life has been growing more vigorously since 1981 above 40 degrees north latitude, which represents a line stretching from New York to Madrid to Beijing. They also determined that the growing season has increased by several days, especially in Eurasia. One suspected cause of this "greener greenhouse" they cited was rising temperatures that are possibly linked to the buildup of greenhouse gases in our atmosphere.
"When we looked at the data between 1992 and 1993, the warming period of the last 20 years was interrupted because of the tiny dust particles (aerosols) shot into the atmosphere by the eruption of Mount Pinatubo," said Ranga Myneni, co-author of the study, and professor at Boston University. The increased amount of aerosols cast into the upper atmosphere from the eruption caused more sunlight to be reflected back into space and cooled the Earth.
As a result of the Earth cooling, and sunlight being reduced, plants produced less new foliage, because they use sunlight, carbon dioxide and water to make sugars for growth of new stems, leaves and structures. Myneni said that the computer model he and his colleagues used simulates photosynthesis, and calculates the amount of plant sugars that are produced versus how much carbon is given off.
During the 1980s and 1990s the land was taking in more carbon than it was putting back in the air, including the years immediately following Mt. Pinatubo's eruption. "That is because although the plants produced l
Contact: Rob Gutro
NASA/Goddard Space Flight Center