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Earth is Becoming a Greener Greenhouse Changes in Growing Season Duration: We define growing season as the number of days with greenness level greater than a threshold value and assess changes in the duration of photosynthetic activity. For a threshold value of 0.3, the beginning of spring advanced by about 8 ± 4 days in North America and 6 ± 2 days in Eurasia from 1982 to 1999. Similarly, the termination of activity in autumn was delayed by 4 ± 3 days in North America and 11 ± 3 days in Eurasia. Therefore, the duration of the active growing season (see the figure below) increased by about 12 ± 5 days in North America and 18 ± 4 days in Eurasia. |
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Sep-04-2001 |
