But the 20-year data gathered from NASA's Earth-to-Two Satellite instrument has succeeded in showing that human activity in China and India dominates the greening of the planet.
"These long-term data allow us to dig deeper," said Rama Nemani, a NASA scientist at California.
"When we first observed the greening of the Earth, we thought it was due to a warmer, wetter climate and fertilization of the added carbon dioxide in the atmosphere, leading to more leaf growth in the northern forests, for example.
Now, with 20 years of data, he said, "It allows us to understand the phenomenon at really small scales, [and] we see that people are also contributing. "
China has contributed most to the greening of the Earth before India and then to the European Union, respectively, for Canada, Russia, Australia, the United States and Mexico.