Why are the colors different on the planet at different times of the year ? Give a specific example.

In the Northern Hemisphere, ecosystems wake up in the spring, taking in carbon dioxide and exhaling oxygen as they sprout leaves — and a fleet of Earth-observing satellites tracks the spread of the newly green vegetation.

Meanwhile, in the oceans, microscopic plants drift through the sunlit surface waters and bloom into billions of carbon dioxide-absorbing organisms — and light-detecting instruments on satellites map the swirls of their color.

Satellites have measured the Arctic getting greener, as shrubs expand their range and thrive in warmer temperatures. Observations from space help determine agricultural production globally, and are used in famine early warning detection. As ocean waters warm, satellites have detected a shift in phytoplankton populations across the planet's five great ocean basins — the expansion of "biological deserts" where little life thrives. And as concentrations of carbon dioxide in the atmosphere continue to rise and warm the climate, NASA's global understanding of plant life will play a critical role in monitoring carbon as it moves through the Earth system.

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