sexta-feira, Janeiro 25, 2013

the Earth is getting greener

The greening of the planet por Matt Ridley:
Did you know that the Earth is getting greener, quite literally? Satellites are now confirming that the amount of green vegetation on the planet has been increasing for three decades. This will be news to those accustomed to alarming tales about deforestation, overdevelopment and ecosystem destruction.
The latest and most detailed satellite data .. confirms that the greening of the Earth has now been going on for 30 years. Between 1982 and 2011, 20.5% of the world's vegetated area got greener, while just 3% grew browner; the rest showed no change.

What explains this trend? .. There are essentially two possibilities: climate and carbon dioxide itself. Warmer, wetter weather should cause more vegetation to grow. But even without warming, an increase in carbon dioxide should itself accelerate growth rates of plants. CO2 is a scarce resource that plants have trouble scavenging from the air, and plants grow faster with higher levels of CO2 to inhale.

.. 50% is due to "relaxation of climate constraints," i.e., warming or rainfall, and roughly 50% is due to carbon dioxide fertilization itself. In practice, the two interact. A series of experiments has found that plants tolerate heat better when CO2 levels are higher.

The inescapable if unfashionable conclusion is that the human use of fossil fuels has been causing the greening of the planet in three separate ways: first, by displacing firewood as a fuel; second, by warming the climate; and third, by raising carbon dioxide levels, which raise plant growth rates.

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