WALL STREET JOURNAL
MIND & MATTER
January 4, 2013, 9:40 p.m. ET.
How Fossil Fuels Have Greened the Planet
By MATT RIDLEY
” …What explains this trend? Man-made nitrogen fertilizer causes crops to grow faster, but it is having little effect on forests. 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.
Dr. Myneni reckons that it is now possible to distinguish between these two effects in the satellite data, and he concludes that 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.”