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My latest Mind and Matter column in the Wall
Street Journal is on the greening of the planet:
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.
This possibility was first suspected in 1985 by Charles Keeling, the
scientist whose meticulous record of the content of the air atop
Mauna Loa in Hawaii first alerted the world to the increasing
concentration of carbon dioxide in the atmosphere. Mr. Keeling's
famous curve showed not only a year-by-year increase in carbon
dioxide levels but a season-by-season oscillation in the
During summers in the Northern Hemisphere, the Earth breathes in
carbon dioxide as green plants (most of which are north of the
equator) absorb the gas and turn it into carbohydrate. In the
northern winter, the Earth breathes the gas out again, as the
summer's leaves rot.
Mr. Keeling and colleagues noticed that the depth of the breathing had
increased in Hawaii by 20% [by 1995] since the 1960s: The Earth was
taking in more carbon dioxide each northern summer and giving out
more each winter. Since the inhalation is done by green leaves,
they reasoned, the amount of greenery on the planet must be growing
larger. In the 1980s forest biologists started to report striking increases in the growth rates of trees
and the density of forests: in Douglas firs in British Columbia,
Scots pines in Finland, bristlecone pines in Colorado and even
tropical rain forests.
Around the same time, a NASA scientist named Compton Tucker
found that he could map global vegetation changes by calculating a
"Normalized Difference Vegetation Index" (NDVI) from the data
produced by a satellite sensor. The data confirmed Mr. Keeling's
suspicion: Greenery was on the increase. At first, this was thought
to be a northern phenomenon, caused by faster growth in the great
spruce and birch forests of Siberia and Canada, but the satellites
showed it was happening all over the world and especially strongly
in the Amazon and African rain forests.
Using the NDVI, one team this year reported that "over the last few decades of
the 20th century, terrestrial ecosystems acted as net carbon
sinks," i.e., they absorbed more carbon than they were emitting,
and "net greening was reported in all biomes," though the effect
had slowed down in recent years. see also here.
The latest and most detailed satellite data, which is yet to be
published but was summarized in an online lecture last July by Ranga Myneni of
Boston University, 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? 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.
In a comprehensive survey of the litertature on
this subject, which I recommend as a short cut to many of the
individual studies and the continent-by-continent details, Craig
Idso reaches the following conclusions:
In the ensuing report we present a meta-analysis of the
peer-reviewed scientific literature, examining how the
productivities of Earth's plants have responded to the 20th and now
21st century rise in global temperature and atmospheric CO2, a rise
that climate alarmists claim is unprecedented over
thousands of years (temperature) to
millions of years (CO2 concentration). Based on that
analysis, we find the following:
The productivity of the planet's terrestrial biosphere,
on the whole, has been increasing with time, revealing
a great greening of the Earth that extends throughout
the entire globe.
Satellite-based analyses of net terrestrial primary
productivity (NPP) reveal an increase of around 6-13% since the
There is no empirical evidence to support the
model-based claim that future carbon uptake by plants will diminish
on a global scale due to rising temperatures. In fact, just the
opposite situation has been observed in the real
Earth's land surfaces were a net source of
CO2-carbon to the atmosphere until about 1940. From 1940 onward,
however, the terrestrial biosphere has become, in the mean, an
increasingly greater sink for
Over the past 50 years, for example, global carbon
uptake has doubled from 2.4 ± 0.8 billion tons in 1960
to 5.0 ± 0.9 billion tons in 2010 (see figure below).
The observed global greening has occurred in spite of
all the many real and imagined assaults on Earth's vegetation that
have occurred over the past several decades, including wildfires,
disease, pest outbreaks, deforestation, and climatic changes in
temperature and precipitation, more than compensating
for any of the negative effects these phenomena may have had on the
There is compelling evidence that the atmosphere's
rising CO2 content - which alarmists consider to be the chief
culprit behind all of their concerns about the future of the
biosphere (via the indirect threats they claim it poses as a result
of CO2-induced climate change) - is most likely the primary
cause of the observed greening trends.
In the future, Earth's plants should be able to
successfully adjust their physiology to accommodate a warming of
the magnitude and rate-of-rise that is
typically predicted by climate models to accompany the projected
future increase in the air's CO2 content. Factoring in plant
productivity gains that will occur as a result of the aerial
fertilization effect of the ongoing rise in atmospheric CO2,
plus its accompanying transpiration- reducing effect
that boosts plant water use efficiency, the world's vegetation
possesses an ideal mix of abilities to reap a
tremendous benefit in the years and decades to