A recent paper on
planetary 'greening'
should have been
front-page news.
But good news
on climate science
does not get any
mass media
coverage !
The study appeared
in the journal
“Higher than expected
CO2 fertilization
inferred from leaf to
global observations”,
is by Vanessa Haverd
( of Australia’s CSIRO ),
and eight coauthors.
They use
a biophysical model
and observed climate
to back-calculate
global primary
productivity ( GPP )
( GPP is the net change in
standing vegetation per year ),
and to forward-calculate it
using climate model forecasts.
"The rate of carbon fixation
by photosynthesis—
is estimated to have risen by
(31 ± 5)% since 1900."
That's almost double
the previously accepted
1900-2006 increase in GPP
of 17% +/- 4%.
"These findings suggest
a larger beneficial role
of the land carbon sink
in modulating future excess
anthropogenic CO2
consistent with the target
of the Paris Agreement
to stay below +2°C warming,
and underscore the
importance of preserving
terrestrial carbon sinks.”
The paper predicted
that the earth is
going to gain nearly
three times as much
green matter as was
forecast in the last
(2013) IPCC report.
Haverd’s model
reproduced the
satellite-sensed
changes in
leaf area index
shown by
Zhu et al. (2016),
which found the
greatest greenings
to be in the world’s
semiarid tropics,
tropical forests,
and a smaller
( but significant )
increase in
temperate latitudes.
Two radically different methods
—satellite sensing (Zhu), and a
biophysical model (Haverd) --
both say we are greening
the earth fast, especially in
critical tropical ecosystems.
The emissions scenario
in Haverd is the UN’s
Representative Concentration
Pathway (RCP) 2.6 for
future CO2 emissions,
the IPCC's lowest estimate.
RCP 2.6 is associated with
+2.4⁰C of warming by 2100.
( since pre-industrial times )
The goal of the Paris
Agreement is to hold
warming to +2 degrees C.,
or below.
With RCP 2.6,
which is possible,
but not likely,
the greening Earth
( the increase of plants )
could pull so much
more carbon dioxide
out of the air
as plant food,
that we could meet
the Paris Accord
from the 'greening'
of our planet !