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CLIMATE-WARMING-SCIENCE
Geoengineering: ‘Plan B’ for the planet
PARIS, Aug 23, 2019 (BSS/AFP) – Dismissed a decade ago as far-fetched and
dangerous, schemes to tame global warming by engineering the climate have
migrated from the margins of policy debates towards centre stage.
“Plan A” remains tackling the problem at its source. But the UN’s top
climate science body has made it clear that slashing carbon pollution won’t
be enough to keep Earth from overheating.
That has opened the door to a host of geoengineering schemes, and an
under-the-radar set of global industry guidelines, currently in review, which
could help mainstream them.
Here is a menu of “Plan B” geoengineering solutions, and their potential
drawbacks:
– Direct CO2 capture –
Experiments have shown it is possible to suck planet-warming carbon
dioxide directly from the air, converting it into fuel pellets or storing it
underground.
A Canadian company backed by Microsoft co-founder Bill Gates launched a
pilot facility in Canada in 2015, and another company unveiled one in Iceland
last year.
DRAWBACK: The technology is currently prohibitively expensive and may take
decades to operate at scale.
– Afforestation –
Extensive planting of trees could significantly slow the concentration of
CO2 in the atmosphere, which currently stands at more than 410 parts per
million, 40 percent more than 150 years ago.
DRAWBACK: Even if deforestation could be reversed — more than 100,000
square kilometres of tropical forests have disappeared each year since 2013 –
– the number of trees needed to put a dent in CO2 emissions would clash with
food and biofuel crops.
– BECCS –
Bioenergy with carbon capture and storage (BECCS) marries a natural
process with a high-tech one.
The first step is to plant rapeseed, sugarcane, corn or “2nd-generation”
biofuel crops such as switchgrass, which pull CO2 from the air while growing.
The second step is while burning the harvested plants for energy to sequester
the CO2 produced.
In theory, the result is less CO2 in the atmosphere than when the process
started. Virtually all climate change models projecting a future consistent
with the Paris Agreement’s temperature targets assume a key role for BECCS.
DRAWBACK: Studies calculate that up to twice the area of India would need
to be given over to biofuels, putting BECCS in conflict with food crops.
– Ocean fertilisation –
Microscopic ocean plants called phytoplankton gobble up CO2 and drag it to
the bottom of the ocean when they die. Their colony size is limited by a lack
of natural iron, but experiments have shown that sowing the ocean with iron
sulphate powder creates large blooms.
DRAWBACKS: Scientists worry about unintended impacts. Die-offs of
plankton, for example, use up oxygen, which could create massive “dead zones”
in the oceans, something already on the rise.
– Enhanced weathering –
Natural weathering of rocks removes about one billion tonnes of CO2 from
the atmosphere every year — about two percent of total man-made C02
emissions.
Spreading a powdered form of a greenish iron silicate called olivine
across certain landscapes can mimic that process, experiments have shown.
DRAWBACKS: It would be expensive to mine and mill enough olivine to make a
difference.
– Biochar –
Biochar is charcoal made by heating plant waste — rice straw, peanut
shells, wood scraps — over long periods in low-oxygen conditions. It can
store CO2 for long periods, and also enriches soil.
DRAWBACK: The scientific jury is still out on how quickly this method
could be scaled up, and on the stability of biochar used as a fertiliser.
– Solar radiation management –
Unlike other strategies, solar radiation management does not target CO2.
The goal is simple: prevent some of the sun’s rays from hitting the planet’s
surface, forcing them back up into space.
One idea is to inject or spray tiny reflective particles into the
stratosphere — possibly with balloons, aircraft or through giant tubes.
Scientists have also calculated ways to alter clouds that could help beat
the heat.
DRAWBACKS: Even if it works as intended, solar radiation management would
do nothing to reduce atmospheric CO2, which is making oceans too acidic.
There is also the danger of knock-on consequences, including changes in
rainfall patterns, and what scientists call “termination shock” — a sudden
warming if the system were to fail.
BSS/AFP/BZC/1945HRS