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News
and research about carbon dioxide removal and sunlight
reduction
The Sink & Mirror is a monthly
newsletter about carbon dioxide removal and sunlight
reduction, two possible approaches for limiting climate
change, together known as geoengineering. My name is Leo
Barasi. I recently wrote a book about climate change and public
opinion, and I started this newsletter as I'm interested
in debates about geoengineering as it moves into the
mainstream.
I've sent you this
newsletter because I think the subject may interest
you. Click here to unsubscribe if you would
rather not receive future
editions.
What happens if sunlight
reduction goes wrong?
Sunlight reduction is
a form of geoengineering where some of the sun’s energy
would be reflected back into space, for example with
reflective particles sprayed into the atmosphere. Two
recent scientific studies looked at what happens if
sunlight reduction is done badly. One study, in Nature Ecology &
Evolution, found that starting and then suddenly
stopping sunlight reduction would mean a fast
temperatures rise, endangering animals that can’t move
quickly enough. The other study, in Nature Communications,
suggests the effects of spraying reflective particles in
only one hemisphere - rather than globally - could pose
a tricky problem. Uneven spraying could lead to fewer
hurricanes in the Americas but also drought in Africa,
pointing to how sunlight reduction could be used to
benefit some parts of the world at the expense of other
places.
Some researchers criticised the media coverage -
pointing out that no-one advocates spraying particles in
only one hemisphere or suddenly stopping it. The risks
would be low, studies suggest, if the world
uses only a moderate amount of sunlight reduction
and manages it carefully. But why are we discussing
sunlight reduction in the first place? Because
governments might fail to cut emissions. It’s important
to understand what would happen if they also mis-managed
sunlight reduction.
Delaying carbon
dioxide removal could close off options
Some
options for carbon dioxide removal (CDR) are open now
but will fairly soon be closed, according to a comment article in Nature. Starting to
remove carbon dioxide now could give enough time to use
relatively attractive but slow methods, like large-scale
tree-planting. But if the world waits until later in the
century before using CDR to help meet the Paris
Agreement targets, it might have to rely on other
measures. This could include large-scale use of
bioenergy with carbon capture and storage (BECCS) which
might require vast areas of
land.
Large-scale carbon dioxide removal
may be unrealistic
The Paris Agreement set
ambitious goals for the world to limit warming to 1.5 or
2 degrees celsius, and, based on environmental and
economic models, most scientists think this will require
a significant contribution from CDR. But a new report argues the models are
unrealistic - they overestimate the amount of carbon
dioxide than can realistically be removed. It’s
particularly sceptical about BECCS, which the models
rely on heavily. As with the Nature comment, it shows
how important it is to understand the potential and
problems with CDR now, rather than leaving it as a
question for the future.
Underwater walls
to cut sea-level rise
An article in the Atlantic looks at the
idea of building underwater walls in front of major
glaciers, to slow their melt and so limit sea-level
rise. It would be an enormous engineering challenge,
including needing submarines to build a 60-mile
underwater wall in Antarctica. But it would still only
tackle one symptom of climate change, rather than its
causes. The oceans would continue to acidify and the
world would face all the other consequences of climate
change.
Political backing for
geoengineering
Some US politicians are
getting interested in geoengineering. The budget bill, signed in February,
includes tax credits for carbon removal. Separately,
Lamar Smith, a climate-science denying Congressman who
chairs the House Science Committee, suggested sunlight
reduction could be a solution. Meanwhile, a US
House Bill would mean funding for the
National Academies to propose research into sunlight
reduction. The Bill was introduced by a Democrat, Jerry
McNerney, who is outspoken on the need to deal with
climate change.
I've sent you this
newsletter because I think the subject may interest
you. Click here to unsubscribe if you would
rather not receive future
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