How Would Geo-Engineering Work?
The two main forms of geoengineering are solar radiation
management (SRM) and carbon dioxide removal (CDR). SRM reduces the effect of
climate change without reducing the level of greenhouse gases. CDR, on the
other hand, actively effects climate change through the removal of one of
highest emitted GHG’s: Carbon Dioxide.
Solar Radiation Management (SRM):
SRM effectively reduces the amount of sunlight absorbed by
the earth’s surface and so effectively reduces the subsequent warming effect. The
manual addition of reflective aerosols, like sulphate, in the atmosphere is one
of the main SRM techniques proposed amongst many other techniques (whitening of
roofs, rearing more reflective agriculture and placing reflective mirrors in
space – all to reflect solar radiation). If successful, SRM can modify the
climate in an aspect which could allow the mitigation of many centuries of
harmful emissions. Planet Earth has another chance.
The premise of reflective aerosols can be understood by
considering volcanic eruptions and the ejection of sulphates in the atmosphere that
trigger cooling through enhancement of radiation reflection (Timmreck 2012).
There are multiple risks attached to the SRM technique: reflective
aerosol addition to the atmosphere. Adding aerosols into the atmosphere would
bring about a rapid change in the atmosphere, driving cooling immediately –
however, this is based on the premise that aerosols will be replenished continually.
Where there is a failure, the climate would rapidly warm, at rates greater than
current. Further, the control of aerosols once released is out of the question,
meaning that global distribution could be uneven – resulting in uneven
modification of climate across the globe (Caldeira
et al 2013). This is hardly ethical, nor is it moral. Feasibility and the
uncertainty are the main drawbacks attached SRM geo-engineering.
Carbon Dioxide Removal (CDR):
Carbon Capture and Storage (CCS) is a technology that can capture
prior and current emitted carbon dioxide and store it in a suitable place (this can be in depleted oil fields or deep saline aquifers) –
effectively removing the driving causation of climate change. CCS is important to
initiate change in carbon dioxide levels, particularly where residence time is persistent
for thousands of years. CCS allows the possibility of climate change reversal.
The science behind CCS is briefly outlined in the video below (Figure 1):
(Figure 1: ZEP - Safe Storage: Closing the carbon loop - CO2 Capture and Storage)
Currently there are 22 projects, either under
construction or operational CCS projects. The risks behind CCS needs to be
understood to derive viability. Health risks are raised where the input of high
concentrations of carbon dioxide may contaminate surrounding areas–thus effecting
animals and humans alike. High concentrations can lead to sink lesions, memory
loss and death as seen in the release of carbon dioxide at Lake Nyos, Cameroon in
1986 where 100 000 tons approx. of carbon was released (Fogarty 2010).
Concerns also include whether CCS can reverse some of the damage borne through
anthropogenic emissions (Caldeira
et al 2013).
Geo-engineering has multiple risks attached to initiating
the schemes. CDR schemes are more appealing to me, tackling the situation at
the source. Further, unlike reflective aerosols that involve tampering with the
atmospheric climate – I believe we have done enough of that. Of course, there
are multiple other SRM techniques like raising plant reflectivity and placing
large mirrors in space – but these lack finesse in their ability to affect
global temperatures and viability, respectively. I believe that geo-engineering
schemes are valuable in line with renewable energies – seeking an alternative
away from carbon dioxide is vital whilst managing the current anthropogenic emissions
is the way forward to reversing climate change.
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