Climate engineering: is it something we should be starting to think seriously about?

by Christopher Brodrick

Despite the global implementation of emission reduction policies and sustainable development protocols, greenhouse gas emissions continue to increase steadily. Taking into account, inter alia, the rapid development occurring in China and India, it is looking increasingly unlikely that emissions targets for upcoming decades will be met… So, what to do?

Enter Climate engineering. Not necessarily a new concept, but perhaps it isn’t being dismissed out of hand quite as readily as it was five years ago. Scientists, inventors, policy makers: all are genuinely interested in ascertaining whether or not there is an ‘artificial’ climate modulator that could potentially act on a grand enough scale to save our skins.

There are two broad categories of climate engineering techniques: carbon dioxide reduction and radiation management[i]. The former aims to scavenge carbon dioxide from the atmosphere by adjusting planetary conditions, while the latter aims to favourably alter the Earth’s energy balance by reducing the amount of solar radiation entering our atmosphere.

Let’s take a look at some possible climate engineering programmes:

Radiation management techniques[ii]:

1. Space mirrors – large reflective objects are sent into orbit in order to reflect a portion of solar radiation away from the Earth. Drawbacks: unknown weather effects; potentially very expensive.
2. Reflective crops – planting crops that reflect rather than absorb solar radiation. Drawbacks: need large areas of land; unlikely to make an appreciable difference.
3. Aerosols – particles ejected into the atmosphere act to reflect solar radiation. Drawbacks: unknown weather effects; risk of ozone depletion.
4. Cloud seeding – very white clouds created by the atomisation of sea water act to reflect solar radiation. Drawback: unknown weather effects.

Carbon dioxide reduction techniques[iii]:

1. Reforestation – trees planted to sequester CO₂. Drawbacks: large areas of land required; can actually act to raise temperatures due to decreased land surface albedo.
2. Ocean fertilization – iron filings added to the oceans to stimulate CO₂-consuming plankton. Drawbacks: unknown effects on ecosystems; alteration of oxygen minimum zones.
3. Ocean alkalisation – lime added to the oceans to facilitate greater capacity for CO₂ sequestration. Drawback: unknown effects on ecosystems.
4. Ocean upwelling[iv] – long pipes pump up deep ocean water – cold and nutrient-rich – to replace surface layer water. This allows for more direct carbon uptake from the atmosphere as well as stimulating plant growth, thereby sequestering further CO₂. Drawbacks: altering the salt and temperature layers of the ocean could have potentially devastating consequences; ocean currents will be affected.

Arguably, the techniques which have the greatest potential to curb warming are aerosols and cloud seeding (radiation management), and ocean upwelling (carbon dioxide reduction).

Theoretically, with the aerosol technique, it is possible to grow diminishing polar ice caps, with a relatively short time period before the manifestation of appreciable results (approximately a few months, if burned sulphur particles were injected into the stratosphere)[v]. Cloud seeing has the added benefit that, if things happen to turn pear-shaped, it can be stopped immediately, with almost all the salt particles either being rained- or settled out of the atmosphere within ten days[vi].

Now the bad news. If an established large scale radiation management programme were suddenly halted, temperatures would rise at a rate very much faster than they would under ‘normal’ conditions. In all likelihood, this would leap-frog any projected temperature rise for a given emission scenario[vii].

The ocean upwelling programme could also have dire consequences. Both the salt and temperature characteristics of the ocean would be radically changed, having a significant effect on ocean currents[viii]. There is no room for error here: if anything were to go wrong, the surplus heat stored by the altered surface layer would be released back into the atmosphere, causing temperatures to sky-rocket.

Some pretty scary consequences then if things don’t quite go to plan. Are we at a point yet where we can more confidently bandy about the phrase “desperate times call for desperate measures” or is this whole climate engineering notion a step too far? Fortunately, for the more prudent of those among us, MPs from the Science and Technology committee in the UK have urged international regulation in order to prevent individual countries from setting in place programmes to manipulate the Earth’s climate[ix]. It is suggested that no country should be allowed to take such action without consultation with the UN[x].

 

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